Merge remote-tracking branch 'origin/main' into packages

.github/workflows/nightly_macos_x86_64.yml

@@ -15,16 +15,15 @@ jobs:
       - name: write version to file
         run: ./ci/write_version.sh
           
-      # build has to be done before tests #2572
-      - name: build release
-        run: RUSTFLAGS="-C target-cpu=x86-64" cargo build --features with_sound --release --locked
-        # target-cpu=x86-64 -> For maximal compatibility for all CPU's. Note that this setting will likely make the compiler slower.
-          
       - name: execute rust tests
         run: cargo test --release --locked -- --skip opaque_wrap_function --skip bool_list_literal --skip platform_switching_swift --skip swift_ui
         # swift tests are skipped because of "Could not find or use auto-linked library 'swiftCompatibilityConcurrency'" on macos-11 x86_64 CI machine
         # this issue may be caused by using older versions of XCode
 
+      - name: build release
+        run: RUSTFLAGS="-C target-cpu=x86-64" cargo build --features with_sound --release --locked
+        # target-cpu=x86-64 -> For maximal compatibility for all CPU's. Note that this setting will likely make the compiler slower.
+          
       - name: get commit SHA
         run:  echo "SHA=$(git rev-parse --short "$GITHUB_SHA")" >> $GITHUB_ENV
         

Cargo.lock

@@ -3700,6 +3700,7 @@ dependencies = [
  "roc_serialize",
  "roc_types",
  "static_assertions",
+ "ven_pretty",
 ]
 
 [[package]]

crates/cli/Cargo.toml

@@ -39,6 +39,8 @@ target-all = [
     "target-wasm32"
 ]
 
+sanitizers = ["roc_build/sanitizers"]
+
 
 [dependencies]
 roc_collections = { path = "../compiler/collections" }

crates/cli/src/build.rs

@@ -186,7 +186,9 @@ pub fn build_file<'a>(
     };
 
     // We don't need to spawn a rebuild thread when using a prebuilt host.
-    let rebuild_thread = if is_prebuilt {
+    let rebuild_thread = if matches!(link_type, LinkType::Dylib | LinkType::None) {
+        None
+    } else if is_prebuilt {
         if !preprocessed_host_path.exists() {
             if prebuilt_requested {
                 eprintln!(
@@ -378,10 +380,11 @@ pub fn build_file<'a>(
 
             std::fs::write(app_o_file, &*roc_app_bytes).unwrap();
 
-            let mut inputs = vec![
+            let mut inputs = vec![app_o_file.to_str().unwrap()];
-                host_input_path.as_path().to_str().unwrap(),
+
-                app_o_file.to_str().unwrap(),
+            if !matches!(link_type, LinkType::Dylib | LinkType::None) {
-            ];
+                inputs.push(host_input_path.as_path().to_str().unwrap());
+            }
 
             let builtins_host_tempfile = {
                 #[cfg(unix)]

crates/cli/tests/cli_run.rs

@@ -568,7 +568,7 @@ mod cli_run {
                 r#"
                 This expectation failed:
 
-                14│      expect x != x
+                18│      expect x != x
                                 ^^^^^^
 
                 When it failed, these variables had these values:
@@ -576,8 +576,11 @@ mod cli_run {
                 x : Num *
                 x = 42
 
-                [<ignored for tests> 15:9] 42
+                [<ignored for tests> 19:9] 42
-                [<ignored for tests> 16:9] "Fjoer en ferdjer frieten oan dyn geve lea"
+                [<ignored for tests> 20:9] "Fjoer en ferdjer frieten oan dyn geve lea"
+                [<ignored for tests> 13:9] "abc"
+                [<ignored for tests> 13:9] 10
+                [<ignored for tests> 13:9] A (B C)
                 Program finished!
                 "#
             ),

crates/cli_testing_examples/expects/expects.roc

@@ -9,9 +9,17 @@ expect
 
     a == b
 
+polyDbg = \x ->
+    dbg x
+    x
+
 main =
     x = 42
     expect x != x
     dbg x
     dbg "Fjoer en ferdjer frieten oan dyn geve lea"
-    "Program finished!\n"
+
+    r = {x : polyDbg "abc", y: polyDbg 10u8, z : polyDbg (A (B C))}
+
+    when r is
+        _ -> "Program finished!\n"

