Merge remote-tracking branch 'origin/trunk' into hostgen

Cargo.lock

@@ -468,9 +468,9 @@ dependencies = [
 
 [[package]]
 name = "clap"
-version = "3.1.15"
+version = "3.1.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "85a35a599b11c089a7f49105658d089b8f2cf0882993c17daf6de15285c2c35d"
+checksum = "47582c09be7c8b32c0ab3a6181825ababb713fde6fff20fc573a3870dd45c6a0"
 dependencies = [
  "atty",
  "bitflags",
@@ -516,6 +516,7 @@ name = "cli_utils"
 version = "0.1.0"
 dependencies = [
  "bumpalo",
+ "const_format",
  "criterion 0.3.5 (git+https://github.com/Anton-4/criterion.rs)",
  "rlimit",
  "roc_cli",
@@ -1674,9 +1675,9 @@ dependencies = [
 
 [[package]]
 name = "glyph_brush"
-version = "0.7.3"
+version = "0.7.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "21932fbf719272848eec4583740d978203c6e7da4c4e203358f5b95946c97409"
+checksum = "a69c65dd1f1fbb6209aa00f78636e436ad0a55b7d8e5de886d00720dcad9c6e2"
 dependencies = [
  "glyph_brush_draw_cache",
  "glyph_brush_layout",
@@ -1865,12 +1866,9 @@ dependencies = [
 
 [[package]]
 name = "indoc"
-version = "1.0.4"
+version = "1.0.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e7906a9fababaeacb774f72410e497a1d18de916322e33797bb2cd29baa23c9e"
+checksum = "05a0bd019339e5d968b37855180087b7b9d512c5046fbd244cf8c95687927d6e"
-dependencies = [
- "unindent",
-]
 
 [[package]]
 name = "inkwell"
@@ -2688,9 +2686,9 @@ checksum = "624a8340c38c1b80fd549087862da4ba43e08858af025b236e509b6649fc13d5"
 
 [[package]]
 name = "ordered-float"
-version = "2.10.0"
+version = "3.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7940cf2ca942593318d07fcf2596cdca60a85c9e7fab408a5e21a4f9dcd40d87"
+checksum = "96bcbab4bfea7a59c2c0fe47211a1ac4e3e96bea6eb446d704f310bc5c732ae2"
 dependencies = [
  "num-traits",
 ]
@@ -3085,9 +3083,9 @@ checksum = "dbf0c48bc1d91375ae5c3cd81e3722dff1abcf81a30960240640d223f59fe0e5"
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.37"
+version = "1.0.38"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ec757218438d5fda206afc041538b2f6d889286160d649a86a24d37e1235afd1"
+checksum = "9027b48e9d4c9175fa2218adf3557f91c1137021739951d4932f5f8268ac48aa"
 dependencies = [
  "unicode-xid",
 ]
@@ -3435,7 +3433,7 @@ name = "roc-bindgen"
 version = "0.1.0"
 dependencies = [
  "bumpalo",
- "clap 3.1.15",
+ "clap 3.1.17",
  "indoc",
  "pretty_assertions",
  "roc_builtins",
@@ -3546,7 +3544,6 @@ dependencies = [
  "bumpalo",
  "indoc",
  "pretty_assertions",
- "roc_builtins",
  "roc_collections",
  "roc_error_macros",
  "roc_exhaustive",
@@ -3556,7 +3553,6 @@ dependencies = [
  "roc_region",
  "roc_types",
  "static_assertions 1.1.0",
- "ven_graph",
 ]
 
 [[package]]
@@ -3564,7 +3560,7 @@ name = "roc_cli"
 version = "0.1.0"
 dependencies = [
  "bumpalo",
- "clap 3.1.15",
+ "clap 3.1.17",
  "cli_utils",
  "const_format",
  "criterion 0.3.5 (git+https://github.com/Anton-4/criterion.rs)",
@@ -3590,6 +3586,8 @@ dependencies = [
  "roc_target",
  "roc_test_utils",
  "serial_test",
+ "strum",
+ "strum_macros",
  "target-lexicon",
  "tempfile",
  "wasmer",
@@ -3645,7 +3643,6 @@ name = "roc_docs"
 version = "0.1.0"
 dependencies = [
  "bumpalo",
- "indoc",
  "peg",
  "pretty_assertions",
  "pulldown-cmark",
@@ -3663,8 +3660,6 @@ dependencies = [
  "roc_target",
  "roc_types",
  "snafu",
- "tempfile",
- "uuid",
 ]
 
 [[package]]
@@ -3813,9 +3808,6 @@ dependencies = [
 [[package]]
 name = "roc_ident"
 version = "0.1.0"
-dependencies = [
- "arrayvec 0.7.2",
-]
 
 [[package]]
 name = "roc_linker"
@@ -3823,7 +3815,7 @@ version = "0.1.0"
 dependencies = [
  "bincode",
  "bumpalo",
- "clap 3.1.15",
+ "clap 3.1.17",
  "iced-x86",
  "memmap2 0.5.3",
  "object 0.26.2",
@@ -3858,8 +3850,6 @@ dependencies = [
  "crossbeam",
  "indoc",
  "maplit",
- "morphic_lib",
- "num_cpus",
  "parking_lot 0.12.0",
  "pretty_assertions",
  "roc_builtins",
@@ -3879,7 +3869,6 @@ dependencies = [
  "roc_test_utils",
  "roc_types",
  "roc_unify",
- "tempfile",
  "ven_pretty",
 ]
 
@@ -3887,7 +3876,6 @@ dependencies = [
 name = "roc_module"
 version = "0.1.0"
 dependencies = [
- "arrayvec 0.7.2",
  "bumpalo",
  "lazy_static",
  "roc_collections",
@@ -3904,7 +3892,6 @@ version = "0.1.0"
 dependencies = [
  "bumpalo",
  "hashbrown 0.11.2",
- "morphic_lib",
  "roc_builtins",
  "roc_can",
  "roc_collections",
@@ -4047,7 +4034,6 @@ dependencies = [
  "roc_target",
  "roc_test_utils",
  "roc_types",
- "tempfile",
  "ven_pretty",
 ]
 
@@ -4690,6 +4676,25 @@ version = "0.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "73473c0e59e6d5812c5dfe2a064a6444949f089e20eec9a2e5506596494e4623"
 
+[[package]]
+name = "strum"
+version = "0.24.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e96acfc1b70604b8b2f1ffa4c57e59176c7dbb05d556c71ecd2f5498a1dee7f8"
+
+[[package]]
+name = "strum_macros"
+version = "0.24.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6878079b17446e4d3eba6192bb0a2950d5b14f0ed8424b852310e5a94345d0ef"
+dependencies = [
+ "heck",
+ "proc-macro2",
+ "quote",
+ "rustversion",
+ "syn",
+]
+
 [[package]]
 name = "syn"
 version = "1.0.92"
@@ -4778,7 +4783,6 @@ version = "0.1.0"
 dependencies = [
  "bumpalo",
  "indoc",
- "pretty_assertions",
  "roc_builtins",
  "roc_can",
  "roc_collections",
@@ -5016,12 +5020,6 @@ version = "0.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "957e51f3646910546462e67d5f7599b9e4fb8acdd304b087a6494730f9eebf04"
 
-[[package]]
-name = "unindent"
-version = "0.1.8"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "514672a55d7380da379785a4d70ca8386c8883ff7eaae877be4d2081cebe73d8"
-
 [[package]]
 name = "utf8parse"
 version = "0.2.0"

bindgen/src/main.rs

@@ -56,7 +56,7 @@ pub fn main() {
         }
     };
 
-    match load_types(input_path.clone(), &cwd, Threading::Multi) {
+    match load_types(input_path.clone(), &cwd, Threading::AllAvailable) {
         Ok(types) => {
             let mut buf;
 

cli/Cargo.toml

@@ -85,6 +85,8 @@ indoc = "1.0.3"
 serial_test = "0.5.1"
 criterion = { git = "https://github.com/Anton-4/criterion.rs"}
 cli_utils = { path = "../cli_utils" }
+strum = "0.24.0"
+strum_macros = "0.24"
 
 # Wasmer singlepass compiler only works on x86_64.
 [target.'cfg(target_arch = "x86_64")'.dev-dependencies]

cli/src/build.rs

@@ -350,6 +350,7 @@ pub fn check_file(
     src_dir: PathBuf,
     roc_file_path: PathBuf,
     emit_timings: bool,
+    threading: Threading,
 ) -> Result<(program::Problems, Duration), LoadingProblem> {
     let compilation_start = SystemTime::now();
 
@@ -368,7 +369,7 @@ pub fn check_file(
         target_info,
         // TODO: expose this from CLI?
         RenderTarget::ColorTerminal,
-        Threading::Multi,
+        threading,
     )?;
 
     let buf = &mut String::with_capacity(1024);

cli/src/format.rs

@@ -2,29 +2,17 @@ use std::ffi::OsStr;
 use std::path::{Path, PathBuf};
 
 use crate::FormatMode;
-use bumpalo::collections::Vec;
 use bumpalo::Bump;
 use roc_error_macros::{internal_error, user_error};
 use roc_fmt::def::fmt_def;
 use roc_fmt::module::fmt_module;
-use roc_fmt::Buf;
+use roc_fmt::spaces::RemoveSpaces;
-use roc_module::called_via::{BinOp, UnaryOp};
+use roc_fmt::{Ast, Buf};
-use roc_parse::ast::{
-    AbilityMember, AssignedField, Collection, Expr, Has, HasClause, Pattern, Spaced, StrLiteral,
-    StrSegment, Tag, TypeAnnotation, TypeDef, TypeHeader, ValueDef, WhenBranch,
-};
-use roc_parse::header::{
-    AppHeader, ExposedName, HostedHeader, ImportsEntry, InterfaceHeader, ModuleName, PackageEntry,
-    PackageName, PlatformHeader, PlatformRequires, To, TypedIdent,
-};
 use roc_parse::{
-    ast::{Def, Module},
-    ident::UppercaseIdent,
     module::{self, module_defs},
     parser::{Parser, SyntaxError},
     state::State,
 };
-use roc_region::all::{Loc, Region};
 
 fn flatten_directories(files: std::vec::Vec<PathBuf>) -> std::vec::Vec<PathBuf> {
     let mut to_flatten = files;
@@ -166,12 +154,6 @@ pub fn format(files: std::vec::Vec<PathBuf>, mode: FormatMode) -> Result<(), Str
     Ok(())
 }
 
-#[derive(Debug, PartialEq)]
-struct Ast<'a> {
-    module: Module<'a>,
-    defs: Vec<'a, Loc<Def<'a>>>,
-}
-
 fn parse_all<'a>(arena: &'a Bump, src: &'a str) -> Result<Ast<'a>, SyntaxError<'a>> {
     let (module, state) = module::parse_header(arena, State::new(src.as_bytes()))
         .map_err(|e| SyntaxError::Header(e.problem))?;
@@ -189,575 +171,3 @@ fn fmt_all<'a>(arena: &'a Bump, buf: &mut Buf<'a>, ast: &'a Ast) {
 