crates/compiler/alias_analysis/src/lib.rs

@@ -1287,6 +1287,14 @@ fn lowlevel_spec<'a>(
 
             builder.add_make_tuple(block, &[byte_index, string, is_ok, problem_code])
         }
+        Dbg => {
+            let arguments = [env.symbols[&arguments[0]]];
+
+            let result_type =
+                layout_spec(env, builder, interner, layout, &WhenRecursive::Unreachable)?;
+
+            builder.add_unknown_with(block, &arguments, result_type)
+        }
         _other => {
             // println!("missing {:?}", _other);
             // TODO overly pessimstic

crates/compiler/build/Cargo.toml

@@ -47,3 +47,7 @@ target-aarch64 = ["roc_gen_dev/target-aarch64"]
 target-x86 = []
 target-x86_64 = ["roc_gen_dev/target-x86_64"]
 target-wasm32 = []
+
+# This is used to enable fuzzing and sanitizers.
+# Example use is describe here: https://github.com/bhansconnect/roc-fuzz
+sanitizers = []

crates/compiler/build/src/link.rs

@@ -1248,14 +1248,17 @@ fn link_macos(
     input_paths: &[&str],
     link_type: LinkType,
 ) -> io::Result<(Child, PathBuf)> {
-    let (link_type_arg, output_path) = match link_type {
+    let (link_type_args, output_path) = match link_type {
-        LinkType::Executable => ("-execute", output_path),
+        LinkType::Executable => (vec!["-execute"], output_path),
         LinkType::Dylib => {
             let mut output_path = output_path;
 
             output_path.set_extension("dylib");
 
-            ("-dylib", output_path)
+            (
+                vec!["-dylib", "-undefined", "dynamic_lookup", "-no_fixup_chains"],
+                output_path,
+            )
         }
         LinkType::None => internal_error!("link_macos should not be called with link type of none"),
     };
@@ -1272,13 +1275,13 @@ fn link_macos(
         // The `-l` flags should go after the `.o` arguments
         // Don't allow LD_ env vars to affect this
         .env_clear()
+        .args(&link_type_args)
         .args([
             // NOTE: we don't do --gc-sections on macOS because the default
             // macOS linker doesn't support it, but it's a performance
             // optimization, so if we ever switch to a different linker,
             // we'd like to re-enable it on macOS!
             // "--gc-sections",
-            link_type_arg,
             "-arch",
             &arch,
             "-macos_version_min",

crates/compiler/build/src/program.rs

@@ -237,15 +237,94 @@ fn gen_from_mono_module_llvm<'a>(
 
     // annotate the LLVM IR output with debug info
     // so errors are reported with the line number of the LLVM source
-    let memory_buffer = if emit_debug_info {
+    let memory_buffer = if cfg!(feature = "sanitizers") && std::env::var("ROC_SANITIZERS").is_ok() {
+        let dir = tempfile::tempdir().unwrap();
+        let dir = dir.into_path();
+
+        let app_ll_file = dir.join("app.ll");
+        let app_bc_file = dir.join("app.bc");
+        let app_o_file = dir.join("app.o");
+
+        // write the ll code to a file, so we can modify it
+        module.print_to_file(&app_ll_file).unwrap();
+
+        // Apply coverage passes.
+        // Note, this is specifically tailored for `cargo afl` and afl++.
+        // It most likely will not work with other fuzzer setups without modification.
+        let mut passes = vec![];
+        let mut extra_args = vec![];
+        let mut unrecognized = vec![];
+        for sanitizer in std::env::var("ROC_SANITIZERS")
+            .unwrap()
+            .split(',')
+            .map(|x| x.trim())
+        {
+            match sanitizer {
+                "address" => passes.push("asan-module"),
+                "memory" => passes.push("msan-module"),
+                "thread" => passes.push("tsan-module"),
+                "fuzzer" => {
+                    passes.push("sancov-module");
+                    extra_args.extend_from_slice(&[
+                        "-sanitizer-coverage-level=3",
+                        "-sanitizer-coverage-prune-blocks=0",
+                        "-sanitizer-coverage-trace-pc-guard",
+                        // This can be used instead of the line above to enable working with `cargo fuzz` and libFuzzer.
+                        // "-sanitizer-coverage-inline-8bit-counters",
+                    ]);
+                }
+                x => unrecognized.push(x.to_owned()),
+            }
+        }
+        if !unrecognized.is_empty() {
+            let out = unrecognized
+                .iter()
+                .map(|x| format!("{:?}", x))
+                .collect::<Vec<String>>()
+                .join(", ");
+            eprintln!("Unrecognized sanitizer: {}\nSupported options are \"address\", \"memory\", \"thread\", and \"fuzzer\"", out);
+        }
+
+        use std::process::Command;
+        let mut opt = Command::new("opt");
+        opt.args([
+            app_ll_file.to_str().unwrap(),
+            "-o",
+            app_bc_file.to_str().unwrap(),
+        ])
+        .args(extra_args);
+        if !passes.is_empty() {
+            opt.arg(format!("-passes={}", passes.join(",")));
+        }
+        let opt = opt.output().unwrap();
+
+        assert!(opt.stderr.is_empty(), "{:#?}", opt);
+
+        // write the .o file. Note that this builds the .o for the local machine,
+        // and ignores the `target_machine` entirely.
+        //
+        // different systems name this executable differently, so we shotgun for
+        // the most common ones and then give up.
+        let bc_to_object = Command::new("llc")
+            .args(&[
+                "-relocation-model=pic",
+                "-filetype=obj",
+                app_bc_file.to_str().unwrap(),
+                "-o",
+                app_o_file.to_str().unwrap(),
+            ])
+            .output()
+            .unwrap();
+
+        assert!(bc_to_object.status.success(), "{:#?}", bc_to_object);
+
+        MemoryBuffer::create_from_file(&app_o_file).expect("memory buffer creation works")
+    } else if emit_debug_info {
         module.strip_debug_info();
 