     buf.fmt_end_of_file();
 }
-
-/// RemoveSpaces normalizes the ast to something that we _expect_ to be invariant under formatting.
-///
-/// Currently this consists of:
-/// * Removing newlines
-/// * Removing comments
-/// * Removing parens in Exprs
-///
-/// Long term, we actuall want this transform to preserve comments (so we can assert they're maintained by formatting)
-/// - but there are currently several bugs where they're _not_ preserved.
-/// TODO: ensure formatting retains comments
-trait RemoveSpaces<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self;
-}
-
-impl<'a> RemoveSpaces<'a> for Ast<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        Ast {
-            module: self.module.remove_spaces(arena),
-            defs: {
-                let mut defs = Vec::with_capacity_in(self.defs.len(), arena);
-                for d in &self.defs {
-                    defs.push(d.remove_spaces(arena))
-                }
-                defs
-            },
-        }
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for Module<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        match self {
-            Module::Interface { header } => Module::Interface {
-                header: InterfaceHeader {
-                    name: header.name.remove_spaces(arena),
-                    exposes: header.exposes.remove_spaces(arena),
-                    imports: header.imports.remove_spaces(arena),
-                    before_header: &[],
-                    after_interface_keyword: &[],
-                    before_exposes: &[],
-                    after_exposes: &[],
-                    before_imports: &[],
-                    after_imports: &[],
-                },
-            },
-            Module::App { header } => Module::App {
-                header: AppHeader {
-                    name: header.name.remove_spaces(arena),
-                    packages: header.packages.remove_spaces(arena),
-                    imports: header.imports.remove_spaces(arena),
-                    provides: header.provides.remove_spaces(arena),
-                    provides_types: header.provides_types.map(|ts| ts.remove_spaces(arena)),
-                    to: header.to.remove_spaces(arena),
-                    before_header: &[],
-                    after_app_keyword: &[],
-                    before_packages: &[],
-                    after_packages: &[],
-                    before_imports: &[],
-                    after_imports: &[],
-                    before_provides: &[],
-                    after_provides: &[],
-                    before_to: &[],
-                    after_to: &[],
-                },
-            },
-            Module::Platform { header } => Module::Platform {
-                header: PlatformHeader {
-                    name: header.name.remove_spaces(arena),
-                    requires: header.requires.remove_spaces(arena),
-                    exposes: header.exposes.remove_spaces(arena),
-                    packages: header.packages.remove_spaces(arena),
-                    imports: header.imports.remove_spaces(arena),
-                    provides: header.provides.remove_spaces(arena),
-                    before_header: &[],
-                    after_platform_keyword: &[],
-                    before_requires: &[],
-                    after_requires: &[],
-                    before_exposes: &[],
-                    after_exposes: &[],
-                    before_packages: &[],
-                    after_packages: &[],
-                    before_imports: &[],
-                    after_imports: &[],
-                    before_provides: &[],
-                    after_provides: &[],
-                },
-            },
-            Module::Hosted { header } => Module::Hosted {
-                header: HostedHeader {
-                    name: header.name.remove_spaces(arena),
-                    exposes: header.exposes.remove_spaces(arena),
-                    imports: header.imports.remove_spaces(arena),
-                    generates: header.generates.remove_spaces(arena),
-                    generates_with: header.generates_with.remove_spaces(arena),
-                    before_header: &[],
-                    after_hosted_keyword: &[],
-                    before_exposes: &[],
-                    after_exposes: &[],
-                    before_imports: &[],
-                    after_imports: &[],
-                    before_generates: &[],
-                    after_generates: &[],
-                    before_with: &[],
-                    after_with: &[],
-                },
-            },
-        }
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for &'a str {
-    fn remove_spaces(&self, _arena: &'a Bump) -> Self {
-        self
-    }
-}
-
-impl<'a, T: RemoveSpaces<'a> + Copy> RemoveSpaces<'a> for Spaced<'a, T> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        match *self {
-            Spaced::Item(a) => Spaced::Item(a.remove_spaces(arena)),
-            Spaced::SpaceBefore(a, _) => a.remove_spaces(arena),
-            Spaced::SpaceAfter(a, _) => a.remove_spaces(arena),
-        }
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for ExposedName<'a> {
-    fn remove_spaces(&self, _arena: &'a Bump) -> Self {
-        *self
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for ModuleName<'a> {
-    fn remove_spaces(&self, _arena: &'a Bump) -> Self {
-        *self
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for PackageName<'a> {
-    fn remove_spaces(&self, _arena: &'a Bump) -> Self {
-        *self
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for To<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        match *self {
-            To::ExistingPackage(a) => To::ExistingPackage(a),
-            To::NewPackage(a) => To::NewPackage(a.remove_spaces(arena)),
-        }
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for TypedIdent<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        TypedIdent {
-            ident: self.ident.remove_spaces(arena),
-            spaces_before_colon: &[],
-            ann: self.ann.remove_spaces(arena),
-        }
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for PlatformRequires<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        PlatformRequires {
-            rigids: self.rigids.remove_spaces(arena),
-            signature: self.signature.remove_spaces(arena),
-        }
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for UppercaseIdent<'a> {
-    fn remove_spaces(&self, _arena: &'a Bump) -> Self {
-        *self
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for PackageEntry<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        PackageEntry {
-            shorthand: self.shorthand,
-            spaces_after_shorthand: &[],
-            package_name: self.package_name.remove_spaces(arena),
-        }
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for ImportsEntry<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        match *self {
-            ImportsEntry::Module(a, b) => ImportsEntry::Module(a, b.remove_spaces(arena)),
-            ImportsEntry::Package(a, b, c) => ImportsEntry::Package(a, b, c.remove_spaces(arena)),
-        }
-    }
-}
-
-impl<'a, T: RemoveSpaces<'a>> RemoveSpaces<'a> for Option<T> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        self.as_ref().map(|a| a.remove_spaces(arena))
-    }
-}
-
-impl<'a, T: RemoveSpaces<'a> + std::fmt::Debug> RemoveSpaces<'a> for Loc<T> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        let res = self.value.remove_spaces(arena);
-        Loc::at(Region::zero(), res)
-    }
-}
-
-impl<'a, A: RemoveSpaces<'a>, B: RemoveSpaces<'a>> RemoveSpaces<'a> for (A, B) {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        (self.0.remove_spaces(arena), self.1.remove_spaces(arena))
-    }
-}
-
-impl<'a, T: RemoveSpaces<'a>> RemoveSpaces<'a> for Collection<'a, T> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        let mut items = Vec::with_capacity_in(self.items.len(), arena);
-        for item in self.items {
-            items.push(item.remove_spaces(arena));
-        }
-        Collection::with_items(items.into_bump_slice())
-    }
-}
-
-impl<'a, T: RemoveSpaces<'a> + std::fmt::Debug> RemoveSpaces<'a> for &'a [T] {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        let mut items = Vec::with_capacity_in(self.len(), arena);
-        for item in *self {
-            let res = item.remove_spaces(arena);
-            items.push(res);
-        }
-        items.into_bump_slice()
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for UnaryOp {
-    fn remove_spaces(&self, _arena: &'a Bump) -> Self {
-        *self
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for BinOp {
-    fn remove_spaces(&self, _arena: &'a Bump) -> Self {
-        *self
-    }
-}
-
-impl<'a, T: RemoveSpaces<'a>> RemoveSpaces<'a> for &'a T {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        arena.alloc((*self).remove_spaces(arena))
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for TypeDef<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        use TypeDef::*;
-
-        match *self {
-            Alias {
-                header: TypeHeader { name, vars },
-                ann,
-            } => Alias {
-                header: TypeHeader {
-                    name: name.remove_spaces(arena),
-                    vars: vars.remove_spaces(arena),
-                },
-                ann: ann.remove_spaces(arena),
-            },
-            Opaque {
-                header: TypeHeader { name, vars },
-                typ,
-            } => Opaque {
-                header: TypeHeader {
-                    name: name.remove_spaces(arena),
-                    vars: vars.remove_spaces(arena),
-                },
-                typ: typ.remove_spaces(arena),
-            },
-            Ability {
-                header: TypeHeader { name, vars },
-                loc_has,
-                members,
-            } => Ability {
-                header: TypeHeader {
-                    name: name.remove_spaces(arena),
-                    vars: vars.remove_spaces(arena),
-                },
-                loc_has: loc_has.remove_spaces(arena),
-                members: members.remove_spaces(arena),
-            },
-        }
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for ValueDef<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        use ValueDef::*;
-
-        match *self {
-            Annotation(a, b) => Annotation(a.remove_spaces(arena), b.remove_spaces(arena)),
-            Body(a, b) => Body(
-                arena.alloc(a.remove_spaces(arena)),
-                arena.alloc(b.remove_spaces(arena)),
-            ),
-            AnnotatedBody {
-                ann_pattern,
-                ann_type,
-                comment: _,
-                body_pattern,
-                body_expr,
-            } => AnnotatedBody {
-                ann_pattern: arena.alloc(ann_pattern.remove_spaces(arena)),
-                ann_type: arena.alloc(ann_type.remove_spaces(arena)),
-                comment: None,
-                body_pattern: arena.alloc(body_pattern.remove_spaces(arena)),
-                body_expr: arena.alloc(body_expr.remove_spaces(arena)),
-            },
-            Expect(a) => Expect(arena.alloc(a.remove_spaces(arena))),
-        }
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for Def<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        match *self {
-            Def::Type(def) => Def::Type(def.remove_spaces(arena)),
-            Def::Value(def) => Def::Value(def.remove_spaces(arena)),
-            Def::NotYetImplemented(a) => Def::NotYetImplemented(a),
-            Def::SpaceBefore(a, _) | Def::SpaceAfter(a, _) => a.remove_spaces(arena),
-        }
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for Has<'a> {
-    fn remove_spaces(&self, _arena: &'a Bump) -> Self {
-        Has::Has
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for AbilityMember<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        AbilityMember {
-            name: self.name.remove_spaces(arena),
-            typ: self.typ.remove_spaces(arena),
-        }
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for WhenBranch<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        WhenBranch {
-            patterns: self.patterns.remove_spaces(arena),
-            value: self.value.remove_spaces(arena),
-            guard: self.guard.remove_spaces(arena),
-        }
-    }
-}
-
-impl<'a, T: RemoveSpaces<'a> + Copy + std::fmt::Debug> RemoveSpaces<'a> for AssignedField<'a, T> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        match *self {
-            AssignedField::RequiredValue(a, _, c) => AssignedField::RequiredValue(
-                a.remove_spaces(arena),
-                arena.alloc([]),
-                arena.alloc(c.remove_spaces(arena)),
-            ),
-            AssignedField::OptionalValue(a, _, c) => AssignedField::OptionalValue(
-                a.remove_spaces(arena),
-                arena.alloc([]),
-                arena.alloc(c.remove_spaces(arena)),
-            ),
-            AssignedField::LabelOnly(a) => AssignedField::LabelOnly(a.remove_spaces(arena)),
-            AssignedField::Malformed(a) => AssignedField::Malformed(a),
-            AssignedField::SpaceBefore(a, _) => a.remove_spaces(arena),
-            AssignedField::SpaceAfter(a, _) => a.remove_spaces(arena),
-        }
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for StrLiteral<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        match *self {
-            StrLiteral::PlainLine(t) => StrLiteral::PlainLine(t),
-            StrLiteral::Line(t) => StrLiteral::Line(t.remove_spaces(arena)),
-            StrLiteral::Block(t) => StrLiteral::Block(t.remove_spaces(arena)),
-        }
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for StrSegment<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        match *self {
-            StrSegment::Plaintext(t) => StrSegment::Plaintext(t),
-            StrSegment::Unicode(t) => StrSegment::Unicode(t.remove_spaces(arena)),
-            StrSegment::EscapedChar(c) => StrSegment::EscapedChar(c),
-            StrSegment::Interpolated(t) => StrSegment::Interpolated(t.remove_spaces(arena)),
-        }
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for Expr<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        match *self {
-            Expr::Float(a) => Expr::Float(a),
-            Expr::Num(a) => Expr::Num(a),
-            Expr::NonBase10Int {
-                string,
-                base,
-                is_negative,
-            } => Expr::NonBase10Int {
-                string,
-                base,
-                is_negative,
-            },
-            Expr::Str(a) => Expr::Str(a.remove_spaces(arena)),
-            Expr::Access(a, b) => Expr::Access(arena.alloc(a.remove_spaces(arena)), b),
-            Expr::AccessorFunction(a) => Expr::AccessorFunction(a),
-            Expr::List(a) => Expr::List(a.remove_spaces(arena)),
-            Expr::RecordUpdate { update, fields } => Expr::RecordUpdate {
-                update: arena.alloc(update.remove_spaces(arena)),
-                fields: fields.remove_spaces(arena),
-            },
-            Expr::Record(a) => Expr::Record(a.remove_spaces(arena)),
-            Expr::Var { module_name, ident } => Expr::Var { module_name, ident },
-            Expr::Underscore(a) => Expr::Underscore(a),
-            Expr::Tag(a) => Expr::Tag(a),
-            Expr::OpaqueRef(a) => Expr::OpaqueRef(a),
-            Expr::Closure(a, b) => Expr::Closure(
-                arena.alloc(a.remove_spaces(arena)),
-                arena.alloc(b.remove_spaces(arena)),
-            ),
-            Expr::Defs(a, b) => {
-                Expr::Defs(a.remove_spaces(arena), arena.alloc(b.remove_spaces(arena)))
-            }
-            Expr::Backpassing(a, b, c) => Expr::Backpassing(
-                arena.alloc(a.remove_spaces(arena)),
-                arena.alloc(b.remove_spaces(arena)),
-                arena.alloc(c.remove_spaces(arena)),
-            ),
-            Expr::Expect(a, b) => Expr::Expect(
-                arena.alloc(a.remove_spaces(arena)),
-                arena.alloc(b.remove_spaces(arena)),
-            ),
-            Expr::Apply(a, b, c) => Expr::Apply(
-                arena.alloc(a.remove_spaces(arena)),
-                b.remove_spaces(arena),
-                c,
-            ),
-            Expr::BinOps(a, b) => {
-                Expr::BinOps(a.remove_spaces(arena), arena.alloc(b.remove_spaces(arena)))
-            }
-            Expr::UnaryOp(a, b) => {
-                Expr::UnaryOp(arena.alloc(a.remove_spaces(arena)), b.remove_spaces(arena))
-            }
-            Expr::If(a, b) => Expr::If(a.remove_spaces(arena), arena.alloc(b.remove_spaces(arena))),
-            Expr::When(a, b) => {
-                Expr::When(arena.alloc(a.remove_spaces(arena)), b.remove_spaces(arena))
-            }
-            Expr::ParensAround(a) => {
-                // The formatter can remove redundant parentheses, so also remove these when normalizing for comparison.
-                a.remove_spaces(arena)
-            }
-            Expr::MalformedIdent(a, b) => Expr::MalformedIdent(a, b),
-            Expr::MalformedClosure => Expr::MalformedClosure,
-            Expr::PrecedenceConflict(a) => Expr::PrecedenceConflict(a),
-            Expr::SpaceBefore(a, _) => a.remove_spaces(arena),
-            Expr::SpaceAfter(a, _) => a.remove_spaces(arena),
-            Expr::SingleQuote(a) => Expr::Num(a),
-        }
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for Pattern<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        match *self {
-            Pattern::Identifier(a) => Pattern::Identifier(a),
-            Pattern::Tag(a) => Pattern::Tag(a),
-            Pattern::OpaqueRef(a) => Pattern::OpaqueRef(a),
-            Pattern::Apply(a, b) => Pattern::Apply(
-                arena.alloc(a.remove_spaces(arena)),
-                arena.alloc(b.remove_spaces(arena)),
-            ),
-            Pattern::RecordDestructure(a) => Pattern::RecordDestructure(a.remove_spaces(arena)),
-            Pattern::RequiredField(a, b) => {
-                Pattern::RequiredField(a, arena.alloc(b.remove_spaces(arena)))
-            }
-            Pattern::OptionalField(a, b) => {
-                Pattern::OptionalField(a, arena.alloc(b.remove_spaces(arena)))
-            }
-            Pattern::NumLiteral(a) => Pattern::NumLiteral(a),
-            Pattern::NonBase10Literal {
-                string,
-                base,
-                is_negative,
-            } => Pattern::NonBase10Literal {
-                string,
-                base,
-                is_negative,
-            },
-            Pattern::FloatLiteral(a) => Pattern::FloatLiteral(a),
-            Pattern::StrLiteral(a) => Pattern::StrLiteral(a),
-            Pattern::Underscore(a) => Pattern::Underscore(a),
-            Pattern::Malformed(a) => Pattern::Malformed(a),
-            Pattern::MalformedIdent(a, b) => Pattern::MalformedIdent(a, b),
-            Pattern::QualifiedIdentifier { module_name, ident } => {
-                Pattern::QualifiedIdentifier { module_name, ident }
-            }
-            Pattern::SpaceBefore(a, _) => a.remove_spaces(arena),
-            Pattern::SpaceAfter(a, _) => a.remove_spaces(arena),
-            Pattern::SingleQuote(a) => Pattern::NumLiteral(a),
-        }
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for TypeAnnotation<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        match *self {
-            TypeAnnotation::Function(a, b) => TypeAnnotation::Function(
-                arena.alloc(a.remove_spaces(arena)),
-                arena.alloc(b.remove_spaces(arena)),
-            ),
-            TypeAnnotation::Apply(a, b, c) => TypeAnnotation::Apply(a, b, c.remove_spaces(arena)),
-            TypeAnnotation::BoundVariable(a) => TypeAnnotation::BoundVariable(a),
-            TypeAnnotation::As(a, _, c) => {
-                TypeAnnotation::As(arena.alloc(a.remove_spaces(arena)), &[], c)
-            }
-            TypeAnnotation::Record { fields, ext } => TypeAnnotation::Record {
-                fields: fields.remove_spaces(arena),
-                ext: ext.remove_spaces(arena),
-            },
-            TypeAnnotation::TagUnion { ext, tags } => TypeAnnotation::TagUnion {
-                ext: ext.remove_spaces(arena),
-                tags: tags.remove_spaces(arena),
-            },
-            TypeAnnotation::Inferred => TypeAnnotation::Inferred,
-            TypeAnnotation::Wildcard => TypeAnnotation::Wildcard,
-            TypeAnnotation::Where(annot, has_clauses) => TypeAnnotation::Where(
-                arena.alloc(annot.remove_spaces(arena)),
-                arena.alloc(has_clauses.remove_spaces(arena)),
-            ),
-            TypeAnnotation::SpaceBefore(a, _) => a.remove_spaces(arena),
-            TypeAnnotation::SpaceAfter(a, _) => a.remove_spaces(arena),
-            TypeAnnotation::Malformed(a) => TypeAnnotation::Malformed(a),
-        }
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for HasClause<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        HasClause {
-            var: self.var.remove_spaces(arena),
-            ability: self.ability.remove_spaces(arena),
-        }
-    }
-}
-
-impl<'a> RemoveSpaces<'a> for Tag<'a> {
-    fn remove_spaces(&self, arena: &'a Bump) -> Self {
-        match *self {
-            Tag::Apply { name, args } => Tag::Apply {
-                name: name.remove_spaces(arena),
-                args: args.remove_spaces(arena),
-            },
-            Tag::Malformed(a) => Tag::Malformed(a),
-            Tag::SpaceBefore(a, _) => a.remove_spaces(arena),
-            Tag::SpaceAfter(a, _) => a.remove_spaces(arena),
-        }
-    }
-}

cli/src/lib.rs

@@ -3,16 +3,15 @@ extern crate const_format;
 
 use build::BuiltFile;
 use bumpalo::Bump;
-use clap::Command;
+use clap::{Arg, ArgMatches, Command};
-use clap::{Arg, ArgMatches};
 use roc_build::link::LinkType;
 use roc_error_macros::user_error;
 use roc_load::{LoadingProblem, Threading};
 use roc_mono::ir::OptLevel;
 use std::env;
+use std::ffi::OsStr;
 use std::io;
-use std::path::Path;
+use std::path::{Path, PathBuf};
-use std::path::PathBuf;
 use std::process;
 use target_lexicon::BinaryFormat;
 use target_lexicon::{
@@ -35,6 +34,7 @@ pub const CMD_FORMAT: &str = "format";
 pub const FLAG_DEBUG: &str = "debug";
 pub const FLAG_DEV: &str = "dev";
 pub const FLAG_OPTIMIZE: &str = "optimize";
+pub const FLAG_MAX_THREADS: &str = "max-threads";
 pub const FLAG_OPT_SIZE: &str = "opt-size";
 pub const FLAG_LIB: &str = "lib";
 pub const FLAG_NO_LINK: &str = "no-link";
@@ -58,6 +58,14 @@ pub fn build_app<'a>() -> Command<'a> {
         .requires(ROC_FILE)
         .required(false);
 
+    let flag_max_threads = Arg::new(FLAG_MAX_THREADS)
+        .long(FLAG_MAX_THREADS)
+        .help("Limit the number of threads (and hence cores) used during compilation.")
+        .requires(ROC_FILE)
+        .takes_value(true)
+        .validator(|s| s.parse::<usize>())
+        .required(false);
+
     let flag_opt_size = Arg::new(FLAG_OPT_SIZE)
         .long(FLAG_OPT_SIZE)
         .help("Optimize the compiled program to have a small binary size. (Optimization takes time to complete.)")
@@ -96,12 +104,23 @@ pub fn build_app<'a>() -> Command<'a> {
         .possible_values(["true", "false"])
         .required(false);
 
+    let roc_file_to_run = Arg::new(ROC_FILE)
+        .help("The .roc file of an app to run")
+        .allow_invalid_utf8(true);
+
+    let args_for_app = Arg::new(ARGS_FOR_APP)
+        .help("Arguments to pass into the app being run")
+        .requires(ROC_FILE)
+        .allow_invalid_utf8(true)
+        .multiple_values(true);
+
     let app = Command::new("roc")
         .version(concatcp!(VERSION, "\n"))
         .about("Runs the given .roc file, if there are no compilation errors.\nUse one of the SUBCOMMANDS below to do something else!")
         .subcommand(Command::new(CMD_BUILD)
             .about("Build a binary from the given .roc file, but don't run it")
             .arg(flag_optimize.clone())
+            .arg(flag_max_threads.clone())
             .arg(flag_opt_size.clone())
             .arg(flag_dev.clone())
             .arg(flag_debug.clone())
@@ -132,6 +151,7 @@ pub fn build_app<'a>() -> Command<'a> {
             .arg(
                 Arg::new(ROC_FILE)
                     .help("The .roc file to build")
+                    .allow_invalid_utf8(true)
                     .required(true),
             )
         )
@@ -141,6 +161,7 @@ pub fn build_app<'a>() -> Command<'a> {
         .subcommand(Command::new(CMD_RUN)
             .about("Run a .roc file even if it has build errors")
             .arg(flag_optimize.clone())
+            .arg(flag_max_threads.clone())
             .arg(flag_opt_size.clone())
             .arg(flag_dev.clone())
             .arg(flag_debug.clone())
@@ -148,11 +169,8 @@ pub fn build_app<'a>() -> Command<'a> {
             .arg(flag_linker.clone())
             .arg(flag_precompiled.clone())
             .arg(flag_valgrind.clone())
-            .arg(
+            .arg(roc_file_to_run.clone().required(true))
-                Arg::new(ROC_FILE)
+            .arg(args_for_app.clone())
-                    .help("The .roc file of an app to run")
-                    .required(true),
-            )
         )
         .subcommand(Command::new(CMD_FORMAT)
             .about("Format a .roc file using standard Roc formatting")
@@ -174,9 +192,11 @@ pub fn build_app<'a>() -> Command<'a> {
         .subcommand(Command::new(CMD_CHECK)
             .about("Check the code for problems, but doesn’t build or run it")
             .arg(flag_time.clone())
+            .arg(flag_max_threads.clone())
             .arg(
                 Arg::new(ROC_FILE)
                     .help("The .roc file of an app to check")
+                    .allow_invalid_utf8(true)
                     .required(true),
             )
             )
@@ -193,6 +213,7 @@ pub fn build_app<'a>() -> Command<'a> {
         )
         .trailing_var_arg(true)
         .arg(flag_optimize)
+            .arg(flag_max_threads.clone())
         .arg(flag_opt_size)
         .arg(flag_dev)
         .arg(flag_debug)
@@ -200,17 +221,8 @@ pub fn build_app<'a>() -> Command<'a> {
         .arg(flag_linker)
         .arg(flag_precompiled)
         .arg(flag_valgrind)
-        .arg(
+        .arg(roc_file_to_run.required(false))
-            Arg::new(ROC_FILE)
+        .arg(args_for_app);
-                .help("The .roc file of an app to build and run")
-                .required(false),
-        )
-        .arg(
-            Arg::new(ARGS_FOR_APP)
-                .help("Arguments to pass into the app being run")
-                .requires(ROC_FILE)
-                .multiple_values(true),
-        );
 
     if cfg!(feature = "editor") {
         app.subcommand(
@@ -236,8 +248,8 @@ pub fn docs(files: Vec<PathBuf>) {
 #[derive(Debug, PartialEq, Eq)]
 pub enum BuildConfig {
     BuildOnly,
-    BuildAndRun { roc_file_arg_index: usize },
+    BuildAndRun,
-    BuildAndRunIfNoErrors { roc_file_arg_index: usize },
+    BuildAndRunIfNoErrors,
 }
 
 pub enum FormatMode {
@@ -255,7 +267,7 @@ pub fn build(
     use BuildConfig::*;
 
     let arena = Bump::new();
-    let filename = matches.value_of(ROC_FILE).unwrap();
+    let filename = matches.value_of_os(ROC_FILE).unwrap();
 
     let original_cwd = std::env::current_dir()?;
     let opt_level = match (
@@ -272,6 +284,16 @@ pub fn build(
     let emit_debug_info = matches.is_present(FLAG_DEBUG);
     let emit_timings = matches.is_present(FLAG_TIME);
 
+    let threading = match matches
+        .value_of(FLAG_MAX_THREADS)
+        .and_then(|s| s.parse::<usize>().ok())
+    {
+        None => Threading::AllAvailable,
+        Some(0) => user_error!("cannot build with at most 0 threads"),
+        Some(1) => Threading::Single,
+        Some(n) => Threading::AtMost(n),
+    };
+
     // Use surgical linking when supported, or when explicitly requested with --linker surgical
     let surgically_link = if matches.is_present(FLAG_LINKER) {
         matches.value_of(FLAG_LINKER) == Some("surgical")
@@ -321,7 +343,7 @@ pub fn build(
         surgically_link,
         precompiled,
         target_valgrind,
-        Threading::Multi,
+        threading,
     );
 
     match res_binary_path {
@@ -372,7 +394,7 @@ pub fn build(
                     // Return a nonzero exit code if there were problems
                     Ok(problems.exit_code())
                 }
-                BuildAndRun { roc_file_arg_index } => {
+                BuildAndRun => {
                     if problems.errors > 0 || problems.warnings > 0 {
                         println!(
                             "\x1B[{}m{}\x1B[39m {} and \x1B[{}m{}\x1B[39m {} found in {} ms.\n\nRunning program anyway…\n\n\x1B[36m{}\x1B[39m",
@@ -403,15 +425,11 @@ pub fn build(
                         );
                     }
 
-                    roc_run(
+                    let args = matches.values_of_os(ARGS_FOR_APP).unwrap_or_default();
-                        arena,
+
-                        &original_cwd,
+                    roc_run(arena, &original_cwd, triple, args, &binary_path)
-                        triple,
-                        roc_file_arg_index,
-                        &binary_path,
-                    )
                 }
-                BuildAndRunIfNoErrors { roc_file_arg_index } => {
+                BuildAndRunIfNoErrors => {
                     if problems.errors == 0 {
                         if problems.warnings > 0 {
                             println!(
@@ -427,13 +445,9 @@ pub fn build(
                             );
                         }
 
-                        roc_run(
+                        let args = matches.values_of_os(ARGS_FOR_APP).unwrap_or_default();
-                            arena,
+
-                            &original_cwd,
+                        roc_run(arena, &original_cwd, triple, args, &binary_path)
-                            triple,
-                            roc_file_arg_index,
-                            &binary_path,
-                        )
                     } else {
                         println!(
                             "\x1B[{}m{}\x1B[39m {} and \x1B[{}m{}\x1B[39m {} found in {} ms.\n\nYou can run the program anyway with: \x1B[32mroc run {}\x1B[39m",
@@ -460,7 +474,7 @@ pub fn build(
                                 "warnings"
                             },
                             total_time.as_millis(),
-                            filename
+                            filename.to_string_lossy()
                         );
 
                         Ok(problems.exit_code())
@@ -479,17 +493,14 @@ pub fn build(
     }
 }
 
-#[cfg(target_family = "unix")]
+fn roc_run<'a, I: IntoIterator<Item = &'a OsStr>>(
-fn roc_run(
     arena: Bump, // This should be passed an owned value, not a reference, so we can usefully mem::forget it!
     cwd: &Path,
     triple: Triple,
-    roc_file_arg_index: usize,
+    args: I,
     binary_path: &Path,
 ) -> io::Result<i32> {
-    use std::os::unix::process::CommandExt;
+    match triple.architecture {
-
-    let mut cmd = match triple.architecture {
         Architecture::Wasm32 => {
             // If possible, report the generated executable name relative to the current dir.
             let generated_filename = binary_path
@@ -500,19 +511,44 @@ fn roc_run(
             // since the process is about to exit anyway.
             std::mem::forget(arena);
 
-            let args = std::env::args()
+            if cfg!(target_family = "unix") {
-                .skip(roc_file_arg_index)
+                use std::os::unix::ffi::OsStrExt;
-                .collect::<Vec<_>>();
 
-            run_with_wasmer(generated_filename, &args);
+                run_with_wasmer(
-            return Ok(0);
+                    generated_filename,
+                    args.into_iter().map(|os_str| os_str.as_bytes()),
+                );
+            } else {
+                run_with_wasmer(
+                    generated_filename,
+                    args.into_iter().map(|os_str| {
+                        os_str.to_str().expect(
+                            "Roc does not currently support passing non-UTF8 arguments to Wasmer.",
+                        )
+                    }),
+                );
             }
-        _ => std::process::Command::new(&binary_path),
-    };
 
-    if let Architecture::Wasm32 = triple.architecture {
+            Ok(0)
-        cmd.arg(binary_path);
         }
+        _ => {
+            if cfg!(target_family = "unix") {
+                roc_run_unix(cwd, args, binary_path)
+            } else {
+                roc_run_non_unix(arena, cwd, args, binary_path)
+            }
+        }
+    }
+}
+
+fn roc_run_unix<I: IntoIterator<Item = S>, S: AsRef<OsStr>>(
+    cwd: &Path,
+    args: I,
+    binary_path: &Path,
+) -> io::Result<i32> {
+    use std::os::unix::process::CommandExt;
+
+    let mut cmd = std::process::Command::new(&binary_path);
 
     // Forward all the arguments after the .roc file argument
     // to the new process. This way, you can do things like:
@@ -521,11 +557,9 @@ fn roc_run(
     //
     // ...and have it so that app.roc will receive only `foo`,
     // `bar`, and `baz` as its arguments.
-    for (index, arg) in std::env::args().enumerate() {
+    for arg in args {
-        if index > roc_file_arg_index {
         cmd.arg(arg);
     }
-    }
 
     // This is much faster than spawning a subprocess if we're on a UNIX system!
     let err = cmd.current_dir(cwd).exec();
@@ -536,29 +570,36 @@ fn roc_run(
     Err(err)
 }
 
-#[cfg(not(target_family = "unix"))]
+fn roc_run_non_unix<I: IntoIterator<Item = S>, S: AsRef<OsStr>>(
-fn roc_run(cmd: &mut Command) -> io::Result<i32> {
+    _arena: Bump, // This should be passed an owned value, not a reference, so we can usefully mem::forget it!
-    // Run the compiled app
+    _cwd: &Path,
-    let exit_status = cmd
+    _args: I,
-                        .spawn()
+    _binary_path: &Path,
-                        .unwrap_or_else(|err| panic!("Failed to run app after building it: {:?}", err))
+) -> io::Result<i32> {
-                        .wait()
+    todo!("TODO support running roc programs on non-UNIX targets");
-                        .expect("TODO gracefully handle block_on failing when `roc` spawns a subprocess for the compiled app");
+    // let mut cmd = std::process::Command::new(&binary_path);
 
-    // `roc [FILE]` exits with the same status code as the app it ran.
+    // // Run the compiled app
-    //
+    // let exit_status = cmd
-    // If you want to know whether there were compilation problems
+    //     .spawn()
-    // via status code, use either `roc build` or `roc check` instead!
+    //     .unwrap_or_else(|err| panic!("Failed to run app after building it: {:?}", err))
-    match exit_status.code() {
+    //     .wait()
-        Some(code) => Ok(code),
+    //     .expect("TODO gracefully handle block_on failing when `roc` spawns a subprocess for the compiled app");
-        None => {
+
-            todo!("TODO gracefully handle the `roc [FILE]` subprocess terminating with a signal.");
+    // // `roc [FILE]` exits with the same status code as the app it ran.
-        }
+    // //
-    }
+    // // If you want to know whether there were compilation problems
+    // // via status code, use either `roc build` or `roc check` instead!
+    // match exit_status.code() {
+    //     Some(code) => Ok(code),
+    //     None => {
+    //         todo!("TODO gracefully handle the `roc [FILE]` subprocess terminating with a signal.");
+    //     }
+    // }
 }
 
 #[cfg(feature = "run-wasm32")]
-fn run_with_wasmer(wasm_path: &std::path::Path, args: &[String]) {
+fn run_with_wasmer<I: Iterator<Item = S>, S: AsRef<[u8]>>(wasm_path: &std::path::Path, args: I) {
     use wasmer::{Instance, Module, Store};
 
     let store = Store::default();
@@ -589,8 +630,8 @@ fn run_with_wasmer(wasm_path: &std::path::Path, args: &[String]) {
 }
 
 #[cfg(not(feature = "run-wasm32"))]
-fn run_with_wasmer(_wasm_path: &std::path::Path, _args: &[String]) {
+fn run_with_wasmer<I: Iterator<Item = S>, S: AsRef<[u8]>>(_wasm_path: &std::path::Path, _args: I) {
-    println!("Running wasm files not support");
+    println!("Running wasm files is not supported on this target.");
 }
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]

cli/src/main.rs

@@ -6,7 +6,7 @@ use roc_cli::{
     FLAG_NO_LINK, FLAG_TARGET, FLAG_TIME, ROC_FILE,
 };
 use roc_error_macros::user_error;
-use roc_load::LoadingProblem;
+use roc_load::{LoadingProblem, Threading};
 use std::fs::{self, FileType};
 use std::io;
 use std::path::{Path, PathBuf};
@@ -27,45 +27,33 @@ fn main() -> io::Result<()> {
 
     let exit_code = match matches.subcommand() {
         None => {
-            match matches.index_of(ROC_FILE) {
+            if matches.is_present(ROC_FILE) {
-                Some(arg_index) => {
-                    let roc_file_arg_index = arg_index + 1; // Not sure why this +1 is necessary, but it is!
-
                 build(
                     &matches,
-                        BuildConfig::BuildAndRunIfNoErrors { roc_file_arg_index },
+                    BuildConfig::BuildAndRunIfNoErrors,
                     Triple::host(),
                     LinkType::Executable,
                 )
-                }
+            } else {
-
-                None => {
                 launch_editor(None)?;
 
                 Ok(0)
             }
         }
-        }
         Some((CMD_RUN, matches)) => {
-            match matches.index_of(ROC_FILE) {
+            if matches.is_present(ROC_FILE) {
-                Some(arg_index) => {
-                    let roc_file_arg_index = arg_index + 1; // Not sure why this +1 is necessary, but it is!
-
                 build(
                     matches,
-                        BuildConfig::BuildAndRun { roc_file_arg_index },
+                    BuildConfig::BuildAndRun,
                     Triple::host(),
                     LinkType::Executable,
                 )
-                }
+            } else {
-
-                None => {
                 eprintln!("What .roc file do you want to run? Specify it at the end of the `roc run` command.");
 
                 Ok(1)
             }
         }
-        }
         Some((CMD_BUILD, matches)) => {
             let target: Target = matches.value_of_t(FLAG_TARGET).unwrap_or_default();
 
@@ -90,11 +78,21 @@ fn main() -> io::Result<()> {
             let arena = bumpalo::Bump::new();
 
             let emit_timings = matches.is_present(FLAG_TIME);
-            let filename = matches.value_of(ROC_FILE).unwrap();
+            let filename = matches.value_of_os(ROC_FILE).unwrap();
             let roc_file_path = PathBuf::from(filename);
             let src_dir = roc_file_path.parent().unwrap().to_owned();
 
-            match check_file(&arena, src_dir, roc_file_path, emit_timings) {
+            let threading = match matches
+                .value_of(roc_cli::FLAG_MAX_THREADS)
+                .and_then(|s| s.parse::<usize>().ok())
+            {
+                None => Threading::AllAvailable,
+                Some(0) => user_error!("cannot build with at most 0 threads"),
+                Some(1) => Threading::Single,
+                Some(n) => Threading::AtMost(n),
+            };
+
+            match check_file(&arena, src_dir, roc_file_path, emit_timings, threading) {
                 Ok((problems, total_time)) => {
                     println!(
                         "\x1B[{}m{}\x1B[39m {} and \x1B[{}m{}\x1B[39m {} found in {} ms.",

cli/tests/cli_run.rs

@@ -14,10 +14,29 @@ mod cli_run {
         known_bad_file, run_cmd, run_roc, run_with_valgrind, Out, ValgrindError,
         ValgrindErrorXWhat,
     };
+    use const_format::concatcp;
     use indoc::indoc;
+    use roc_cli::{CMD_BUILD, CMD_CHECK, CMD_FORMAT, CMD_RUN};
     use roc_test_utils::assert_multiline_str_eq;
     use serial_test::serial;
+    use std::iter;
     use std::path::{Path, PathBuf};
+    use strum::IntoEnumIterator;
+    use strum_macros::EnumIter;
+
+    const OPTIMIZE_FLAG: &str = concatcp!("--", roc_cli::FLAG_OPTIMIZE);
+    const VALGRIND_FLAG: &str = concatcp!("--", roc_cli::FLAG_VALGRIND);
+    const LINKER_FLAG: &str = concatcp!("--", roc_cli::FLAG_LINKER);
+    const CHECK_FLAG: &str = concatcp!("--", roc_cli::FLAG_CHECK);
+    #[allow(dead_code)]
+    const TARGET_FLAG: &str = concatcp!("--", roc_cli::FLAG_TARGET);
+
+    #[derive(Debug, EnumIter)]
+    enum CliMode {
+        RocBuild,
+        RocRun,
+        Roc,
+    }
 
     #[cfg(not(debug_assertions))]
     use roc_collections::all::MutMap;
@@ -65,7 +84,7 @@ mod cli_run {
     }
 
     fn check_compile_error(file: &Path, flags: &[&str], expected: &str) {
-        let compile_out = run_roc(&[&["check", file.to_str().unwrap()], flags].concat());
+        let compile_out = run_roc([CMD_CHECK, file.to_str().unwrap()].iter().chain(flags), &[]);
         let err = compile_out.stdout.trim();
         let err = strip_colors(err);
 
@@ -77,19 +96,41 @@ mod cli_run {
     }
 
     fn check_format_check_as_expected(file: &Path, expects_success_exit_code: bool) {
-        let flags = &["--check"];
+        let out = run_roc([CMD_FORMAT, file.to_str().unwrap(), CHECK_FLAG], &[]);
-        let out = run_roc(&[&["format", file.to_str().unwrap()], &flags[..]].concat());
+
-        if expects_success_exit_code {
+        assert_eq!(out.status.success(), expects_success_exit_code);
-            assert!(out.status.success());
-        } else {
-            assert!(!out.status.success());
-        }
     }
 
-    fn build_example(file: &Path, flags: &[&str]) -> Out {
+    fn run_roc_on<'a, I: IntoIterator<Item = &'a str>>(
-        let compile_out = run_roc(&[&["build", file.to_str().unwrap()], flags].concat());
+        file: &'a Path,
-        if !compile_out.stderr.is_empty() {
+        args: I,
-            panic!("roc build had stderr: {}", compile_out.stderr);
+        stdin: &[&str],
+        input_file: Option<PathBuf>,
+    ) -> Out {
+        let compile_out = match input_file {
+            Some(input_file) => run_roc(
+                // converting these all to String avoids lifetime issues
+                args.into_iter().map(|arg| arg.to_string()).chain([
+                    file.to_str().unwrap().to_string(),
+                    input_file.to_str().unwrap().to_string(),
+                ]),
+                stdin,
+            ),
+            None => run_roc(
+                args.into_iter().chain(iter::once(file.to_str().unwrap())),
+                stdin,
+            ),
+        };
+
+        if !compile_out.stderr.is_empty() &&
+            // If there is any stderr, it should be reporting the runtime and that's it!
+            !(compile_out.stderr.starts_with("runtime: ")
+                && compile_out.stderr.ends_with("ms\n"))
+        {
+            panic!(
+                "`roc` command had unexpected stderr: {}",
+                compile_out.stderr
+            );
         }
 
         assert!(compile_out.status.success(), "bad status {:?}", compile_out);
@@ -106,27 +147,33 @@ mod cli_run {
         expected_ending: &str,
         use_valgrind: bool,
     ) {
-        let mut all_flags = vec![];
+        for cli_mode in CliMode::iter() {
-        all_flags.extend_from_slice(flags);
+            let flags = {
+                let mut vec = flags.to_vec();
 
                 if use_valgrind {
-            all_flags.extend_from_slice(&["--valgrind"]);
+                    vec.push(VALGRIND_FLAG);
                 }
 
-        build_example(file, &all_flags[..]);
+                vec.into_iter()
+            };
 
-        let out = if use_valgrind && ALLOW_VALGRIND {
+            let out = match cli_mode {
-            let (valgrind_out, raw_xml) = if let Some(input_file) = input_file {
+                CliMode::RocBuild => {
+                    run_roc_on(file, iter::once(CMD_BUILD).chain(flags.clone()), &[], None);
+
+                    if use_valgrind && ALLOW_VALGRIND {
+                        let (valgrind_out, raw_xml) = if let Some(ref input_file) = input_file {
                             run_with_valgrind(
-                    stdin,
+                                stdin.clone().iter().copied(),
                                 &[
                                     file.with_file_name(executable_filename).to_str().unwrap(),
-                        input_file.to_str().unwrap(),
+                                    input_file.clone().to_str().unwrap(),
                                 ],
                             )
                         } else {
                             run_with_valgrind(
-                    stdin,
+                                stdin.clone().iter().copied(),
                                 &[file.with_file_name(executable_filename).to_str().unwrap()],
                             )
                         };
@@ -166,27 +213,39 @@ mod cli_run {
                         }
 
                         valgrind_out
-        } else if let Some(input_file) = input_file {
+                    } else if let Some(ref input_file) = input_file {
                         run_cmd(
                             file.with_file_name(executable_filename).to_str().unwrap(),
-                stdin,
+                            stdin.iter().copied(),
                             &[input_file.to_str().unwrap()],
                         )
                     } else {
                         run_cmd(
                             file.with_file_name(executable_filename).to_str().unwrap(),
-                stdin,
+                            stdin.iter().copied(),
                             &[],
                         )
+                    }
+                }
+                CliMode::Roc => run_roc_on(file, flags.clone(), stdin, input_file.clone()),
+                CliMode::RocRun => run_roc_on(
+                    file,
+                    iter::once(CMD_RUN).chain(flags.clone()),
+                    stdin,
+                    input_file.clone(),
+                ),
             };
+
             if !&out.stdout.ends_with(expected_ending) {
                 panic!(
                     "expected output to end with {:?} but instead got {:#?} - stderr was: {:#?}",
                     expected_ending, out.stdout, out.stderr
                 );
             }
+
             assert!(out.status.success());
         }
+    }
 
     #[cfg(feature = "wasm32-cli-run")]
     fn check_wasm_output_with_stdin(
@@ -199,9 +258,13 @@ mod cli_run {
     ) {
         assert_eq!(input_file, None, "Wasm does not support input files");
         let mut flags = flags.to_vec();
-        flags.push("--target=wasm32");
+        flags.push(concatcp!(TARGET_FLAG, "=wasm32"));
 
-        let compile_out = run_roc(&[&["build", file.to_str().unwrap()], flags.as_slice()].concat());
+        let compile_out = run_roc(
+            [CMD_BUILD, file.to_str().unwrap()]
+                .iter()
+                .chain(flags.as_slice()),
+        );
         if !compile_out.stderr.is_empty() {
             panic!("{}", compile_out.stderr);
         }
@@ -258,7 +321,7 @@ mod cli_run {
                         }
                         "hello-gui" | "breakout" => {
                             // Since these require opening a window, we do `roc build` on them but don't run them.
-                            build_example(&file_name, &["--optimize"]);
+                            run_roc_on(&file_name, [CMD_BUILD, OPTIMIZE_FLAG], &[], None);
 
                             return;
                         }
@@ -283,7 +346,7 @@ mod cli_run {
                         &file_name,
                         example.stdin,
                         example.executable_filename,
-                        &["--optimize"],
+                        &[OPTIMIZE_FLAG],
                         example.input_file.and_then(|file| Some(example_file(dir_name, file))),
                         example.expected_ending,
                         example.use_valgrind,
@@ -296,7 +359,7 @@ mod cli_run {
                             &file_name,
                             example.stdin,
                             example.executable_filename,
-                            &["--linker", "legacy"],
+                            &[LINKER_FLAG, "legacy"],
                             example.input_file.and_then(|file| Some(example_file(dir_name, file))),
                             example.expected_ending,
                             example.use_valgrind,
@@ -513,7 +576,7 @@ mod cli_run {
                         &file_name,
                         benchmark.stdin,
                         benchmark.executable_filename,
-                        &["--optimize"],
+                        &[OPTIMIZE_FLAG],
                         benchmark.input_file.and_then(|file| Some(examples_dir("benchmarks").join(file))),
                         benchmark.expected_ending,
                         benchmark.use_valgrind,
@@ -555,7 +618,7 @@ mod cli_run {
                         &file_name,
                         benchmark.stdin,
                         benchmark.executable_filename,
-                        &["--optimize"],
+                        &[OPTIMIZE_FLAG],
                         benchmark.input_file.and_then(|file| Some(examples_dir("benchmarks").join(file))),
                         benchmark.expected_ending,
                     );
@@ -587,7 +650,7 @@ mod cli_run {
                         &file_name,
                         benchmark.stdin,
                         benchmark.executable_filename,
-                        &["--target=x86_32"],
+                        [concatcp!(TARGET_FLAG, "=x86_32")],
                         benchmark.input_file.and_then(|file| Some(examples_dir("benchmarks").join(file))),
                         benchmark.expected_ending,
                         benchmark.use_valgrind,
@@ -597,7 +660,7 @@ mod cli_run {
                         &file_name,
                         benchmark.stdin,
                         benchmark.executable_filename,
-                        &["--target=x86_32", "--optimize"],
+                        [concatcp!(TARGET_FLAG, "=x86_32"), OPTIMIZE_FLAG],
                         benchmark.input_file.and_then(|file| Some(examples_dir("benchmarks").join(file))),
                         benchmark.expected_ending,
                         benchmark.use_valgrind,
@@ -816,7 +879,7 @@ mod cli_run {
             &fixture_file("multi-dep-str", "Main.roc"),
             &[],
             "multi-dep-str",
-            &["--optimize"],
+            &[OPTIMIZE_FLAG],
             None,
             "I am Dep2.str2\n",
             true,
@@ -844,7 +907,7 @@ mod cli_run {
             &fixture_file("multi-dep-thunk", "Main.roc"),
             &[],
             "multi-dep-thunk",
-            &["--optimize"],
+            &[OPTIMIZE_FLAG],
             None,
             "I am Dep2.value2\n",
             true,

cli_utils/Cargo.toml

@@ -20,6 +20,7 @@ serde = { version = "1.0.130", features = ["derive"] }
 serde-xml-rs = "0.5.1"
 strip-ansi-escapes = "0.1.1"
 tempfile = "3.2.0"
+const_format = "0.2.22"
 
 [target.'cfg(unix)'.dependencies]
 rlimit = "0.6.2"

cli_utils/src/bench_utils.rs

@@ -1,9 +1,13 @@
 use crate::helpers::{example_file, run_cmd, run_roc};
+use const_format::concatcp;
 use criterion::{black_box, measurement::Measurement, BenchmarkGroup};
+use roc_cli::CMD_BUILD;
 use std::{path::Path, thread};
 
 const CFOLD_STACK_SIZE: usize = 8192 * 100000;
 
+const OPTIMIZE_FLAG: &str = concatcp!("--", roc_cli::FLAG_OPTIMIZE);
+
 fn exec_bench_w_input<T: Measurement>(
     file: &Path,
     stdin_str: &'static str,
@@ -11,9 +15,10 @@ fn exec_bench_w_input<T: Measurement>(
     expected_ending: &str,
     bench_group_opt: Option<&mut BenchmarkGroup<T>>,
 ) {
-    let flags: &[&str] = &["--optimize"];
+    let compile_out = run_roc(
-
+        [CMD_BUILD, OPTIMIZE_FLAG, file.to_str().unwrap()],
-    let compile_out = run_roc(&[&["build", file.to_str().unwrap()], flags].concat());
+        &[stdin_str],
+    );
 
     if !compile_out.stderr.is_empty() {
         panic!("{}", compile_out.stderr);
@@ -45,12 +50,12 @@ fn check_cmd_output(
     let out = if cmd_str.contains("cfold") {
         let child = thread::Builder::new()
             .stack_size(CFOLD_STACK_SIZE)
-            .spawn(move || run_cmd(&cmd_str, &[stdin_str], &[]))
+            .spawn(move || run_cmd(&cmd_str, [stdin_str], &[]))
             .unwrap();
 
         child.join().unwrap()
     } else {
-        run_cmd(&cmd_str, &[stdin_str], &[])
+        run_cmd(&cmd_str, [stdin_str], &[])
     };
 
     if !&out.stdout.ends_with(expected_ending) {
@@ -93,12 +98,12 @@ fn bench_cmd<T: Measurement>(
 
     if let Some(bench_group) = bench_group_opt {
         bench_group.bench_function(&format!("Benchmarking {:?}", executable_filename), |b| {
-            b.iter(|| run_cmd(black_box(&cmd_str), black_box(&[stdin_str]), &[]))
+            b.iter(|| run_cmd(black_box(&cmd_str), black_box([stdin_str]), &[]))
         });
     } else {
         run_cmd(
             black_box(file.with_file_name(executable_filename).to_str().unwrap()),
-            black_box(&[stdin_str]),
+            black_box([stdin_str]),
             &[],
         );
     }

cli_utils/src/helpers.rs

@@ -7,6 +7,7 @@ extern crate tempfile;
 use serde::Deserialize;
 use serde_xml_rs::from_str;
 use std::env;
+use std::ffi::OsStr;
 use std::io::Read;
 use std::io::Write;
 use std::path::PathBuf;
@@ -44,18 +45,34 @@ pub fn path_to_roc_binary() -> PathBuf {
     path
 }
 