         let mut app_ll_dbg_file = PathBuf::from(roc_file_path);
         app_ll_dbg_file.set_extension("dbg.ll");
 
-        let mut app_bc_file = PathBuf::from(roc_file_path);
-        app_bc_file.set_extension("bc");
-
         let mut app_o_file = PathBuf::from(roc_file_path);
         app_o_file.set_extension("o");
 
@@ -277,33 +356,23 @@ fn gen_from_mono_module_llvm<'a>(
             | Architecture::X86_32(_)
             | Architecture::Aarch64(_)
             | Architecture::Wasm32 => {
-                let ll_to_bc = Command::new("llvm-as")
-                    .args([
-                        app_ll_dbg_file.to_str().unwrap(),
-                        "-o",
-                        app_bc_file.to_str().unwrap(),
-                    ])
-                    .output()
-                    .unwrap();
-
-                assert!(ll_to_bc.stderr.is_empty(), "{:#?}", ll_to_bc);
-
-                let llc_args = &[
-                    "-relocation-model=pic",
-                    "-filetype=obj",
-                    app_bc_file.to_str().unwrap(),
-                    "-o",
-                    app_o_file.to_str().unwrap(),
-                ];
-
                 // write the .o file. Note that this builds the .o for the local machine,
                 // and ignores the `target_machine` entirely.
                 //
                 // different systems name this executable differently, so we shotgun for
                 // the most common ones and then give up.
-                let bc_to_object = Command::new("llc").args(llc_args).output().unwrap();
+                let ll_to_object = Command::new("llc")
+                    .args(&[
+                        "-relocation-model=pic",
+                        "-filetype=obj",
+                        app_ll_dbg_file.to_str().unwrap(),
+                        "-o",
+                        app_o_file.to_str().unwrap(),
+                    ])
+                    .output()
+                    .unwrap();
 
-                assert!(bc_to_object.stderr.is_empty(), "{:#?}", bc_to_object);
+                assert!(ll_to_object.stderr.is_empty(), "{:#?}", ll_to_object);
             }
             _ => unreachable!(),
         }

crates/compiler/builtins/src/bitcode.rs

@@ -73,7 +73,6 @@ pub enum DecWidth {
 pub enum FloatWidth {
     F32,
     F64,
-    F128,
 }
 
 impl FloatWidth {
@@ -86,7 +85,6 @@ impl FloatWidth {
         match self {
             F32 => 4,
             F64 => 8,
-            F128 => 16,
         }
     }
 