-#[allow(dead_code)]
+pub fn run_roc<I: IntoIterator<Item = S>, S: AsRef<OsStr>>(args: I, stdin_vals: &[&str]) -> Out {
-pub fn run_roc(args: &[&str]) -> Out {
     let mut cmd = Command::new(path_to_roc_binary());
 
     for arg in args {
         cmd.arg(arg);
     }
 
-    let output = cmd
+    let mut child = cmd
-        .output()
+        .stdin(Stdio::piped())
+        .stdout(Stdio::piped())
+        .stderr(Stdio::piped())
+        .spawn()
         .expect("failed to execute compiled `roc` binary in CLI test");
 
+    {
+        let stdin = child.stdin.as_mut().expect("Failed to open stdin");
+
+        for stdin_str in stdin_vals.iter() {
+            stdin
+                .write_all(stdin_str.as_bytes())
+                .expect("Failed to write to stdin");
+        }
+    }
+
+    let output = child
+        .wait_with_output()
+        .expect("failed to get output for compiled `roc` binary in CLI test");
+
     Out {
         stdout: String::from_utf8(output.stdout).unwrap(),
         stderr: String::from_utf8(output.stderr).unwrap(),
@@ -63,8 +80,11 @@ pub fn run_roc(args: &[&str]) -> Out {
     }
 }
 
-#[allow(dead_code)]
+pub fn run_cmd<'a, I: IntoIterator<Item = &'a str>>(
-pub fn run_cmd(cmd_name: &str, stdin_vals: &[&str], args: &[&str]) -> Out {
+    cmd_name: &str,
+    stdin_vals: I,
+    args: &[&str],
+) -> Out {
     let mut cmd = Command::new(cmd_name);
 
     for arg in args {
@@ -99,8 +119,10 @@ pub fn run_cmd(cmd_name: &str, stdin_vals: &[&str], args: &[&str]) -> Out {
     }
 }
 
-#[allow(dead_code)]
+pub fn run_with_valgrind<'a, I: IntoIterator<Item = &'a str>>(
-pub fn run_with_valgrind(stdin_vals: &[&str], args: &[&str]) -> (Out, String) {
+    stdin_vals: I,
+    args: &[&str],
+) -> (Out, String) {
     //TODO: figure out if there is a better way to get the valgrind executable.
     let mut cmd = Command::new("valgrind");
     let named_tempfile =

compiler/builtins/bitcode/src/main.zig

@@ -106,6 +106,9 @@ comptime {
             num.exportToIntCheckingMax(FROM, TO, ROC_BUILTINS ++ "." ++ NUM ++ ".int_to_" ++ @typeName(TO) ++ "_checking_max.");
             num.exportToIntCheckingMaxAndMin(FROM, TO, ROC_BUILTINS ++ "." ++ NUM ++ ".int_to_" ++ @typeName(TO) ++ "_checking_max_and_min.");
         }
+
+        num.exportRoundF32(FROM, ROC_BUILTINS ++ "." ++ NUM ++ ".round_f32.");
+        num.exportRoundF64(FROM, ROC_BUILTINS ++ "." ++ NUM ++ ".round_f64.");
     }
 
     inline for (FLOATS) |T| {
@@ -114,7 +117,6 @@ comptime {
         num.exportAtan(T, ROC_BUILTINS ++ "." ++ NUM ++ ".atan.");
 
         num.exportIsFinite(T, ROC_BUILTINS ++ "." ++ NUM ++ ".is_finite.");
-        num.exportRound(T, ROC_BUILTINS ++ "." ++ NUM ++ ".round.");
     }
 }
 

compiler/builtins/bitcode/src/num.zig

@@ -90,10 +90,19 @@ pub fn exportAtan(comptime T: type, comptime name: []const u8) void {
     @export(f, .{ .name = name ++ @typeName(T), .linkage = .Strong });
 }
 
-pub fn exportRound(comptime T: type, comptime name: []const u8) void {
+pub fn exportRoundF32(comptime T: type, comptime name: []const u8) void {
     comptime var f = struct {
-        fn func(input: T) callconv(.C) i64 {
+        fn func(input: f32) callconv(.C) T {
-            return @floatToInt(i64, (@round(input)));
+            return @floatToInt(T, (@round(input)));
+        }
+    }.func;
+    @export(f, .{ .name = name ++ @typeName(T), .linkage = .Strong });
+}
+
+pub fn exportRoundF64(comptime T: type, comptime name: []const u8) void {
+    comptime var f = struct {
+        fn func(input: f64) callconv(.C) T {
+            return @floatToInt(T, (@round(input)));
         }
     }.func;
     @export(f, .{ .name = name ++ @typeName(T), .linkage = .Strong });

compiler/builtins/src/bitcode.rs

@@ -279,7 +279,9 @@ pub const NUM_ATAN: IntrinsicName = float_intrinsic!("roc_builtins.num.atan");
 pub const NUM_IS_FINITE: IntrinsicName = float_intrinsic!("roc_builtins.num.is_finite");
 pub const NUM_POW_INT: IntrinsicName = int_intrinsic!("roc_builtins.num.pow_int");
 pub const NUM_DIV_CEIL: IntrinsicName = int_intrinsic!("roc_builtins.num.div_ceil");
-pub const NUM_ROUND: IntrinsicName = float_intrinsic!("roc_builtins.num.round");
+
+pub const NUM_ROUND_F32: IntrinsicName = int_intrinsic!("roc_builtins.num.round_f32");
+pub const NUM_ROUND_F64: IntrinsicName = int_intrinsic!("roc_builtins.num.round_f64");
 
 pub const NUM_BYTES_TO_U16: &str = "roc_builtins.num.bytes_to_u16";
 pub const NUM_BYTES_TO_U32: &str = "roc_builtins.num.bytes_to_u32";

compiler/can/Cargo.toml

@@ -14,8 +14,6 @@ roc_module = { path = "../module" }
 roc_parse = { path = "../parse" }
 roc_problem = { path = "../problem" }
 roc_types = { path = "../types" }
-roc_builtins = { path = "../builtins" }
-ven_graph = { path = "../../vendor/pathfinding" }
 bumpalo = { version = "3.8.0", features = ["collections"] }
 static_assertions = "1.1.0"
 bitvec = "1"

compiler/can/src/def.rs

@@ -192,17 +192,12 @@ fn sort_type_defs_before_introduction(
     }
 
     // find the strongly connected components and their relations
-    let nodes: Vec<_> = (0..capacity as u32).collect();
+    matrix
-
+        .strongly_connected_components_all()
-    let mut output = Vec::with_capacity(capacity);
+        .groups()
-
+        .flat_map(|group| group.iter_ones())
-    for group in matrix.strongly_connected_components(&nodes).groups() {
+        .map(|index| symbols[index])
-        for index in group.iter_ones() {
+        .collect()
-            output.push(symbols[index])
-        }
-    }
-
-    output
 }
 
 #[inline(always)]
@@ -790,14 +785,10 @@ pub(crate) fn sort_can_defs(
         };
     }
 
-    let nodes: Vec<_> = (0..defs.len() as u32).collect();
-
     // We first perform SCC based on any reference, both variable usage and calls
     // considering both value definitions and function bodies. This will spot any
     // recursive relations between any 2 definitions.
-    let sccs = def_ordering
+    let sccs = def_ordering.references.strongly_connected_components_all();
-        .references
-        .strongly_connected_components(&nodes);
 
     let mut declarations = Vec::new();
 
@@ -838,10 +829,9 @@ pub(crate) fn sort_can_defs(
             // boom = \{} -> boom {}
             //
             // In general we cannot spot faulty recursion (halting problem) so this is our best attempt
-            let nodes: Vec<_> = group.iter_ones().map(|v| v as u32).collect();
             let direct_sccs = def_ordering
                 .direct_references
-                .strongly_connected_components(&nodes);
+                .strongly_connected_components_subset(group);
 
             let declaration = if direct_sccs.groups().count() == 1 {
                 // all defs are part of the same direct cycle, that is invalid!
@@ -1571,8 +1561,7 @@ fn correct_mutual_recursive_type_alias<'a>(
 
     let mut solved_aliases = bitvec::vec::BitVec::<usize>::repeat(false, capacity);
 
-    let group: Vec<_> = (0u32..capacity as u32).collect();
+    let sccs = matrix.strongly_connected_components_all();
-    let sccs = matrix.strongly_connected_components(&group);
 
     // scratchpad to store aliases that are modified in the current iteration.
     // Only used when there is are more than one alias in a group. See below why

compiler/can/src/reference_matrix.rs

@@ -129,8 +129,14 @@ impl ReferenceMatrix {
         TopologicalSort::Groups { groups }
     }
 
-    /// Get the strongly-connected components of the set of input nodes.
+    /// Get the strongly-connected components all nodes in the matrix
-    pub fn strongly_connected_components(&self, nodes: &[u32]) -> Sccs {
+    pub fn strongly_connected_components_all(&self) -> Sccs {
+        let bitvec = BitVec::repeat(true, self.length);
+        self.strongly_connected_components_subset(&bitvec)
+    }
+
+    /// Get the strongly-connected components of a set of input nodes.
+    pub fn strongly_connected_components_subset(&self, nodes: &BitSlice) -> Sccs {
         let mut params = Params::new(self.length, nodes);
 
         'outer: loop {
@@ -176,15 +182,15 @@ struct Params {
     p: Vec<u32>,
     s: Vec<u32>,
     scc: Sccs,
-    scca: Vec<u32>,
+    scca: BitVec,
 }
 
 impl Params {
-    fn new(length: usize, group: &[u32]) -> Self {
+    fn new(length: usize, group: &BitSlice) -> Self {
         let mut preorders = vec![Preorder::Removed; length];
 
-        for value in group {
+        for index in group.iter_ones() {
-            preorders[*value as usize] = Preorder::Empty;
+            preorders[index] = Preorder::Empty;
         }
 
         Self {
@@ -196,7 +202,7 @@ impl Params {
                 matrix: ReferenceMatrix::new(length),
                 components: 0,
             },
-            scca: Vec::new(),
+            scca: BitVec::repeat(false, length),
         }
     }
 }
@@ -210,7 +216,7 @@ fn recurse_onto(length: usize, bitvec: &BitVec, v: usize, params: &mut Params) {
     params.p.push(v as u32);
 
     for w in bitvec[v * length..][..length].iter_ones() {
-        if !params.scca.contains(&(w as u32)) {
+        if !params.scca[w] {
             match params.preorders[w] {
                 Preorder::Filled(pw) => loop {
                     let index = *params.p.last().unwrap();
@@ -241,7 +247,7 @@ fn recurse_onto(length: usize, bitvec: &BitVec, v: usize, params: &mut Params) {
                 .scc
                 .matrix
                 .set_row_col(params.scc.components, node as usize, true);
-            params.scca.push(node);
+            params.scca.set(node as usize, true);
             params.preorders[node as usize] = Preorder::Removed;
             if node as usize == v {
                 break;

compiler/collections/src/vec_map.rs

@@ -13,6 +13,13 @@ impl<K, V> Default for VecMap<K, V> {
     }
 }
 
+impl<K, V> VecMap<K, V> {
+    pub fn len(&self) -> usize {
+        debug_assert_eq!(self.keys.len(), self.values.len());
+        self.keys.len()
+    }
+}
+
 impl<K: PartialEq, V> VecMap<K, V> {
     pub fn with_capacity(capacity: usize) -> Self {
         Self {
@@ -21,11 +28,6 @@ impl<K: PartialEq, V> VecMap<K, V> {
         }
     }
 
-    pub fn len(&self) -> usize {
-        debug_assert_eq!(self.keys.len(), self.values.len());
-        self.keys.len()
-    }
-
     pub fn is_empty(&self) -> bool {
         debug_assert_eq!(self.keys.len(), self.values.len());
         self.keys.is_empty()
@@ -58,15 +60,9 @@ impl<K: PartialEq, V> VecMap<K, V> {
         self.keys.contains(key)
     }
 
-    pub fn remove(&mut self, key: &K) {
+    pub fn remove(&mut self, key: &K) -> Option<(K, V)> {
-        match self.keys.iter().position(|x| x == key) {
+        let index = self.keys.iter().position(|x| x == key)?;
-            None => {
+        Some(self.swap_remove(index))
-                // just do nothing
-            }
-            Some(index) => {
-                self.swap_remove(index);
-            }
-        }
     }
 
     pub fn get(&self, key: &K) -> Option<&V> {
@@ -83,7 +79,7 @@ impl<K: PartialEq, V> VecMap<K, V> {
         }
     }
 
-    pub fn get_or_insert(&mut self, key: K, default_value: impl Fn() -> V) -> &mut V {
+    pub fn get_or_insert(&mut self, key: K, default_value: impl FnOnce() -> V) -> &mut V {
         match self.keys.iter().position(|x| x == &key) {
             Some(index) => &mut self.values[index],
             None => {
@@ -97,15 +93,15 @@ impl<K: PartialEq, V> VecMap<K, V> {
         }
     }
 
-    pub fn iter(&self) -> impl Iterator<Item = (&K, &V)> {
+    pub fn iter(&self) -> impl ExactSizeIterator<Item = (&K, &V)> {
         self.keys.iter().zip(self.values.iter())
     }
 
-    pub fn keys(&self) -> impl Iterator<Item = &K> {
+    pub fn keys(&self) -> impl ExactSizeIterator<Item = &K> {
         self.keys.iter()
     }
 
-    pub fn values(&self) -> impl Iterator<Item = &V> {
+    pub fn values(&self) -> impl ExactSizeIterator<Item = &V> {
         self.values.iter()
     }
 
@@ -159,6 +155,7 @@ impl<K, V> IntoIterator for VecMap<K, V> {
 
     fn into_iter(self) -> Self::IntoIter {
         IntoIter {
+            len: self.len(),
             keys: self.keys.into_iter(),
             values: self.values.into_iter(),
         }
@@ -166,6 +163,7 @@ impl<K, V> IntoIterator for VecMap<K, V> {
 }
 
 pub struct IntoIter<K, V> {
+    len: usize,
     keys: std::vec::IntoIter<K>,
     values: std::vec::IntoIter<V>,
 }
@@ -180,3 +178,9 @@ impl<K, V> Iterator for IntoIter<K, V> {
         }
     }
 }
+
+impl<K, V> ExactSizeIterator for IntoIter<K, V> {
+    fn len(&self) -> usize {
+        self.len
+    }
+}

compiler/fmt/src/lib.rs

@@ -10,6 +10,14 @@ pub mod pattern;
 pub mod spaces;
 
 use bumpalo::{collections::String, Bump};
+use roc_parse::ast::{Def, Module};
+use roc_region::all::Loc;
+
+#[derive(Debug, PartialEq)]
+pub struct Ast<'a> {
+    pub module: Module<'a>,
+    pub defs: bumpalo::collections::vec::Vec<'a, Loc<Def<'a>>>,
+}
 
 #[derive(Debug)]
 pub struct Buf<'a> {

compiler/fmt/src/spaces.rs

@@ -1,6 +1,21 @@
-use roc_parse::ast::CommentOrNewline;
+use bumpalo::collections::vec::Vec;
+use bumpalo::Bump;
+use roc_module::called_via::{BinOp, UnaryOp};
+use roc_parse::{
+    ast::{
+        AbilityMember, AssignedField, Collection, CommentOrNewline, Def, Expr, Has, HasClause,
+        Module, Pattern, Spaced, StrLiteral, StrSegment, Tag, TypeAnnotation, TypeDef, TypeHeader,
+        ValueDef, WhenBranch,
+    },
+    header::{
+        AppHeader, ExposedName, HostedHeader, ImportsEntry, InterfaceHeader, ModuleName,
+        PackageEntry, PackageName, PlatformHeader, PlatformRequires, To, TypedIdent,
+    },
+    ident::UppercaseIdent,
+};
+use roc_region::all::{Loc, Region};
 
-use crate::Buf;
+use crate::{Ast, Buf};
 
 /// The number of spaces to indent.
 pub const INDENT: u16 = 4;
@@ -149,3 +164,575 @@ fn fmt_docs<'buf>(buf: &mut Buf<'buf>, docs: &str) {
     }
     buf.push_str(docs);
 }
+
+/// RemoveSpaces normalizes the ast to something that we _expect_ to be invariant under formatting.
+///
+/// Currently this consists of:
+/// * Removing newlines
+/// * Removing comments
+/// * Removing parens in Exprs
+///
+/// Long term, we actuall want this transform to preserve comments (so we can assert they're maintained by formatting)
+/// - but there are currently several bugs where they're _not_ preserved.
+/// TODO: ensure formatting retains comments
+pub trait RemoveSpaces<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self;
+}
+
+impl<'a> RemoveSpaces<'a> for Ast<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        Ast {
+            module: self.module.remove_spaces(arena),
+            defs: {
+                let mut defs = Vec::with_capacity_in(self.defs.len(), arena);
+                for d in &self.defs {
+                    defs.push(d.remove_spaces(arena))
+                }
+                defs
+            },
+        }
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for Module<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        match self {
+            Module::Interface { header } => Module::Interface {
+                header: InterfaceHeader {
+                    name: header.name.remove_spaces(arena),
+                    exposes: header.exposes.remove_spaces(arena),
+                    imports: header.imports.remove_spaces(arena),
+                    before_header: &[],
+                    after_interface_keyword: &[],
+                    before_exposes: &[],
+                    after_exposes: &[],
+                    before_imports: &[],
+                    after_imports: &[],
+                },
+            },
+            Module::App { header } => Module::App {
+                header: AppHeader {
+                    name: header.name.remove_spaces(arena),
+                    packages: header.packages.remove_spaces(arena),
+                    imports: header.imports.remove_spaces(arena),
+                    provides: header.provides.remove_spaces(arena),
+                    provides_types: header.provides_types.map(|ts| ts.remove_spaces(arena)),
+                    to: header.to.remove_spaces(arena),
+                    before_header: &[],
+                    after_app_keyword: &[],
+                    before_packages: &[],
+                    after_packages: &[],
+                    before_imports: &[],
+                    after_imports: &[],
+                    before_provides: &[],
+                    after_provides: &[],
+                    before_to: &[],
+                    after_to: &[],
+                },
+            },
+            Module::Platform { header } => Module::Platform {
+                header: PlatformHeader {
+                    name: header.name.remove_spaces(arena),
+                    requires: header.requires.remove_spaces(arena),
+                    exposes: header.exposes.remove_spaces(arena),
+                    packages: header.packages.remove_spaces(arena),
+                    imports: header.imports.remove_spaces(arena),
+                    provides: header.provides.remove_spaces(arena),
+                    before_header: &[],
+                    after_platform_keyword: &[],
+                    before_requires: &[],
+                    after_requires: &[],
+                    before_exposes: &[],
+                    after_exposes: &[],
+                    before_packages: &[],
+                    after_packages: &[],
+                    before_imports: &[],
+                    after_imports: &[],
+                    before_provides: &[],
+                    after_provides: &[],
+                },
+            },
+            Module::Hosted { header } => Module::Hosted {
+                header: HostedHeader {
+                    name: header.name.remove_spaces(arena),
+                    exposes: header.exposes.remove_spaces(arena),
+                    imports: header.imports.remove_spaces(arena),
+                    generates: header.generates.remove_spaces(arena),
+                    generates_with: header.generates_with.remove_spaces(arena),
+                    before_header: &[],
+                    after_hosted_keyword: &[],
+                    before_exposes: &[],
+                    after_exposes: &[],
+                    before_imports: &[],
+                    after_imports: &[],
+                    before_generates: &[],
+                    after_generates: &[],
+                    before_with: &[],
+                    after_with: &[],
+                },
+            },
+        }
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for &'a str {
+    fn remove_spaces(&self, _arena: &'a Bump) -> Self {
+        self
+    }
+}
+
+impl<'a, T: RemoveSpaces<'a> + Copy> RemoveSpaces<'a> for Spaced<'a, T> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        match *self {
+            Spaced::Item(a) => Spaced::Item(a.remove_spaces(arena)),
+            Spaced::SpaceBefore(a, _) => a.remove_spaces(arena),
+            Spaced::SpaceAfter(a, _) => a.remove_spaces(arena),
+        }
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for ExposedName<'a> {
+    fn remove_spaces(&self, _arena: &'a Bump) -> Self {
+        *self
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for ModuleName<'a> {
+    fn remove_spaces(&self, _arena: &'a Bump) -> Self {
+        *self
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for PackageName<'a> {
+    fn remove_spaces(&self, _arena: &'a Bump) -> Self {
+        *self
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for To<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        match *self {
+            To::ExistingPackage(a) => To::ExistingPackage(a),
+            To::NewPackage(a) => To::NewPackage(a.remove_spaces(arena)),
+        }
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for TypedIdent<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        TypedIdent {
+            ident: self.ident.remove_spaces(arena),
+            spaces_before_colon: &[],
+            ann: self.ann.remove_spaces(arena),
+        }
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for PlatformRequires<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        PlatformRequires {
+            rigids: self.rigids.remove_spaces(arena),
+            signature: self.signature.remove_spaces(arena),
+        }
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for UppercaseIdent<'a> {
+    fn remove_spaces(&self, _arena: &'a Bump) -> Self {
+        *self
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for PackageEntry<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        PackageEntry {
+            shorthand: self.shorthand,
+            spaces_after_shorthand: &[],
+            package_name: self.package_name.remove_spaces(arena),
+        }
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for ImportsEntry<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        match *self {
+            ImportsEntry::Module(a, b) => ImportsEntry::Module(a, b.remove_spaces(arena)),
+            ImportsEntry::Package(a, b, c) => ImportsEntry::Package(a, b, c.remove_spaces(arena)),
+        }
+    }
+}
+
+impl<'a, T: RemoveSpaces<'a>> RemoveSpaces<'a> for Option<T> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        self.as_ref().map(|a| a.remove_spaces(arena))
+    }
+}
+
+impl<'a, T: RemoveSpaces<'a> + std::fmt::Debug> RemoveSpaces<'a> for Loc<T> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        let res = self.value.remove_spaces(arena);
+        Loc::at(Region::zero(), res)
+    }
+}
+
+impl<'a, A: RemoveSpaces<'a>, B: RemoveSpaces<'a>> RemoveSpaces<'a> for (A, B) {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        (self.0.remove_spaces(arena), self.1.remove_spaces(arena))
+    }
+}
+
+impl<'a, T: RemoveSpaces<'a>> RemoveSpaces<'a> for Collection<'a, T> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        let mut items = Vec::with_capacity_in(self.items.len(), arena);
+        for item in self.items {
+            items.push(item.remove_spaces(arena));
+        }
+        Collection::with_items(items.into_bump_slice())
+    }
+}
+
+impl<'a, T: RemoveSpaces<'a> + std::fmt::Debug> RemoveSpaces<'a> for &'a [T] {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        let mut items = Vec::with_capacity_in(self.len(), arena);
+        for item in *self {
+            let res = item.remove_spaces(arena);
+            items.push(res);
+        }
+        items.into_bump_slice()
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for UnaryOp {
+    fn remove_spaces(&self, _arena: &'a Bump) -> Self {
+        *self
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for BinOp {
+    fn remove_spaces(&self, _arena: &'a Bump) -> Self {
+        *self
+    }
+}
+
+impl<'a, T: RemoveSpaces<'a>> RemoveSpaces<'a> for &'a T {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        arena.alloc((*self).remove_spaces(arena))
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for TypeDef<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        use TypeDef::*;
+
+        match *self {
+            Alias {
+                header: TypeHeader { name, vars },
+                ann,
+            } => Alias {
+                header: TypeHeader {
+                    name: name.remove_spaces(arena),
+                    vars: vars.remove_spaces(arena),
+                },
+                ann: ann.remove_spaces(arena),
+            },
+            Opaque {
+                header: TypeHeader { name, vars },
+                typ,
+            } => Opaque {
+                header: TypeHeader {
+                    name: name.remove_spaces(arena),
+                    vars: vars.remove_spaces(arena),
+                },
+                typ: typ.remove_spaces(arena),
+            },
+            Ability {
+                header: TypeHeader { name, vars },
+                loc_has,
+                members,
+            } => Ability {
+                header: TypeHeader {
+                    name: name.remove_spaces(arena),
+                    vars: vars.remove_spaces(arena),
+                },
+                loc_has: loc_has.remove_spaces(arena),
+                members: members.remove_spaces(arena),
+            },
+        }
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for ValueDef<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        use ValueDef::*;
+
+        match *self {
+            Annotation(a, b) => Annotation(a.remove_spaces(arena), b.remove_spaces(arena)),
+            Body(a, b) => Body(
+                arena.alloc(a.remove_spaces(arena)),
+                arena.alloc(b.remove_spaces(arena)),
+            ),
+            AnnotatedBody {
+                ann_pattern,
+                ann_type,
+                comment: _,
+                body_pattern,
+                body_expr,
+            } => AnnotatedBody {
+                ann_pattern: arena.alloc(ann_pattern.remove_spaces(arena)),
+                ann_type: arena.alloc(ann_type.remove_spaces(arena)),
+                comment: None,
+                body_pattern: arena.alloc(body_pattern.remove_spaces(arena)),
+                body_expr: arena.alloc(body_expr.remove_spaces(arena)),
+            },
+            Expect(a) => Expect(arena.alloc(a.remove_spaces(arena))),
+        }
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for Def<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        match *self {
+            Def::Type(def) => Def::Type(def.remove_spaces(arena)),
+            Def::Value(def) => Def::Value(def.remove_spaces(arena)),
+            Def::NotYetImplemented(a) => Def::NotYetImplemented(a),
+            Def::SpaceBefore(a, _) | Def::SpaceAfter(a, _) => a.remove_spaces(arena),
+        }
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for Has<'a> {
+    fn remove_spaces(&self, _arena: &'a Bump) -> Self {
+        Has::Has
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for AbilityMember<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        AbilityMember {
+            name: self.name.remove_spaces(arena),
+            typ: self.typ.remove_spaces(arena),
+        }
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for WhenBranch<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        WhenBranch {
+            patterns: self.patterns.remove_spaces(arena),
+            value: self.value.remove_spaces(arena),
+            guard: self.guard.remove_spaces(arena),
+        }
+    }
+}
+
+impl<'a, T: RemoveSpaces<'a> + Copy + std::fmt::Debug> RemoveSpaces<'a> for AssignedField<'a, T> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        match *self {
+            AssignedField::RequiredValue(a, _, c) => AssignedField::RequiredValue(
+                a.remove_spaces(arena),
+                arena.alloc([]),
+                arena.alloc(c.remove_spaces(arena)),
+            ),
+            AssignedField::OptionalValue(a, _, c) => AssignedField::OptionalValue(
+                a.remove_spaces(arena),
+                arena.alloc([]),
+                arena.alloc(c.remove_spaces(arena)),
+            ),
+            AssignedField::LabelOnly(a) => AssignedField::LabelOnly(a.remove_spaces(arena)),
+            AssignedField::Malformed(a) => AssignedField::Malformed(a),
+            AssignedField::SpaceBefore(a, _) => a.remove_spaces(arena),
+            AssignedField::SpaceAfter(a, _) => a.remove_spaces(arena),
+        }
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for StrLiteral<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        match *self {
+            StrLiteral::PlainLine(t) => StrLiteral::PlainLine(t),
+            StrLiteral::Line(t) => StrLiteral::Line(t.remove_spaces(arena)),
+            StrLiteral::Block(t) => StrLiteral::Block(t.remove_spaces(arena)),
+        }
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for StrSegment<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        match *self {
+            StrSegment::Plaintext(t) => StrSegment::Plaintext(t),
+            StrSegment::Unicode(t) => StrSegment::Unicode(t.remove_spaces(arena)),
+            StrSegment::EscapedChar(c) => StrSegment::EscapedChar(c),
+            StrSegment::Interpolated(t) => StrSegment::Interpolated(t.remove_spaces(arena)),
+        }
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for Expr<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        match *self {
+            Expr::Float(a) => Expr::Float(a),
+            Expr::Num(a) => Expr::Num(a),
+            Expr::NonBase10Int {
+                string,
+                base,
+                is_negative,
+            } => Expr::NonBase10Int {
+                string,
+                base,
+                is_negative,
+            },
+            Expr::Str(a) => Expr::Str(a.remove_spaces(arena)),
+            Expr::Access(a, b) => Expr::Access(arena.alloc(a.remove_spaces(arena)), b),
+            Expr::AccessorFunction(a) => Expr::AccessorFunction(a),
+            Expr::List(a) => Expr::List(a.remove_spaces(arena)),
+            Expr::RecordUpdate { update, fields } => Expr::RecordUpdate {
+                update: arena.alloc(update.remove_spaces(arena)),
+                fields: fields.remove_spaces(arena),
+            },
+            Expr::Record(a) => Expr::Record(a.remove_spaces(arena)),
+            Expr::Var { module_name, ident } => Expr::Var { module_name, ident },
+            Expr::Underscore(a) => Expr::Underscore(a),
+            Expr::Tag(a) => Expr::Tag(a),
+            Expr::OpaqueRef(a) => Expr::OpaqueRef(a),
+            Expr::Closure(a, b) => Expr::Closure(
+                arena.alloc(a.remove_spaces(arena)),
+                arena.alloc(b.remove_spaces(arena)),
+            ),
+            Expr::Defs(a, b) => {
+                Expr::Defs(a.remove_spaces(arena), arena.alloc(b.remove_spaces(arena)))
+            }
+            Expr::Backpassing(a, b, c) => Expr::Backpassing(
+                arena.alloc(a.remove_spaces(arena)),
+                arena.alloc(b.remove_spaces(arena)),
+                arena.alloc(c.remove_spaces(arena)),
+            ),
+            Expr::Expect(a, b) => Expr::Expect(
+                arena.alloc(a.remove_spaces(arena)),
+                arena.alloc(b.remove_spaces(arena)),
+            ),
+            Expr::Apply(a, b, c) => Expr::Apply(
+                arena.alloc(a.remove_spaces(arena)),
+                b.remove_spaces(arena),
+                c,
+            ),
+            Expr::BinOps(a, b) => {
+                Expr::BinOps(a.remove_spaces(arena), arena.alloc(b.remove_spaces(arena)))
+            }
+            Expr::UnaryOp(a, b) => {
+                Expr::UnaryOp(arena.alloc(a.remove_spaces(arena)), b.remove_spaces(arena))
+            }
+            Expr::If(a, b) => Expr::If(a.remove_spaces(arena), arena.alloc(b.remove_spaces(arena))),
+            Expr::When(a, b) => {
+                Expr::When(arena.alloc(a.remove_spaces(arena)), b.remove_spaces(arena))
+            }
+            Expr::ParensAround(a) => {
+                // The formatter can remove redundant parentheses, so also remove these when normalizing for comparison.
+                a.remove_spaces(arena)
+            }
+            Expr::MalformedIdent(a, b) => Expr::MalformedIdent(a, b),
+            Expr::MalformedClosure => Expr::MalformedClosure,
+            Expr::PrecedenceConflict(a) => Expr::PrecedenceConflict(a),
+            Expr::SpaceBefore(a, _) => a.remove_spaces(arena),
+            Expr::SpaceAfter(a, _) => a.remove_spaces(arena),
+            Expr::SingleQuote(a) => Expr::Num(a),
+        }
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for Pattern<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        match *self {
+            Pattern::Identifier(a) => Pattern::Identifier(a),
+            Pattern::Tag(a) => Pattern::Tag(a),
+            Pattern::OpaqueRef(a) => Pattern::OpaqueRef(a),
+            Pattern::Apply(a, b) => Pattern::Apply(
+                arena.alloc(a.remove_spaces(arena)),
+                arena.alloc(b.remove_spaces(arena)),
+            ),
+            Pattern::RecordDestructure(a) => Pattern::RecordDestructure(a.remove_spaces(arena)),
+            Pattern::RequiredField(a, b) => {
+                Pattern::RequiredField(a, arena.alloc(b.remove_spaces(arena)))
+            }
+            Pattern::OptionalField(a, b) => {
+                Pattern::OptionalField(a, arena.alloc(b.remove_spaces(arena)))
+            }
+            Pattern::NumLiteral(a) => Pattern::NumLiteral(a),
+            Pattern::NonBase10Literal {
+                string,
+                base,
+                is_negative,
+            } => Pattern::NonBase10Literal {
+                string,
+                base,
+                is_negative,
+            },
+            Pattern::FloatLiteral(a) => Pattern::FloatLiteral(a),
+            Pattern::StrLiteral(a) => Pattern::StrLiteral(a),
+            Pattern::Underscore(a) => Pattern::Underscore(a),
+            Pattern::Malformed(a) => Pattern::Malformed(a),
+            Pattern::MalformedIdent(a, b) => Pattern::MalformedIdent(a, b),
+            Pattern::QualifiedIdentifier { module_name, ident } => {
+                Pattern::QualifiedIdentifier { module_name, ident }
+            }
+            Pattern::SpaceBefore(a, _) => a.remove_spaces(arena),
+            Pattern::SpaceAfter(a, _) => a.remove_spaces(arena),
+            Pattern::SingleQuote(a) => Pattern::NumLiteral(a),
+        }
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for TypeAnnotation<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        match *self {
+            TypeAnnotation::Function(a, b) => TypeAnnotation::Function(
+                arena.alloc(a.remove_spaces(arena)),
+                arena.alloc(b.remove_spaces(arena)),
+            ),
+            TypeAnnotation::Apply(a, b, c) => TypeAnnotation::Apply(a, b, c.remove_spaces(arena)),
+            TypeAnnotation::BoundVariable(a) => TypeAnnotation::BoundVariable(a),
+            TypeAnnotation::As(a, _, c) => {
+                TypeAnnotation::As(arena.alloc(a.remove_spaces(arena)), &[], c)
+            }
+            TypeAnnotation::Record { fields, ext } => TypeAnnotation::Record {
+                fields: fields.remove_spaces(arena),
+                ext: ext.remove_spaces(arena),
+            },
+            TypeAnnotation::TagUnion { ext, tags } => TypeAnnotation::TagUnion {
+                ext: ext.remove_spaces(arena),
+                tags: tags.remove_spaces(arena),
+            },
+            TypeAnnotation::Inferred => TypeAnnotation::Inferred,
+            TypeAnnotation::Wildcard => TypeAnnotation::Wildcard,
+            TypeAnnotation::Where(annot, has_clauses) => TypeAnnotation::Where(
+                arena.alloc(annot.remove_spaces(arena)),
+                arena.alloc(has_clauses.remove_spaces(arena)),
+            ),
+            TypeAnnotation::SpaceBefore(a, _) => a.remove_spaces(arena),
+            TypeAnnotation::SpaceAfter(a, _) => a.remove_spaces(arena),
+            TypeAnnotation::Malformed(a) => TypeAnnotation::Malformed(a),
+        }
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for HasClause<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        HasClause {
+            var: self.var.remove_spaces(arena),
+            ability: self.ability.remove_spaces(arena),
+        }
+    }
+}
+
+impl<'a> RemoveSpaces<'a> for Tag<'a> {
+    fn remove_spaces(&self, arena: &'a Bump) -> Self {
+        match *self {
+            Tag::Apply { name, args } => Tag::Apply {
+                name: name.remove_spaces(arena),
+                args: args.remove_spaces(arena),
+            },
+            Tag::Malformed(a) => Tag::Malformed(a),
+            Tag::SpaceBefore(a, _) => a.remove_spaces(arena),
+            Tag::SpaceAfter(a, _) => a.remove_spaces(arena),
+        }
+    }
+}

compiler/fmt/tests/test_fmt.rs

@@ -10,60 +10,153 @@ mod test_fmt {
     use roc_fmt::def::fmt_def;
     use roc_fmt::module::fmt_module;
     use roc_fmt::Buf;
+    use roc_parse::ast::Module;
     use roc_parse::module::{self, module_defs};
     use roc_parse::parser::Parser;
     use roc_parse::state::State;
     use roc_test_utils::assert_multiline_str_eq;
 
     // Not intended to be used directly in tests; please use expr_formats_to or expr_formats_same
-    fn expect_format_expr_helper(input: &str, expected: &str) {
+    fn expr_formats_to(input: &str, expected: &str) {
         let arena = Bump::new();
-        match roc_parse::test_helpers::parse_expr_with(&arena, input.trim()) {
+        let input = input.trim();
+        let expected = expected.trim();
+
+        match roc_parse::test_helpers::parse_expr_with(&arena, input) {
             Ok(actual) => {
+                use roc_fmt::spaces::RemoveSpaces;
+
                 let mut buf = Buf::new_in(&arena);
 
                 actual.format_with_options(&mut buf, Parens::NotNeeded, Newlines::Yes, 0);
 
-                assert_multiline_str_eq!(expected, buf.as_str());
+                let output = buf.as_str();
+
+                assert_multiline_str_eq!(expected, output);
+
+                let reparsed_ast = roc_parse::test_helpers::parse_expr_with(&arena, output).unwrap_or_else(|err| {
+                    panic!(
+                        "After formatting, the source code no longer parsed!\n\nParse error was: {:?}\n\nThe code that failed to parse:\n\n{}\n\n",
+                        err, output
+                    );
+                });
+
+                let ast_normalized = actual.remove_spaces(&arena);
+                let reparsed_ast_normalized = reparsed_ast.remove_spaces(&arena);
+
+                // HACK!
+                // We compare the debug format strings of the ASTs, because I'm finding in practice that _somewhere_ deep inside the ast,
+                // the PartialEq implementation is returning `false` even when the Debug-formatted impl is exactly the same.
+                // I don't have the patience to debug this right now, so let's leave it for another day...
+                // TODO: fix PartialEq impl on ast types
+                if format!("{:?}", ast_normalized) != format!("{:?}", reparsed_ast_normalized) {
+                    panic!(
+                        "Formatting bug; formatting didn't reparse to the same AST (after removing spaces)\n\n\
+                        * * * Source code before formatting:\n{}\n\n\
+                        * * * Source code after formatting:\n{}\n\n",
+                        input,
+                        output
+                    );
+                }
+
+                // Now verify that the resultant formatting is _stable_ - i.e. that it doesn't change again if re-formatted
+                let mut reformatted_buf = Buf::new_in(&arena);
+                reparsed_ast.format_with_options(&mut reformatted_buf, Parens::NotNeeded, Newlines::Yes, 0);
+
+                if output != reformatted_buf.as_str() {
+                    eprintln!("Formatting bug; formatting is not stable. Reformatting the formatted code changed it again, as follows:\n\n");
+
+                    assert_multiline_str_eq!(output, reformatted_buf.as_str());
+                }
             }
             Err(error) => panic!("Unexpected parse failure when parsing this for formatting:\n\n{}\n\nParse error was:\n\n{:?}\n\n", input, error)
         };
     }
 
-    fn expr_formats_to(input: &str, expected: &str) {
-        let input = input.trim_end();
-        let expected = expected.trim_end();
-
-        // First check that input formats to the expected version
-        expect_format_expr_helper(input, expected);
-
-        // Parse the expected result format it, asserting that it doesn't change
-        // It's important that formatting be stable / idempotent
-        expect_format_expr_helper(expected, expected);
-    }
-
     fn expr_formats_same(input: &str) {
         expr_formats_to(input, input);
     }
 