@@ -99,7 +97,7 @@ impl FloatWidth {
         // the compiler is targeting (e.g. what the Roc code will be compiled to).
         match self {
             F32 => 4,
-            F64 | F128 => match target_info.architecture {
+            F64 => match target_info.architecture {
                 X86_64 | Aarch64 | Wasm32 => 8,
                 X86_32 | Aarch32 => 4,
             },
@@ -225,7 +223,6 @@ impl Index<FloatWidth> for IntrinsicName {
         match index {
             FloatWidth::F32 => self.options[1],
             FloatWidth::F64 => self.options[2],
-            FloatWidth::F128 => self.options[3],
         }
     }
 }
@@ -256,7 +253,6 @@ macro_rules! float_intrinsic {
 
         output.options[1] = concat!($name, ".f32");
         output.options[2] = concat!($name, ".f64");
-        output.options[3] = concat!($name, ".f128");
 
         output
     }};

crates/compiler/can/Cargo.toml

@@ -21,6 +21,8 @@ bumpalo.workspace = true
 static_assertions.workspace = true
 bitvec.workspace = true
 
+ven_pretty = { path = "../../vendor/pretty" }
+
 [dev-dependencies]
 pretty_assertions.workspace = true
 indoc.workspace = true

crates/compiler/can/src/debug.rs

@@ -0,0 +1,5 @@
+mod pretty_print;
+
+pub use pretty_print::pretty_print_declarations;
+pub use pretty_print::pretty_print_def;
+pub use pretty_print::Ctx as PPCtx;

crates/compiler/can/src/debug/pretty_print.rs

@@ -1,16 +1,50 @@
 //! Pretty-prints the canonical AST back to check our work - do things look reasonable?
 
-use roc_can::def::Def;
+use crate::def::Def;
-use roc_can::expr::Expr::{self, *};
+use crate::expr::Expr::{self, *};
-use roc_can::expr::{ClosureData, OpaqueWrapFunctionData, WhenBranch};
+use crate::expr::{
-use roc_can::pattern::{Pattern, RecordDestruct};
+    ClosureData, DeclarationTag, Declarations, FunctionDef, OpaqueWrapFunctionData, WhenBranch,
+};
+use crate::pattern::{Pattern, RecordDestruct};
 
-use roc_module::symbol::Interns;
+use roc_module::symbol::{Interns, ModuleId, Symbol};
 
 use ven_pretty::{Arena, DocAllocator, DocBuilder};
 
 pub struct Ctx<'a> {
+    pub home: ModuleId,
     pub interns: &'a Interns,
+    pub print_lambda_names: bool,
+}
+
+pub fn pretty_print_declarations(c: &Ctx, declarations: &Declarations) -> String {
+    let f = Arena::new();
+    let mut defs = Vec::with_capacity(declarations.len());
+    for (index, tag) in declarations.iter_bottom_up() {
+        let symbol = declarations.symbols[index].value;
+        let body = &declarations.expressions[index];
+
+        let def = match tag {
+            DeclarationTag::Value => def_symbol_help(c, &f, symbol, &body.value),
+            DeclarationTag::Function(f_index)
+            | DeclarationTag::Recursive(f_index)
+            | DeclarationTag::TailRecursive(f_index) => {
+                let function_def = &declarations.function_bodies[f_index.index()].value;
+                toplevel_function(c, &f, symbol, function_def, &body.value)
+            }
+            DeclarationTag::Expectation => todo!(),
+            DeclarationTag::ExpectationFx => todo!(),
+            DeclarationTag::Destructure(_) => todo!(),
+            DeclarationTag::MutualRecursion { .. } => todo!(),
+        };
+
+        defs.push(def);
+    }
+
+    f.intersperse(defs, f.hardline().append(f.hardline()))
+        .1
+        .pretty(80)
+        .to_string()
 }
 
 pub fn pretty_print_def(c: &Ctx, d: &Def) -> String {
@@ -40,10 +74,58 @@ fn def<'a>(c: &Ctx, f: &'a Arena<'a>, d: &'a Def) -> DocBuilder<'a, Arena<'a>> {
         annotation: _,
     } = d;
 