-    // Not intended to be used directly in tests; please use module_formats_to or module_formats_same
+    fn fmt_module_and_defs<'a>(
-    fn expect_format_module_helper(src: &str, expected: &str) {
+        arena: &Bump,
-        let arena = Bump::new();
+        src: &str,
-        match module::parse_header(&arena, State::new(src.as_bytes())) {
+        module: &Module<'a>,
-            Ok((actual, state)) => {
+        state: State<'a>,
-                let mut buf = Buf::new_in(&arena);
+        buf: &mut Buf<'_>,
-
+    ) {
-                fmt_module(&mut buf, &actual);
+        fmt_module(buf, module);
 
         match module_defs().parse(&arena, state) {
             Ok((_, loc_defs, _)) => {
                 for loc_def in loc_defs {
-                            fmt_def(&mut buf, arena.alloc(loc_def.value), 0);
+                    fmt_def(buf, arena.alloc(loc_def.value), 0);
                 }
             }
             Err(error) => panic!("Unexpected parse failure when parsing this for defs formatting:\n\n{:?}\n\nParse error was:\n\n{:?}\n\n", src, error)
         }
-                assert_multiline_str_eq!(expected, buf.as_str())
+    }
+
+    // Not intended to be used directly in tests; please use module_formats_to or module_formats_same
+    fn expect_format_module_helper(src: &str, expected: &str) {
+        let arena = Bump::new();
+        let src = src.trim();
+        let expected = expected.trim();
+
+        match module::parse_header(&arena, State::new(src.as_bytes())) {
+            Ok((actual, state)) => {
+                use roc_fmt::spaces::RemoveSpaces;
+
+                let mut buf = Buf::new_in(&arena);
+
+                fmt_module_and_defs(&arena, src, &actual, state, &mut buf);
+
+                let output = buf.as_str().trim();
+
+                let (reparsed_ast, state) = module::parse_header(&arena, State::new(output.as_bytes())).unwrap_or_else(|err| {
+                    panic!(
+                        "After formatting, the source code no longer parsed!\n\nParse error was: {:?}\n\nThe code that failed to parse:\n\n{}\n\n",
+                        err, output
+                    );
+                });
+
+                let ast_normalized = actual.remove_spaces(&arena);
+                let reparsed_ast_normalized = reparsed_ast.remove_spaces(&arena);
+
+                // HACK!
+                // We compare the debug format strings of the ASTs, because I'm finding in practice that _somewhere_ deep inside the ast,
+                // the PartialEq implementation is returning `false` even when the Debug-formatted impl is exactly the same.
+                // I don't have the patience to debug this right now, so let's leave it for another day...
+                // TODO: fix PartialEq impl on ast types
+                if format!("{:?}", ast_normalized) != format!("{:?}", reparsed_ast_normalized) {
+                    panic!(
+                        "Formatting bug; formatting didn't reparse to the same AST (after removing spaces)\n\n\
+                        * * * Source code before formatting:\n{}\n\n\
+                        * * * Source code after formatting:\n{}\n\n",
+                        src,
+                        output
+                    );
+                }
+
+                // Now verify that the resultant formatting is _stable_ - i.e. that it doesn't change again if re-formatted
+                let mut reformatted_buf = Buf::new_in(&arena);
+
+                fmt_module_and_defs(&arena, output, &reparsed_ast, state, &mut reformatted_buf);
+
+                let reformatted = reformatted_buf.as_str().trim();
+
+                if output != reformatted {
+                    eprintln!("Formatting bug; formatting is not stable. Reformatting the formatted code changed it again, as follows:\n\n");
+
+                    assert_multiline_str_eq!(output, reformatted);
+                }
+
+                // If everything was idempotent re-parsing worked, finally assert
+                // that the formatted code was what we expected it to be.
+                //
+                // Do this last because if there were any serious problems with the
+                // formatter (e.g. it wasn't idempotent), we want to know about
+                // those more than we want to know that the expectation failed!
+                assert_multiline_str_eq!(expected, output);
             }
             Err(error) => panic!("Unexpected parse failure when parsing this for module header formatting:\n\n{:?}\n\nParse error was:\n\n{:?}\n\n", src, error)
         };
@@ -3939,6 +4032,39 @@ mod test_fmt {
         );
     }
 
+    #[test]
+    fn format_tui_package_config() {
+        // At one point this failed to reformat.
+        module_formats_to(
+            indoc!(
+                r#"
+                    platform "tui"
+                        requires { Model } { main : { init : ({} -> Model), update : (Model, Str -> Model), view : (Model -> Str) } }
+                        exposes []
+                        packages {}
+                        imports []
+                        provides [ mainForHost ]
+
+                    mainForHost : { init : ({} -> Model) as Init, update : (Model, Str -> Model) as Update, view : (Model -> Str) as View }
+                    mainForHost = main
+                "#
+            ),
+            indoc!(
+                r#"
+                    platform "tui"
+                        requires { Model } { main : { init : {} -> Model, update : Model, Str -> Model, view : Model -> Str } }
+                        exposes []
+                        packages {}
+                        imports []
+                        provides [ mainForHost ]
+
+                    mainForHost : { init : ({} -> Model) as Init, update : (Model, Str -> Model) as Update, view : (Model -> Str) as View }
+                    mainForHost = main
+                "#
+            ),
+        );
+    }
+
     #[test]
     fn single_line_hosted() {
         module_formats_same(indoc!(

compiler/gen_dev/src/lib.rs

@@ -554,7 +554,7 @@ trait Backend<'a> {
             }
             LowLevel::NumRound => self.build_fn_call(
                 sym,
-                bitcode::NUM_ROUND[FloatWidth::F64].to_string(),
+                bitcode::NUM_ROUND_F64[IntWidth::I64].to_string(),
                 args,
                 arg_layouts,
                 ret_layout,

compiler/gen_llvm/src/llvm/build.rs

@@ -602,6 +602,7 @@ static LLVM_SIN: IntrinsicName = float_intrinsic!("llvm.sin");
 static LLVM_COS: IntrinsicName = float_intrinsic!("llvm.cos");
 static LLVM_CEILING: IntrinsicName = float_intrinsic!("llvm.ceil");
 static LLVM_FLOOR: IntrinsicName = float_intrinsic!("llvm.floor");
+static LLVM_ROUND: IntrinsicName = float_intrinsic!("llvm.round");
 
 static LLVM_MEMSET_I64: &str = "llvm.memset.p0i8.i64";
 static LLVM_MEMSET_I32: &str = "llvm.memset.p0i8.i32";
@@ -7403,20 +7404,67 @@ fn build_float_unary_op<'a, 'ctx, 'env>(
                 }
             }
         }
-        NumCeiling => env.builder.build_cast(
+        NumCeiling => {
-            InstructionOpcode::FPToSI,
+            let (return_signed, return_type) = match layout {
+                Layout::Builtin(Builtin::Int(int_width)) => (
+                    int_width.is_signed(),
+                    convert::int_type_from_int_width(env, *int_width),
+                ),
+                _ => internal_error!("Ceiling return layout is not int: {:?}", layout),
+            };
+            let opcode = if return_signed {
+                InstructionOpcode::FPToSI
+            } else {
+                InstructionOpcode::FPToUI
+            };
+            env.builder.build_cast(
+                opcode,
                 env.call_intrinsic(&LLVM_CEILING[float_width], &[arg.into()]),
-            env.context.i64_type(),
+                return_type,
                 "num_ceiling",
+            )
+        }
+        NumFloor => {
+            let (return_signed, return_type) = match layout {
+                Layout::Builtin(Builtin::Int(int_width)) => (
+                    int_width.is_signed(),
+                    convert::int_type_from_int_width(env, *int_width),
                 ),
-        NumFloor => env.builder.build_cast(
+                _ => internal_error!("Ceiling return layout is not int: {:?}", layout),
-            InstructionOpcode::FPToSI,
+            };
+            let opcode = if return_signed {
+                InstructionOpcode::FPToSI
+            } else {
+                InstructionOpcode::FPToUI
+            };
+            env.builder.build_cast(
+                opcode,
                 env.call_intrinsic(&LLVM_FLOOR[float_width], &[arg.into()]),
-            env.context.i64_type(),
+                return_type,
                 "num_floor",
+            )
+        }
+        NumRound => {
+            let (return_signed, return_type) = match layout {
+                Layout::Builtin(Builtin::Int(int_width)) => (
+                    int_width.is_signed(),
+                    convert::int_type_from_int_width(env, *int_width),
                 ),
+                _ => internal_error!("Ceiling return layout is not int: {:?}", layout),
+            };
+            let opcode = if return_signed {
+                InstructionOpcode::FPToSI
+            } else {
+                InstructionOpcode::FPToUI
+            };
+            env.builder.build_cast(
+                opcode,
+                env.call_intrinsic(&LLVM_ROUND[float_width], &[arg.into()]),
+                return_type,
+                "num_round",
+            )
+        }
         NumIsFinite => call_bitcode_fn(env, &[arg.into()], &bitcode::NUM_IS_FINITE[float_width]),
-        NumRound => call_bitcode_fn(env, &[arg.into()], &bitcode::NUM_ROUND[float_width]),
 
         // trigonometry
         NumSin => env.call_intrinsic(&LLVM_SIN[float_width], &[arg.into()]),

compiler/gen_wasm/src/low_level.rs

@@ -561,18 +561,6 @@ impl<'a> LowLevelCall<'a> {
             NumCos => todo!("{:?}", self.lowlevel),
             NumSqrtUnchecked => todo!("{:?}", self.lowlevel),
             NumLogUnchecked => todo!("{:?}", self.lowlevel),
-            NumRound => {
-                self.load_args(backend);
-                match CodeGenNumType::for_symbol(backend, self.arguments[0]) {
-                    F32 => {
-                        self.load_args_and_call_zig(backend, &bitcode::NUM_ROUND[FloatWidth::F32])
-                    }
-                    F64 => {
-                        self.load_args_and_call_zig(backend, &bitcode::NUM_ROUND[FloatWidth::F64])
-                    }
-                    _ => todo!("{:?} for {:?}", self.lowlevel, self.ret_layout),
-                }
-            }
             NumToFloat => {
                 self.load_args(backend);
                 let ret_type = CodeGenNumType::from(self.ret_layout);
@@ -592,35 +580,54 @@ impl<'a> LowLevelCall<'a> {
                 }
             }
             NumPow => todo!("{:?}", self.lowlevel),
-            NumCeiling => {
+            NumRound => {
                 self.load_args(backend);
-                match CodeGenNumType::from(self.ret_layout) {
+                let arg_type = CodeGenNumType::for_symbol(backend, self.arguments[0]);
-                    I32 => {
+                let ret_type = CodeGenNumType::from(self.ret_layout);
+
+                let width = match ret_type {
+                    CodeGenNumType::I32 => IntWidth::I32,
+                    CodeGenNumType::I64 => IntWidth::I64,
+                    CodeGenNumType::I128 => todo!("{:?} for I128", self.lowlevel),
+                    _ => internal_error!("Invalid return type for round: {:?}", ret_type),
+                };
+
+                match arg_type {
+                    F32 => self.load_args_and_call_zig(backend, &bitcode::NUM_ROUND_F32[width]),
+                    F64 => self.load_args_and_call_zig(backend, &bitcode::NUM_ROUND_F64[width]),
+                    _ => internal_error!("Invalid argument type for round: {:?}", arg_type),
+                }
+            }
+            NumCeiling | NumFloor => {
+                self.load_args(backend);
+                let arg_type = CodeGenNumType::for_symbol(backend, self.arguments[0]);
+                let ret_type = CodeGenNumType::from(self.ret_layout);
+                match (arg_type, self.lowlevel) {
+                    (F32, NumCeiling) => {
                         backend.code_builder.f32_ceil();
-                        backend.code_builder.i32_trunc_s_f32()
                     }
-                    I64 => {
+                    (F64, NumCeiling) => {
                         backend.code_builder.f64_ceil();
-                        backend.code_builder.i64_trunc_s_f64()
                     }
+                    (F32, NumFloor) => {
+                        backend.code_builder.f32_floor();
+                    }
+                    (F64, NumFloor) => {
+                        backend.code_builder.f64_floor();
+                    }
+                    _ => internal_error!("Invalid argument type for ceiling: {:?}", arg_type),
+                }
+                match (ret_type, arg_type) {
+                    // TODO: unsigned truncation
+                    (I32, F32) => backend.code_builder.i32_trunc_s_f32(),
+                    (I32, F64) => backend.code_builder.i32_trunc_s_f64(),
+                    (I64, F32) => backend.code_builder.i64_trunc_s_f32(),
+                    (I64, F64) => backend.code_builder.i64_trunc_s_f64(),
+                    (I128, _) => todo!("{:?} for I128", self.lowlevel),
                     _ => panic_ret_type(),
                 }
             }
             NumPowInt => todo!("{:?}", self.lowlevel),
-            NumFloor => {
-                self.load_args(backend);
-                match CodeGenNumType::from(self.ret_layout) {
-                    I32 => {
-                        backend.code_builder.f32_floor();
-                        backend.code_builder.i32_trunc_s_f32()
-                    }
-                    I64 => {
-                        backend.code_builder.f64_floor();
-                        backend.code_builder.i64_trunc_s_f64()
-                    }
-                    _ => panic_ret_type(),
-                }
-            }
             NumIsFinite => num_is_finite(backend, self.arguments[0]),
 
             NumAtan => match self.ret_layout {

compiler/ident/Cargo.toml

@@ -4,6 +4,3 @@ version = "0.1.0"
 authors = ["The Roc Contributors"]
 license = "UPL-1.0"
 edition = "2018"
-
-[dependencies]
-arrayvec = "0.7.2"

compiler/load/build.rs

@@ -38,7 +38,7 @@ fn write_subs_for_module(module_id: ModuleId, filename: &str) {
         Default::default(),
         target_info,
         roc_reporting::report::RenderTarget::ColorTerminal,
-        Threading::Multi,
+        Threading::AllAvailable,
     );
 
     let module = res_module.unwrap();

compiler/load_internal/Cargo.toml

@@ -22,15 +22,12 @@ roc_mono = { path = "../mono" }
 roc_target = { path = "../roc_target" }
 roc_reporting = { path = "../../reporting" }
 roc_debug_flags = { path = "../debug_flags" }
-morphic_lib = { path = "../../vendor/morphic_lib" }
 ven_pretty = { path = "../../vendor/pretty" }
 bumpalo = { version = "3.8.0", features = ["collections"] }
 parking_lot = "0.12"
 crossbeam = "0.8.1"
-num_cpus = "1.13.0"
 
 [dev-dependencies]
-tempfile = "3.2.0"
 pretty_assertions = "1.0.0"
 maplit = "1.0.2"
 indoc = "1.0.3"

compiler/load_internal/src/file.rs

@@ -747,6 +747,7 @@ impl<'a> State<'a> {
         ident_ids_by_module: SharedIdentIdsByModule,
         cached_subs: MutMap<ModuleId, (Subs, Vec<(Symbol, Variable)>)>,
         render: RenderTarget,
+        number_of_workers: usize,
     ) -> Self {
         let arc_shorthands = Arc::new(Mutex::new(MutMap::default()));
 
@@ -770,7 +771,7 @@ impl<'a> State<'a> {
             declarations_by_id: MutMap::default(),
             exposed_symbols_by_module: MutMap::default(),
             timings: MutMap::default(),
-            layout_caches: std::vec::Vec::with_capacity(num_cpus::get()),
+            layout_caches: std::vec::Vec::with_capacity(number_of_workers),
             cached_subs: Arc::new(Mutex::new(cached_subs)),
             render,
         }
@@ -1099,7 +1100,8 @@ pub enum LoadResult<'a> {
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub enum Threading {
     Single,
-    Multi,
+    AllAvailable,
+    AtMost(usize),
 }
 
 /// The loading process works like this, starting from the given filename (e.g. "main.roc"):
@@ -1157,21 +1159,32 @@ pub fn load<'a>(
     render: RenderTarget,
     threading: Threading,
 ) -> Result<LoadResult<'a>, LoadingProblem<'a>> {
+    enum Threads {
+        Single,
+        Many(usize),
+    }
+
+    let threads = {
+        if cfg!(target_family = "wasm") {
             // When compiling to wasm, we cannot spawn extra threads
             // so we have a single-threaded implementation
-    if threading == Threading::Single || cfg!(target_family = "wasm") {
+            Threads::Single
-        load_single_threaded(
-            arena,
-            load_start,
-            src_dir,
-            exposed_types,
-            goal_phase,
-            target_info,
-            cached_subs,
-            render,
-        )
         } else {
-        load_multi_threaded(
+            match std::thread::available_parallelism().map(|v| v.get()) {
+                Err(_) => Threads::Single,
+                Ok(0) => unreachable!("NonZeroUsize"),
+                Ok(1) => Threads::Single,
+                Ok(reported) => match threading {
+                    Threading::Single => Threads::Single,
+                    Threading::AllAvailable => Threads::Many(reported),
+                    Threading::AtMost(at_most) => Threads::Many(Ord::min(reported, at_most)),
+                },
+            }
+        }
+    };
+
+    match threads {
+        Threads::Single => load_single_threaded(
             arena,
             load_start,
             src_dir,
@@ -1180,7 +1193,18 @@ pub fn load<'a>(
             target_info,
             cached_subs,
             render,
-        )
+        ),
+        Threads::Many(threads) => load_multi_threaded(
+            arena,
+            load_start,
+            src_dir,
+            exposed_types,
+            goal_phase,
+            target_info,
+            cached_subs,
+            render,
+            threads,
+        ),
     }
 }
 
@@ -1210,6 +1234,7 @@ pub fn load_single_threaded<'a>(
         .send(root_msg)
         .map_err(|_| LoadingProblem::MsgChannelDied)?;
 
+    let number_of_workers = 1;
     let mut state = State::new(
         root_id,
         target_info,
@@ -1219,6 +1244,7 @@ pub fn load_single_threaded<'a>(
         ident_ids_by_module,
         cached_subs,
         render,
+        number_of_workers,
     );
 
     // We'll add tasks to this, and then worker threads will take tasks from it.
@@ -1390,6 +1416,7 @@ fn load_multi_threaded<'a>(
     target_info: TargetInfo,
     cached_subs: MutMap<ModuleId, (Subs, Vec<(Symbol, Variable)>)>,
     render: RenderTarget,
+    available_threads: usize,
 ) -> Result<LoadResult<'a>, LoadingProblem<'a>> {
     let LoadStart {
         arc_modules,
@@ -1399,6 +1426,28 @@ fn load_multi_threaded<'a>(
         ..
     } = load_start;
 
+    let (msg_tx, msg_rx) = bounded(1024);
+    msg_tx
+        .send(root_msg)
+        .map_err(|_| LoadingProblem::MsgChannelDied)?;
+
+    // Reserve one CPU for the main thread, and let all the others be eligible
+    // to spawn workers.
+    let available_workers = available_threads - 1;
+
+    let num_workers = match env::var("ROC_NUM_WORKERS") {
+        Ok(env_str) => env_str
+            .parse::<usize>()
+            .unwrap_or(available_workers)
+            .min(available_workers),
+        Err(_) => available_workers,
+    };
+
+    assert!(
+        num_workers >= 1,
+        "`load_multi_threaded` needs at least one worker"
+    );
+
     let mut state = State::new(
         root_id,
         target_info,
@@ -1408,28 +1457,9 @@ fn load_multi_threaded<'a>(
         ident_ids_by_module,
         cached_subs,
         render,
+        num_workers,
     );
 
-    let (msg_tx, msg_rx) = bounded(1024);
-    msg_tx
-        .send(root_msg)
-        .map_err(|_| LoadingProblem::MsgChannelDied)?;
-
-    // Reserve one CPU for the main thread, and let all the others be eligible
-    // to spawn workers. We use .max(2) to enforce that we always
-    // end up with at least 1 worker - since (.max(2) - 1) will
-    // always return a number that's at least 1. Using
-    // .max(2) on the initial number of CPUs instead of
-    // doing .max(1) on the entire expression guards against
-    // num_cpus returning 0, while also avoiding wrapping
-    // unsigned subtraction overflow.
-    let default_num_workers = num_cpus::get().max(2) - 1;
-
-    let num_workers = match env::var("ROC_NUM_WORKERS") {
-        Ok(env_str) => env_str.parse::<usize>().unwrap_or(default_num_workers),
-        Err(_) => default_num_workers,
-    };
-
     // an arena for every worker, stored in an arena-allocated bumpalo vec to make the lifetimes work
     let arenas = std::iter::repeat_with(Bump::new).take(num_workers);
     let worker_arenas = arena.alloc(bumpalo::collections::Vec::from_iter_in(arenas, arena));

compiler/module/Cargo.toml

@@ -14,4 +14,3 @@ bumpalo = { version = "3.8.0", features = ["collections"] }
 lazy_static = "1.4.0"
 static_assertions = "1.1.0"
 snafu = { version = "0.6.10", features = ["backtraces"] }
-arrayvec = "0.7.2"

compiler/mono/Cargo.toml

@@ -21,7 +21,6 @@ roc_target = { path = "../roc_target" }
 roc_error_macros = {path="../../error_macros"}
 roc_debug_flags = {path="../debug_flags"}
 ven_pretty = { path = "../../vendor/pretty" }
-morphic_lib = { path = "../../vendor/morphic_lib" }
 bumpalo = { version = "3.8.0", features = ["collections"] }
 hashbrown = { version = "0.11.2", features = [ "bumpalo" ] }
 ven_graph = { path = "../../vendor/pathfinding" }

compiler/mono/src/decision_tree.rs

@@ -1210,15 +1210,8 @@ pub fn optimize_when<'a>(
         // bind the fields referenced in the pattern. For guards this happens separately, so
         // the pattern variables are defined when evaluating the guard.
         if !has_guard {
-            branch = crate::ir::store_pattern(
+            branch =
-                env,
+                crate::ir::store_pattern(env, procs, layout_cache, &pattern, cond_symbol, branch);
-                procs,
-                layout_cache,
-                &pattern,
-                cond_layout,
-                cond_symbol,
-                branch,
-            );
         }
 
         let ((branch_index, choice), opt_jump) = create_choices(&target_counts, index, branch);
@@ -1730,15 +1723,7 @@ fn decide_to_branching<'a>(
                 body: arena.alloc(decide),
             };
 
-            crate::ir::store_pattern(
+            crate::ir::store_pattern(env, procs, layout_cache, &pattern, cond_symbol, join)
-                env,
-                procs,
-                layout_cache,
-                &pattern,
-                cond_layout,
-                cond_symbol,
-                join,
-            )
         }
         Chain {
             test_chain,

compiler/mono/src/ir.rs

@@ -10,10 +10,12 @@ use roc_builtins::bitcode::{FloatWidth, IntWidth};
 use roc_can::abilities::AbilitiesStore;
 use roc_can::expr::{AnnotatedMark, ClosureData, IntValue};
 use roc_collections::all::{default_hasher, BumpMap, BumpMapDefault, MutMap};
+use roc_collections::VecMap;
 use roc_debug_flags::{
     dbg_do, ROC_PRINT_IR_AFTER_REFCOUNT, ROC_PRINT_IR_AFTER_RESET_REUSE,
     ROC_PRINT_IR_AFTER_SPECIALIZATION,
 };
+use roc_error_macros::internal_error;
 use roc_exhaustive::{Ctor, CtorName, Guard, RenderAs, TagId};
 use roc_module::ident::{ForeignSymbol, Lowercase, TagName};
 use roc_module::low_level::LowLevel;
@@ -743,6 +745,157 @@ impl<'a> Specialized<'a> {
     }
 }
 
+/// Uniquely determines the specialization of a polymorphic (non-proc) value symbol.
+/// Two specializations are equivalent if their [`SpecializationMark`]s are equal.
+#[derive(PartialEq, Eq, Debug, Clone, Copy)]
+struct SpecializationMark<'a> {
+    /// The layout of the symbol itself.
+    layout: Layout<'a>,
+
+    /// If this symbol is a closure def, we must also keep track of what function it specializes,
+    /// because the [`layout`] field will only keep track of its closure and lambda set - which can
+    /// be the same for two different function specializations. For example,
+    ///
+    ///   id = if True then \x -> x else \y -> y
+    ///   { a: id "", b: id 1u8 }
+    ///
+    /// The lambda set and captures of `id` is the same in both usages inside the record, but the
+    /// reified specializations of `\x -> x` and `\y -> y` must be for Str and U8.
+    ///
+    /// Note that this field is not relevant for anything that is not a function.
+    function_mark: Option<RawFunctionLayout<'a>>,
+}
+
+/// When walking a function body, we may encounter specialized usages of polymorphic symbols. For
+/// example
+///
+///  myTag = A
+///  use1 : [A, B]
+///  use1 = myTag
+///  use2 : [A, B, C]
+///  use2 = myTag
+///
+/// We keep track of the specializations of `myTag` and create fresh symbols when there is more
+/// than one, so that a unique def can be created for each.
+#[derive(Default, Debug, Clone)]
+struct SymbolSpecializations<'a>(
+    // THEORY:
+    //  1. the number of symbols in a def is very small
+    //  2. the number of specializations of a symbol in a def is even smaller (almost always only one)
+    // So, a linear VecMap is preferrable. Use a two-layered one to make (1) extraction of defs easy
+    // and (2) reads of a certain symbol be determined by its first occurrence, not its last.
+    VecMap<Symbol, VecMap<SpecializationMark<'a>, (Variable, Symbol)>>,
+);
+
+impl<'a> SymbolSpecializations<'a> {
+    /// Gets a specialization for a symbol, or creates a new one.
+    #[inline(always)]
+    fn get_or_insert(
+        &mut self,
+        env: &mut Env<'a, '_>,
+        layout_cache: &mut LayoutCache<'a>,
+        symbol: Symbol,
+        specialization_var: Variable,
+    ) -> Symbol {
+        let arena = env.arena;
+        let subs: &Subs = env.subs;
+
+        let layout = match layout_cache.from_var(arena, specialization_var, subs) {
+            Ok(layout) => layout,
+            // This can happen when the def symbol has a type error. In such cases just use the
+            // def symbol, which is erroring.
+            Err(_) => return symbol,
+        };
+
+        let is_closure = matches!(
+            subs.get_content_without_compacting(specialization_var),
+            Content::Structure(FlatType::Func(..))
+        );
+        let function_mark = if is_closure {
+            let fn_layout = match layout_cache.raw_from_var(arena, specialization_var, subs) {
+                Ok(layout) => layout,
+                // This can happen when the def symbol has a type error. In such cases just use the
+                // def symbol, which is erroring.
+                Err(_) => return symbol,
+            };
+            Some(fn_layout)
+        } else {
+            None
+        };
+
+        let specialization_mark = SpecializationMark {
+            layout,
+            function_mark,
+        };
+
+        let symbol_specializations = self.0.get_or_insert(symbol, Default::default);
+
+        // For the first specialization, always reuse the current symbol. The vast majority of defs
+        // only have one instance type, so this preserves readability of the IR.
+        // TODO: turn me off and see what breaks.
+        let needs_fresh_symbol = !symbol_specializations.is_empty();
+
+        let mut make_specialized_symbol = || {
+            if needs_fresh_symbol {
+                env.unique_symbol()
+            } else {
+                symbol
+            }
+        };
+
+        let (_var, specialized_symbol) = symbol_specializations
+            .get_or_insert(specialization_mark, || {
+                (specialization_var, make_specialized_symbol())
+            });
+
+        *specialized_symbol
+    }
+
+    /// Inserts a known specialization for a symbol. Returns the overwritten specialization, if any.
+    pub fn get_or_insert_known(
+        &mut self,
+        symbol: Symbol,
+        mark: SpecializationMark<'a>,
+        specialization_var: Variable,
+        specialization_symbol: Symbol,
+    ) -> Option<(Variable, Symbol)> {
+        self.0
+            .get_or_insert(symbol, Default::default)
+            .insert(mark, (specialization_var, specialization_symbol))
+    }
+
+    /// Removes all specializations for a symbol, returning the type and symbol of each specialization.
+    pub fn remove(
+        &mut self,
+        symbol: Symbol,
+    ) -> impl ExactSizeIterator<Item = (SpecializationMark<'a>, (Variable, Symbol))> {
+        self.0
+            .remove(&symbol)
+            .map(|(_, specializations)| specializations)
+            .unwrap_or_default()
+            .into_iter()
+    }
+
+    /// Expects and removes at most a single specialization symbol for the given requested symbol.
+    /// A symbol may have no specializations if it is never referenced in a body, so it is possible
+    /// for this to return None.
+    pub fn remove_single(&mut self, symbol: Symbol) -> Option<Symbol> {
+        let mut specializations = self.remove(symbol);
+
+        debug_assert!(
+            specializations.len() < 2,
+            "Symbol {:?} has multiple specializations",
+            symbol
+        );
+
+        specializations.next().map(|(_, (_, symbol))| symbol)
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.0.is_empty()
+    }
+}
+
 #[derive(Clone, Debug)]
 pub struct Procs<'a> {
     pub partial_procs: PartialProcs<'a>,
@@ -753,7 +906,7 @@ pub struct Procs<'a> {
     specialized: Specialized<'a>,
     pub runtime_errors: BumpMap<Symbol, &'a str>,
     pub externals_we_need: BumpMap<ModuleId, ExternalSpecializations>,
-    pub needed_symbol_specializations: BumpMap<(Symbol, Layout<'a>), (Variable, Symbol)>,
+    symbol_specializations: SymbolSpecializations<'a>,
 }
 
 impl<'a> Procs<'a> {
@@ -767,38 +920,9 @@ impl<'a> Procs<'a> {
             specialized: Specialized::default(),
             runtime_errors: BumpMap::new_in(arena),
             externals_we_need: BumpMap::new_in(arena),
-            needed_symbol_specializations: BumpMap::new_in(arena),
+            symbol_specializations: Default::default(),
         }
     }
-
-    /// Expects and removes a single specialization symbol for the given requested symbol.
-    /// In debug builds, we assert that the layout of the specialization is the layout expected by
-    /// the requested symbol.
-    fn remove_single_symbol_specialization(
-        &mut self,
-        symbol: Symbol,
-        layout: Layout,
-    ) -> Option<Symbol> {
-        let mut specialized_symbols = self
-            .needed_symbol_specializations
-            .drain_filter(|(sym, _), _| sym == &symbol);
-
-        let specialization_symbol = specialized_symbols
-            .next()
-            .map(|((_, specialized_layout), (_, specialized_symbol))| {
-                debug_assert_eq!(specialized_layout, layout, "Requested the single specialization of {:?}, but the specialization layout ({:?}) doesn't match the expected layout ({:?})", symbol, specialized_layout, layout);
-                specialized_symbol
-            });
-
-        debug_assert_eq!(
-            specialized_symbols.count(),
-            0,
-            "Symbol {:?} has multiple specializations",
-            symbol
-        );
-
-        specialization_symbol
-    }
 }
 
 #[derive(Clone, Debug, PartialEq)]
@@ -2166,9 +2290,9 @@ pub fn specialize_all<'a>(
     specialize_host_specializations(env, &mut procs, layout_cache, specializations_for_host);
 
     debug_assert!(
-        procs.needed_symbol_specializations.is_empty(),
+        procs.symbol_specializations.is_empty(),
         "{:?}",
-        &procs.needed_symbol_specializations
+        &procs.symbol_specializations
     );
 
     procs
@@ -2503,11 +2627,10 @@ fn specialize_external<'a>(
                     // An argument from the closure list may have taken on a specialized symbol
                     // name during the evaluation of the def body. If this is the case, load the
                     // specialized name rather than the original captured name!
-                    let mut get_specialized_name = |symbol, layout| {
+                    let mut get_specialized_name = |symbol| {
                         procs
-                            .needed_symbol_specializations
+                            .symbol_specializations
-                            .remove(&(symbol, layout))
+                            .remove_single(symbol)
-                            .map(|(_, specialized)| specialized)
                             .unwrap_or(symbol)
                     };
 
@@ -2545,7 +2668,7 @@ fn specialize_external<'a>(
                                     union_layout,
                                 };
 
-                                let symbol = get_specialized_name(**symbol, **layout);
+                                let symbol = get_specialized_name(**symbol);
 
                                 specialized_body = Stmt::Let(
                                     symbol,
@@ -2588,7 +2711,7 @@ fn specialize_external<'a>(
                                     structure: Symbol::ARG_CLOSURE,
                                 };
 
-                                let symbol = get_specialized_name(**symbol, **layout);
+                                let symbol = get_specialized_name(**symbol);
 
                                 specialized_body = Stmt::Let(
                                     symbol,
@@ -2633,11 +2756,10 @@ fn specialize_external<'a>(
             let proc_args: Vec<_> = proc_args
                 .iter()
                 .map(|&(layout, symbol)| {
+                    // Grab the specialization symbol, if it exists.
                     let symbol = procs
-                        .needed_symbol_specializations
+                        .symbol_specializations
-                        // We can remove the specialization since this is the definition site.
+                        .remove_single(symbol)
-                        .remove(&(symbol, layout))
-                        .map(|(_, specialized_symbol)| specialized_symbol)
                         .unwrap_or(symbol);
 
                     (layout, symbol)
@@ -3351,18 +3473,7 @@ pub fn with_hole<'a>(
                 );
 
                 let outer_symbol = env.unique_symbol();
-                let pattern_layout = layout_cache
+                stmt = store_pattern(env, procs, layout_cache, &mono_pattern, outer_symbol, stmt);
-                    .from_var(env.arena, def.expr_var, env.subs)
-                    .expect("Pattern has no layout");
-                stmt = store_pattern(
-                    env,
-                    procs,
-                    layout_cache,
-                    &mono_pattern,
-                    pattern_layout,
-                    outer_symbol,
-                    stmt,
-                );
 
                 // convert the def body, store in outer_symbol
                 with_hole(
@@ -3405,7 +3516,9 @@ pub fn with_hole<'a>(
                 can_reuse_symbol(env, procs, &roc_can::expr::Expr::Var(symbol))
             {
                 let real_symbol =
-                    reuse_symbol_or_specialize(env, procs, layout_cache, symbol, variable);
+                    procs
+                        .symbol_specializations
+                        .get_or_insert(env, layout_cache, symbol, variable);
                 symbol = real_symbol;
             }
 
@@ -3484,8 +3597,12 @@ pub fn with_hole<'a>(
             match can_reuse_symbol(env, procs, &loc_arg_expr.value) {
                 // Opaques decay to their argument.
                 ReuseSymbol::Value(symbol) => {
-                    let real_name =
+                    let real_name = procs.symbol_specializations.get_or_insert(
-                        reuse_symbol_or_specialize(env, procs, layout_cache, symbol, arg_var);
+                        env,
+                        layout_cache,
+                        symbol,
+                        arg_var,
+                    );
                     let mut result = hole.clone();
                     substitute_in_exprs(arena, &mut result, assigned, real_name);
                     result
@@ -3538,9 +3655,8 @@ pub fn with_hole<'a>(
                             can_fields.push(Field::Function(symbol, variable));
                         }
                         Value(symbol) => {
-                            let reusable = reuse_symbol_or_specialize(
+                            let reusable = procs.symbol_specializations.get_or_insert(
                                 env,
-                                procs,
                                 layout_cache,
                                 symbol,
                                 field.var,
@@ -4353,8 +4469,20 @@ pub fn with_hole<'a>(
                                 }
                             }
                         }
-                        Value(function_symbol) => match full_layout {
+                        Value(function_symbol) => {
-                            RawFunctionLayout::Function(arg_layouts, lambda_set, ret_layout) => {
+                            let function_symbol = procs.symbol_specializations.get_or_insert(
+                                env,
+                                layout_cache,
+                                function_symbol,
+                                fn_var,
+                            );
+
+                            match full_layout {
+                                RawFunctionLayout::Function(
+                                    arg_layouts,
+                                    lambda_set,
+                                    ret_layout,
+                                ) => {
                                     let closure_data_symbol = function_symbol;
 
                                     result = match_on_lambda_set(
@@ -4371,7 +4499,8 @@ pub fn with_hole<'a>(
                                 RawFunctionLayout::ZeroArgumentThunk(_) => {
                                     unreachable!("calling a non-closure layout")
                                 }
-                        },
+                            }
+                        }
                         UnspecializedExpr(symbol) => {
                             match procs.ability_member_aliases.get(symbol).unwrap() {
                                 &AbilityMember(member) => {
@@ -5521,7 +5650,6 @@ pub fn from_can<'a>(
         }
         LetNonRec(def, cont, outer_annotation) => {
             if let roc_can::pattern::Pattern::Identifier(symbol) = &def.loc_pattern.value {
-                // dbg!(symbol, &def.loc_expr.value);
                 match def.loc_expr.value {
                     roc_can::expr::Expr::Closure(closure_data) => {
                         register_capturing_closure(env, procs, layout_cache, *symbol, closure_data);
@@ -5653,12 +5781,14 @@ pub fn from_can<'a>(
                     _ => {
                         let rest = from_can(env, variable, cont.value, procs, layout_cache);
 
-                        let needs_def_specializations = procs
+                        // Remove all the requested symbol specializations now, since this is the
-                            .needed_symbol_specializations
+                        // def site and hence we won't need them any higher up.
-                            .keys()
+                        let mut needed_specializations =
-                            .any(|(s, _)| s == symbol);
+                            procs.symbol_specializations.remove(*symbol);
 
-                        if !needs_def_specializations {
+                        if needed_specializations.len() == 0 {
+                            // We don't need any specializations, that means this symbol is never
+                            // referenced.
                             return with_hole(
                                 env,
                                 def.loc_expr.value,
@@ -5674,16 +5804,9 @@ pub fn from_can<'a>(
 
                         let mut stmt = rest;
 
-                        // Remove all the requested symbol specializations now, since this is the
-                        // def site and hence we won't need them any higher up.
-                        let mut needed_specializations = procs
-                            .needed_symbol_specializations
-                            .drain_filter(|(s, _), _| s == symbol)
-                            .collect::<std::vec::Vec<_>>();
-
                         if needed_specializations.len() == 1 {
-                            let ((_, _wanted_layout), (var, specialized_symbol)) =
+                            let (_specialization_mark, (var, specialized_symbol)) =
-                                needed_specializations.pop().unwrap();
+                                needed_specializations.next().unwrap();
 
                             // Unify the expr_var with the requested specialization once.
                             let _res =
@@ -5700,7 +5823,7 @@ pub fn from_can<'a>(
                             );
                         } else {
                             // Need to eat the cost and create a specialized version of the body for each specialization.
-                            for ((_original_symbol, _wanted_layout), (var, specialized_symbol)) in
+                            for (_specialization_mark, (var, specialized_symbol)) in
                                 needed_specializations
                             {
                                 use crate::copy::deep_copy_type_vars_into_expr;
@@ -5744,37 +5867,18 @@ pub fn from_can<'a>(
                     Err(_) => todo!(),
                 };
 
-            if let Pattern::Identifier(symbol) = mono_pattern {
+            if let Pattern::Identifier(_symbol) = mono_pattern {
-                let mut hole =
+                internal_error!("Identifier patterns should be handled in a higher code pass!")
-                    env.arena
-                        .alloc(from_can(env, variable, cont.value, procs, layout_cache));
-
-                for (symbol, variable, expr) in assignments {
-                    let stmt = with_hole(env, expr, variable, procs, layout_cache, symbol, hole);
-
-                    hole = env.arena.alloc(stmt);
             }
 
-                with_hole(
-                    env,
-                    def.loc_expr.value,
-                    def.expr_var,
-                    procs,
-                    layout_cache,
-                    symbol,
-                    hole,
-                )
-            } else {
             // convert the continuation
             let mut stmt = from_can(env, variable, cont.value, procs, layout_cache);
 
             // layer on any default record fields
             for (symbol, variable, expr) in assignments {
-                    let layout = layout_cache
-                        .from_var(env.arena, variable, env.subs)
-                        .expect("Default field has no layout");
                 let specialization_symbol = procs
-                        .remove_single_symbol_specialization(symbol, layout)
+                    .symbol_specializations
+                    .remove_single(symbol)
                     // Can happen when the symbol was never used under this body, and hence has no
                     // requested specialization.
                     .unwrap_or(symbol);
@@ -5791,30 +5895,11 @@ pub fn from_can<'a>(
                 );
             }
 
-                let pattern_layout = layout_cache
-                    .from_var(env.arena, def.expr_var, env.subs)
-                    .expect("Pattern has no layout");
             if let roc_can::expr::Expr::Var(outer_symbol) = def.loc_expr.value {
-                    store_pattern(
+                store_pattern(env, procs, layout_cache, &mono_pattern, outer_symbol, stmt)
-                        env,
-                        procs,
-                        layout_cache,
-                        &mono_pattern,
-                        pattern_layout,
-                        outer_symbol,
-                        stmt,
-                    )
             } else {
                 let outer_symbol = env.unique_symbol();
-                    stmt = store_pattern(
+                stmt = store_pattern(env, procs, layout_cache, &mono_pattern, outer_symbol, stmt);
-                        env,
-                        procs,
-                        layout_cache,
-                        &mono_pattern,
-                        pattern_layout,
-                        outer_symbol,
-                        stmt,
-                    );
 
                 // convert the def body, store in outer_symbol
                 with_hole(
@@ -5828,7 +5913,6 @@ pub fn from_can<'a>(
                 )
             }
         }
-        }
 