-    pattern(c, PPrec::Free, f, &loc_pattern.value)
+    def_help(c, f, &loc_pattern.value, &loc_expr.value)
+}
+
+fn def_symbol_help<'a>(
+    c: &Ctx,
+    f: &'a Arena<'a>,
+    sym: Symbol,
+    body: &'a Expr,
+) -> DocBuilder<'a, Arena<'a>> {
+    pp_sym(c, f, sym)
         .append(f.text(" ="))
         .append(f.line())
-        .append(expr(c, EPrec::Free, f, &loc_expr.value))
+        .append(expr(c, EPrec::Free, f, body))
+        .nest(2)
+        .group()
+}
+
+fn def_help<'a>(
+    c: &Ctx,
+    f: &'a Arena<'a>,
+    pat: &'a Pattern,
+    body: &'a Expr,
+) -> DocBuilder<'a, Arena<'a>> {
+    pattern(c, PPrec::Free, f, pat)
+        .append(f.text(" ="))
+        .append(f.line())
+        .append(expr(c, EPrec::Free, f, body))
+        .nest(2)
+        .group()
+}
+
+fn toplevel_function<'a>(
+    c: &Ctx,
+    f: &'a Arena<'a>,
+    sym: Symbol,
+    function_def: &'a FunctionDef,
+    body: &'a Expr,
+) -> DocBuilder<'a, Arena<'a>> {
+    let FunctionDef { arguments, .. } = function_def;
+
+    let args = arguments
+        .iter()
+        .map(|arg| pattern(c, PPrec::Free, f, &arg.2.value));
+
+    pp_sym(c, f, sym)
+        .append(f.text(" ="))
+        .append(f.line())
+        .append(f.text("\\"))
+        .append(f.intersperse(args, f.text(", ")))
+        .append(f.text("->"))
+        .append(f.line())
+        .append(expr(c, EPrec::Free, f, body))
         .nest(2)
         .group()
 }
@@ -87,11 +169,7 @@ fn expr<'a>(c: &Ctx, p: EPrec, f: &'a Arena<'a>, e: &'a Expr) -> DocBuilder<'a,
                     .append("]")
                     .group(),
             ),
-        Var(sym, _) | AbilityMember(sym, _, _) => f.text(format!(
+        Var(sym, _) | AbilityMember(sym, _, _) => pp_sym(c, f, *sym),
-            "{}.{}",
-            sym.module_string(c.interns),
-            sym.as_str(c.interns),
-        )),
         When {
             loc_cond, branches, ..
         } => maybe_paren!(
@@ -184,6 +262,7 @@ fn expr<'a>(c: &Ctx, p: EPrec, f: &'a Arena<'a>, e: &'a Expr) -> DocBuilder<'a,
         Closure(ClosureData {
             arguments,
             loc_body,
+            name,
             ..
         }) => f
             .text("\\")
@@ -195,7 +274,13 @@ fn expr<'a>(c: &Ctx, p: EPrec, f: &'a Arena<'a>, e: &'a Expr) -> DocBuilder<'a,
                     f.text(", "),
                 ),
             )
-            .append(f.text(" ->"))
+            .append(if c.print_lambda_names {
+                f.text(" -[")
+                    .append(pp_sym(c, f, *name))
+                    .append(f.text("]->"))
+            } else {
+                f.text(" ->")
+            })
             .append(f.line())
             .append(expr(c, Free, f, &loc_body.value))
             .nest(2)
@@ -290,6 +375,18 @@ fn expr<'a>(c: &Ctx, p: EPrec, f: &'a Arena<'a>, e: &'a Expr) -> DocBuilder<'a,
     }
 }
 
+fn pp_sym<'a>(c: &Ctx, f: &'a Arena<'a>, sym: Symbol) -> DocBuilder<'a, Arena<'a>> {
+    if sym.module_id() == c.home {
+        f.text(sym.as_str(c.interns).to_owned())
+    } else {
+        f.text(format!(
+            "{}.{}",
+            sym.module_string(c.interns),
+            sym.as_str(c.interns),
+        ))
+    }
+}
+
 fn branch<'a>(c: &Ctx, f: &'a Arena<'a>, b: &'a WhenBranch) -> DocBuilder<'a, Arena<'a>> {
     let WhenBranch {
         patterns,
@@ -333,11 +430,7 @@ fn pattern<'a>(
         Identifier(sym)
         | AbilityMemberSpecialization {
             specializes: sym, ..
-        } => f.text(format!(
+        } => pp_sym(c, f, *sym),
-            "{}.{}",
-            sym.module_string(c.interns),
-            sym.as_str(c.interns),
-        )),
         AppliedTag {
             tag_name,
             arguments,
@@ -373,12 +466,12 @@ fn pattern<'a>(
                 f.intersperse(
                     destructs.iter().map(|l| &l.value).map(
                         |RecordDestruct { label, typ, .. }| match typ {
-                            roc_can::pattern::DestructType::Required => f.text(label.as_str()),
+                            crate::pattern::DestructType::Required => f.text(label.as_str()),
-                            roc_can::pattern::DestructType::Optional(_, e) => f
+                            crate::pattern::DestructType::Optional(_, e) => f
                                 .text(label.as_str())
                                 .append(f.text(" ? "))
                                 .append(expr(c, EPrec::Free, f, &e.value)),
-                            roc_can::pattern::DestructType::Guard(_, p) => f
+                            crate::pattern::DestructType::Guard(_, p) => f
                                 .text(label.as_str())
                                 .append(f.text(": "))
                                 .append(pattern(c, Free, f, &p.value)),