         _ => {
             let symbol = env.unique_symbol();
@@ -6380,19 +6464,10 @@ pub fn store_pattern<'a>(
     procs: &mut Procs<'a>,
     layout_cache: &mut LayoutCache<'a>,
     can_pat: &Pattern<'a>,
-    pattern_layout: Layout,
     outer_symbol: Symbol,
     stmt: Stmt<'a>,
 ) -> Stmt<'a> {
-    match store_pattern_help(
+    match store_pattern_help(env, procs, layout_cache, can_pat, outer_symbol, stmt) {
-        env,
-        procs,
-        layout_cache,
-        can_pat,
-        pattern_layout,
-        outer_symbol,
-        stmt,
-    ) {
         StorePattern::Productive(new) => new,
         StorePattern::NotProductive(new) => new,
     }
@@ -6412,7 +6487,6 @@ fn store_pattern_help<'a>(
     procs: &mut Procs<'a>,
     layout_cache: &mut LayoutCache<'a>,
     can_pat: &Pattern<'a>,
-    pattern_layout: Layout,
     outer_symbol: Symbol,
     mut stmt: Stmt<'a>,
 ) -> StorePattern<'a> {
@@ -6423,7 +6497,8 @@ fn store_pattern_help<'a>(
             // An identifier in a pattern can define at most one specialization!
             // Remove any requested specializations for this name now, since this is the definition site.
             let specialization_symbol = procs
-                .remove_single_symbol_specialization(*symbol, pattern_layout)
+                .symbol_specializations
+                .remove_single(*symbol)
                 // Can happen when the symbol was never used under this body, and hence has no
                 // requested specialization.
                 .unwrap_or(*symbol);
@@ -6444,16 +6519,8 @@ fn store_pattern_help<'a>(
             return StorePattern::NotProductive(stmt);
         }
         NewtypeDestructure { arguments, .. } => match arguments.as_slice() {
-            [(pattern, layout)] => {
+            [(pattern, _layout)] => {
-                return store_pattern_help(
+                return store_pattern_help(env, procs, layout_cache, pattern, outer_symbol, stmt);
-                    env,
-                    procs,
-                    layout_cache,
-                    pattern,
-                    *layout,
-                    outer_symbol,
-                    stmt,
-                );
             }
             _ => {
                 let mut fields = Vec::with_capacity_in(arguments.len(), env.arena);
@@ -6490,16 +6557,8 @@ fn store_pattern_help<'a>(
             );
         }
         OpaqueUnwrap { argument, .. } => {
-            let (pattern, layout) = &**argument;
+            let (pattern, _layout) = &**argument;
-            return store_pattern_help(
+            return store_pattern_help(env, procs, layout_cache, pattern, outer_symbol, stmt);
-                env,
-                procs,
-                layout_cache,
-                pattern,
-                *layout,
-                outer_symbol,
-                stmt,
-            );
         }
 
         RecordDestructure(destructs, [_single_field]) => {
@@ -6507,7 +6566,8 @@ fn store_pattern_help<'a>(
                 match &destruct.typ {
                     DestructType::Required(symbol) => {
                         let specialization_symbol = procs
-                            .remove_single_symbol_specialization(*symbol, destruct.layout)
+                            .symbol_specializations
+                            .remove_single(*symbol)
                             // Can happen when the symbol was never used under this body, and hence has no
                             // requested specialization.
                             .unwrap_or(*symbol);
@@ -6525,7 +6585,6 @@ fn store_pattern_help<'a>(
                             procs,
                             layout_cache,
                             guard_pattern,
-                            destruct.layout,
                             outer_symbol,
                             stmt,
                         );
@@ -6598,7 +6657,8 @@ fn store_tag_pattern<'a>(
             Identifier(symbol) => {
                 // Pattern can define only one specialization
                 let symbol = procs
-                    .remove_single_symbol_specialization(*symbol, arg_layout)
+                    .symbol_specializations
+                    .remove_single(*symbol)
                     .unwrap_or(*symbol);
 
                 // store immediately in the given symbol
@@ -6619,15 +6679,7 @@ fn store_tag_pattern<'a>(
                 let symbol = env.unique_symbol();
 
                 // first recurse, continuing to unpack symbol
-                match store_pattern_help(
+                match store_pattern_help(env, procs, layout_cache, argument, symbol, stmt) {
-                    env,
-                    procs,
-                    layout_cache,
-                    argument,
-                    arg_layout,
-                    symbol,
-                    stmt,
-                ) {
                     StorePattern::Productive(new) => {
                         is_productive = true;
                         stmt = new;
@@ -6687,7 +6739,8 @@ fn store_newtype_pattern<'a>(
             Identifier(symbol) => {
                 // store immediately in the given symbol, removing it specialization if it had any
                 let specialization_symbol = procs
-                    .remove_single_symbol_specialization(*symbol, arg_layout)
+                    .symbol_specializations
+                    .remove_single(*symbol)
                     // Can happen when the symbol was never used under this body, and hence has no
                     // requested specialization.
                     .unwrap_or(*symbol);
@@ -6714,15 +6767,7 @@ fn store_newtype_pattern<'a>(
                 let symbol = env.unique_symbol();
 
                 // first recurse, continuing to unpack symbol
-                match store_pattern_help(
+                match store_pattern_help(env, procs, layout_cache, argument, symbol, stmt) {
-                    env,
-                    procs,
-                    layout_cache,
-                    argument,
-                    arg_layout,
-                    symbol,
-                    stmt,
-                ) {
                     StorePattern::Productive(new) => {
                         is_productive = true;
                         stmt = new;
@@ -6770,7 +6815,8 @@ fn store_record_destruct<'a>(
             // A destructure can define at most one specialization!
             // Remove any requested specializations for this name now, since this is the definition site.
             let specialization_symbol = procs
-                .remove_single_symbol_specialization(*symbol, destruct.layout)
+                .symbol_specializations
+                .remove_single(*symbol)
                 // Can happen when the symbol was never used under this body, and hence has no
                 // requested specialization.
                 .unwrap_or(*symbol);
@@ -6785,7 +6831,8 @@ fn store_record_destruct<'a>(
         DestructType::Guard(guard_pattern) => match &guard_pattern {
             Identifier(symbol) => {
                 let specialization_symbol = procs
-                    .remove_single_symbol_specialization(*symbol, destruct.layout)
+                    .symbol_specializations
+                    .remove_single(*symbol)
                     // Can happen when the symbol was never used under this body, and hence has no
                     // requested specialization.
                     .unwrap_or(*symbol);
@@ -6823,15 +6870,7 @@ fn store_record_destruct<'a>(
             _ => {
                 let symbol = env.unique_symbol();
 
-                match store_pattern_help(
+                match store_pattern_help(env, procs, layout_cache, guard_pattern, symbol, stmt) {
-                    env,
-                    procs,
-                    layout_cache,
-                    guard_pattern,
-                    destruct.layout,
-                    symbol,
-                    stmt,
-                ) {
                     StorePattern::Productive(new) => {
                         stmt = new;
                         stmt = Stmt::Let(symbol, load, destruct.layout, env.arena.alloc(stmt));
@@ -6894,45 +6933,6 @@ fn can_reuse_symbol<'a>(
     }
 }
 
-/// Reuses the specialized symbol for a given symbol and instance type. If no specialization symbol
-/// yet exists, one is created.
-fn reuse_symbol_or_specialize<'a>(
-    env: &mut Env<'a, '_>,
-    procs: &mut Procs<'a>,
-    layout_cache: &mut LayoutCache<'a>,
-    symbol: Symbol,
-    var: Variable,
-) -> Symbol {
-    let wanted_layout = match layout_cache.from_var(env.arena, var, env.subs) {
-        Ok(layout) => layout,
-        // This can happen when the def symbol has a type error. In such cases just use the
-        // def symbol, which is erroring.
-        Err(_) => return symbol,
-    };
-
-    // For the first specialization, always reuse the current symbol. The vast majority of defs
-    // only have one instance type, so this preserves readability of the IR.
-    let needs_fresh_symbol = procs
-        .needed_symbol_specializations
-        .keys()
-        .any(|(s, _)| *s == symbol);
-
-    let mut make_specialized_symbol = || {
-        if needs_fresh_symbol {
-            env.unique_symbol()
-        } else {
-            symbol
-        }
-    };
-
-    let (_, specialized_symbol) = procs
-        .needed_symbol_specializations
-        .entry((symbol, wanted_layout))
-        .or_insert_with(|| (var, make_specialized_symbol()));
-
-    *specialized_symbol
-}
-
 fn possible_reuse_symbol_or_specialize<'a>(
     env: &mut Env<'a, '_>,
     procs: &mut Procs<'a>,
@@ -6942,7 +6942,9 @@ fn possible_reuse_symbol_or_specialize<'a>(
 ) -> Symbol {
     match can_reuse_symbol(env, procs, expr) {
         ReuseSymbol::Value(symbol) => {
-            reuse_symbol_or_specialize(env, procs, layout_cache, symbol, var)
+            procs
+                .symbol_specializations
+                .get_or_insert(env, layout_cache, symbol, var)
         }
         _ => env.unique_symbol(),
     }
@@ -6987,16 +6989,13 @@ where
     let result = build_rest(env, procs, layout_cache);
 
     // The specializations we wanted of the symbol on the LHS of this alias.
-    let needed_specializations_of_left = procs
+    let needed_specializations_of_left = procs.symbol_specializations.remove(left);
-        .needed_symbol_specializations
-        .drain_filter(|(s, _), _| s == &left)
-        .collect::<std::vec::Vec<_>>();
 
     if procs.is_imported_module_thunk(right) {
         // if this is an imported symbol, then we must make sure it is
         // specialized, and wrap the original in a function pointer.
         let mut result = result;
-        for (_, (variable, left)) in needed_specializations_of_left.into_iter() {
+        for (_, (variable, left)) in needed_specializations_of_left {
             add_needed_external(procs, env, variable, right);
 
             let res_layout = layout_cache.from_var(env.arena, variable, env.subs);
@@ -7016,14 +7015,17 @@ where
         // We need to lift all specializations of "left" to be specializations of "right".
         let mut scratchpad_update_specializations = std::vec::Vec::new();
 
-        let left_had_specialization_symbols = !needed_specializations_of_left.is_empty();
+        let left_had_specialization_symbols = needed_specializations_of_left.len() > 0;
 
-        for ((_, layout), (specialized_var, specialized_sym)) in
+        for (specialization_mark, (specialized_var, specialized_sym)) in
-            needed_specializations_of_left.into_iter()
+            needed_specializations_of_left
         {
-            let old_specialized_sym = procs
+            let old_specialized_sym = procs.symbol_specializations.get_or_insert_known(
-                .needed_symbol_specializations
+                right,
-                .insert((right, layout), (specialized_var, specialized_sym));
+                specialization_mark,
+                specialized_var,
+                specialized_sym,
+            );
 
             if let Some((_, old_specialized_sym)) = old_specialized_sym {
                 scratchpad_update_specializations.push((old_specialized_sym, specialized_sym));

compiler/solve/src/solve.rs

@@ -476,10 +476,13 @@ impl Pools {
         self.0.iter()
     }
 
-    pub fn split_last(&self) -> (&Vec<Variable>, &[Vec<Variable>]) {
+    pub fn split_last(mut self) -> (Vec<Variable>, Vec<Vec<Variable>>) {
-        self.0
+        let last = self
-            .split_last()
+            .0
-            .unwrap_or_else(|| panic!("Attempted to split_last() on non-empty Pools"))
+            .pop()
+            .unwrap_or_else(|| panic!("Attempted to split_last() on non-empty Pools"));
+
+        (last, self.0)
     }
 
     pub fn extend_to(&mut self, n: usize) {
@@ -737,8 +740,7 @@ fn solve(
 
                 // pop pool
                 generalize(subs, young_mark, visit_mark, next_rank, pools);
-
+                debug_assert!(pools.get(next_rank).is_empty());
-                pools.get_mut(next_rank).clear();
 
                 // check that things went well
                 dbg_do!(ROC_VERIFY_RIGID_LET_GENERALIZED, {
@@ -2426,7 +2428,7 @@ fn generalize(
     young_rank: Rank,
     pools: &mut Pools,
 ) {
-    let young_vars = pools.get(young_rank);
+    let young_vars = std::mem::take(pools.get_mut(young_rank));
     let rank_table = pool_to_rank_table(subs, young_mark, young_rank, young_vars);
 
     // Get the ranks right for each entry.
@@ -2437,12 +2439,12 @@ fn generalize(
         }
     }
 
-    let (last_pool, all_but_last_pool) = rank_table.split_last();
+    let (mut last_pool, all_but_last_pool) = rank_table.split_last();
 
     // For variables that have rank lowerer than young_rank, register them in
     // the appropriate old pool if they are not redundant.
     for vars in all_but_last_pool {
-        for &var in vars {
+        for var in vars {
             if !subs.redundant(var) {
                 let rank = subs.get_rank(var);
 
@@ -2453,7 +2455,7 @@ fn generalize(
 
     // For variables with rank young_rank, if rank < young_rank: register in old pool,
     // otherwise generalize
-    for &var in last_pool {
+    for var in last_pool.drain(..) {
         if !subs.redundant(var) {
             let desc_rank = subs.get_rank(var);
 
@@ -2464,32 +2466,38 @@ fn generalize(
             }
         }
     }
+
+    // re-use the last_vector (which likely has a good capacity for future runs
+    *pools.get_mut(young_rank) = last_pool;
 }
 
 /// Sort the variables into buckets by rank.
+#[inline]
 fn pool_to_rank_table(
     subs: &mut Subs,
     young_mark: Mark,
     young_rank: Rank,
-    young_vars: &[Variable],
+    mut young_vars: Vec<Variable>,
 ) -> Pools {
     let mut pools = Pools::new(young_rank.into_usize() + 1);
 
     // the vast majority of young variables have young_rank
-    // using `retain` here prevents many `pools.get_mut(young_rank)` lookups
+    let mut i = 0;
-    let mut young_vars = young_vars.to_vec();
+    while i < young_vars.len() {
-    young_vars.retain(|var| {
+        let var = young_vars[i];
-        let rank = subs.get_rank_set_mark(*var, young_mark);
+        let rank = subs.get_rank_set_mark(var, young_mark);
 
         if rank != young_rank {
             debug_assert!(rank.into_usize() < young_rank.into_usize() + 1);
 
-            pools.get_mut(rank).push(*var);
+            pools.get_mut(rank).push(var);
-            false
+
+            // swap an element in; don't increment i
+            young_vars.swap_remove(i);
         } else {
-            true
+            i += 1;
+        }
     }
-    });
 
     std::mem::swap(pools.get_mut(young_rank), &mut young_vars);
 

compiler/solve/tests/solve_expr.rs

@@ -6234,4 +6234,22 @@ mod solve_expr {
             "F b -> b",
         )
     }
+
+    #[test]
+    fn alias_in_opaque() {
+        infer_eq_without_problem(
+            indoc!(
+                r#"
+                app "test" provides [ foo ] to "./platform"
+
+                MyError : [ Error ]
+
+                MyResult := Result U8 MyError
+
+                foo = @MyResult (Err Error)
+                "#
+            ),
+            "MyResult",
+        )
+    }
 }

compiler/test_gen/src/gen_num.rs

@@ -3270,3 +3270,51 @@ fn dec_float_suffix() {
         i128
     );
 }
+
+#[test]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+fn ceiling_to_u32() {
+    assert_evals_to!(
+        indoc!(
+            r#"
+            n : U32
+            n = Num.ceiling 124.5
+            n
+            "#
+        ),
+        125,
+        u32
+    );
+}
+
+#[test]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+fn floor_to_u32() {
+    assert_evals_to!(
+        indoc!(
+            r#"
+            n : U32
+            n = Num.floor 124.5
+            n
+            "#
+        ),
+        124,
+        u32
+    );
+}
+
+#[test]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+fn round_to_u32() {
+    assert_evals_to!(
+        indoc!(
+            r#"
+            n : U32
+            n = Num.round 124.49
+            n
+            "#
+        ),
+        124,
+        u32
+    );
+}

compiler/test_gen/src/gen_primitives.rs

@@ -3267,7 +3267,6 @@ fn polymophic_expression_captured_inside_closure() {
 
 #[test]
 #[cfg(any(feature = "gen-llvm"))]
-#[ignore = "Compile polymorphic functions"]
 fn issue_2322() {
     assert_evals_to!(
         indoc!(
@@ -3421,7 +3420,6 @@ fn polymorphic_def_used_in_closure() {
 
 #[test]
 #[cfg(any(feature = "gen-llvm"))]
-#[ignore = "This still doesn't work... yet"]
 fn polymorphic_lambda_set_usage() {
     assert_evals_to!(
         indoc!(
@@ -3429,6 +3427,7 @@ fn polymorphic_lambda_set_usage() {
             id1 = \x -> x
             id2 = \y -> y
             id = if True then id1 else id2
+
             id 9u8
             "#
         ),
@@ -3436,3 +3435,21 @@ fn polymorphic_lambda_set_usage() {
         u8
     )
 }
+
+#[test]
+#[cfg(any(feature = "gen-llvm"))]
+fn polymorphic_lambda_set_multiple_specializations() {
+    assert_evals_to!(
+        indoc!(
+            r#"
+            id1 = \x -> x
+            id2 = \y -> y
+            id = if True then id1 else id2
+
+            (id 9u8) + Num.toU8 (id 16u16)
+            "#
+        ),
+        25,
+        u8
+    )
+}

compiler/test_gen/src/helpers/llvm.rs

@@ -60,7 +60,7 @@ fn create_llvm_module<'a>(
         Default::default(),
         target_info,
         RenderTarget::ColorTerminal,
-        Threading::Multi,
+        Threading::AllAvailable,
     );
 
     let mut loaded = match loaded {

compiler/test_mono/Cargo.toml

@@ -19,6 +19,5 @@ roc_mono = { path = "../mono" }
 roc_target = { path = "../roc_target" }
 roc_reporting = { path = "../../reporting" }
 test_mono_macros = { path = "../test_mono_macros" }
-pretty_assertions = "1.0.0"
 bumpalo = { version = "3.8.0", features = ["collections"] }
 indoc = "1.0.3"

compiler/types/src/types.rs

@@ -1123,8 +1123,17 @@ impl Type {
                     ext.instantiate_aliases(region, aliases, var_store, new_lambda_set_variables);
                 }
             }
-            DelayedAlias(AliasCommon { .. }) => {
+            DelayedAlias(AliasCommon {
-                // do nothing, yay
+                type_arguments,
+                lambda_set_variables,
+                symbol: _,
+            }) => {
+                debug_assert!(lambda_set_variables
+                    .iter()
+                    .all(|lambda_set| matches!(lambda_set.0, Type::Variable(..))));
+                type_arguments.iter_mut().for_each(|t| {
+                    t.instantiate_aliases(region, aliases, var_store, new_lambda_set_variables)
+                });
             }
             HostExposedAlias {
                 type_arguments: type_args,

docs/Cargo.toml

@@ -28,6 +28,3 @@ peg = "0.8.0"
 
 [dev-dependencies]
 pretty_assertions = "1.0.0"
-tempfile = "3.2.0"
-uuid = { version = "0.8.2", features = ["v4"] }
-indoc = "1.0.3"

docs/src/lib.rs

@@ -435,7 +435,7 @@ pub fn load_modules_for_files(filenames: Vec<PathBuf>) -> Vec<LoadedModule> {
             Default::default(),
             roc_target::TargetInfo::default_x86_64(), // This is just type-checking for docs, so "target" doesn't matter
             roc_reporting::report::RenderTarget::ColorTerminal,
-            Threading::Multi,
+            Threading::AllAvailable,
         ) {
             Ok(loaded) => modules.push(loaded),
             Err(LoadingProblem::FormattedReport(report)) => {

editor/src/editor/main.rs

@@ -129,7 +129,7 @@ fn run_event_loop(project_dir_path_opt: Option<&Path>) -> Result<(), Box<dyn Err
 
     let file_path = Path::new(&file_path_str);
 
-    let loaded_module = load_module(file_path, Threading::Multi);
+    let loaded_module = load_module(file_path, Threading::AllAvailable);
 
     let mut var_store = VarStore::default();
     let dep_idents = IdentIds::exposed_builtins(8);

editor/src/editor/mvc/ed_model.rs

@@ -330,7 +330,7 @@ pub mod test_ed_model {
         writeln!(file, "{}", clean_code_str)
             .unwrap_or_else(|_| panic!("Failed to write {:?} to file: {:?}", clean_code_str, file));
 
-        let loaded_module = load_module(&temp_file_full_path, Threading::Multi);
+        let loaded_module = load_module(&temp_file_full_path, Threading::AllAvailable);
 
         let mut ed_model = init_dummy_model(
             clean_code_str,

examples/false-interpreter/platform/src/lib.rs

@@ -74,7 +74,9 @@ pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut
 
 #[no_mangle]
 pub extern "C" fn rust_main() -> i32 {
-    let arg = env::args().nth(1).unwrap();
+    let arg = env::args()
+        .nth(1)
+        .expect("Please pass a .false file as a command-line argument to the false interpreter!");
     let arg = RocStr::from(arg.as_str());
 
     let size = unsafe { roc_main_size() } as usize;

reporting/Cargo.toml

@@ -29,4 +29,3 @@ roc_target = { path = "../compiler/roc_target" }
 roc_test_utils = { path = "../test_utils" }
 pretty_assertions = "1.0.0"
 indoc = "1.0.3"
-tempfile = "3.2.0"