crates/compiler/can/src/lib.rs

@@ -28,3 +28,5 @@ pub mod string;
 pub mod traverse;
 
 pub use derive::DERIVED_REGION;
+
+pub mod debug;

crates/compiler/constrain/src/expr.rs

@@ -705,7 +705,7 @@ pub fn constrain_expr(
                 expected,
             );
 
-            constraints.exists_many([], [cond_con, continuation_con])
+            constraints.exists_many([*variable], [cond_con, continuation_con])
         }
 
         If {

crates/compiler/gen_llvm/src/llvm/build.rs

@@ -709,7 +709,6 @@ fn float_with_precision<'a, 'ctx, 'env>(
     match float_width {
         FloatWidth::F64 => env.context.f64_type().const_float(value).into(),
         FloatWidth::F32 => env.context.f32_type().const_float(value).into(),
-        FloatWidth::F128 => todo!("F128 is not implemented"),
     }
 }
 
@@ -2586,7 +2585,7 @@ pub fn build_exp_stmt<'a, 'ctx, 'env>(
             condition: cond_symbol,
             region,
             lookups,
-            layouts: _,
+            variables,
             remainder,
         } => {
             let bd = env.builder;
@@ -2621,6 +2620,7 @@ pub fn build_exp_stmt<'a, 'ctx, 'env>(
                             *cond_symbol,
                             *region,
                             lookups,
+                            variables,
                         );
 
                         if let LlvmBackendMode::BinaryDev = env.mode {
@@ -2655,7 +2655,7 @@ pub fn build_exp_stmt<'a, 'ctx, 'env>(
             condition: cond_symbol,
             region,
             lookups,
-            layouts: _,
+            variables,
             remainder,
         } => {
             let bd = env.builder;
@@ -2690,6 +2690,7 @@ pub fn build_exp_stmt<'a, 'ctx, 'env>(
                             *cond_symbol,
                             *region,
                             lookups,
+                            variables,
                         );
 
                         bd.build_unconditional_branch(then_block);
@@ -3036,7 +3037,6 @@ fn build_switch_ir<'a, 'ctx, 'env>(
             let int_type = match float_width {
                 FloatWidth::F32 => env.context.i32_type(),
                 FloatWidth::F64 => env.context.i64_type(),
-                FloatWidth::F128 => env.context.i128_type(),
             };
 
             builder

crates/compiler/gen_llvm/src/llvm/compare.rs

@@ -111,7 +111,6 @@ fn build_eq_builtin<'a, 'ctx, 'env>(
             use FloatWidth::*;
 
             let name = match float_width {
-                F128 => "eq_f128",
                 F64 => "eq_f64",
                 F32 => "eq_f32",
             };
@@ -276,7 +275,6 @@ fn build_neq_builtin<'a, 'ctx, 'env>(
             use FloatWidth::*;
 
             let name = match float_width {
-                F128 => "neq_f128",
                 F64 => "neq_f64",
                 F32 => "neq_f32",
             };

crates/compiler/gen_llvm/src/llvm/convert.rs

@@ -202,7 +202,6 @@ pub fn float_type_from_float_width<'a, 'ctx, 'env>(
     use FloatWidth::*;
 
     match float_width {
-        F128 => todo!("F128 is not implemented"),
         F64 => env.context.f64_type(),
         F32 => env.context.f32_type(),
     }

crates/compiler/gen_llvm/src/llvm/expect.rs

@@ -10,6 +10,7 @@ use inkwell::values::{BasicValueEnum, FunctionValue, IntValue, PointerValue};
 use inkwell::AddressSpace;
 use roc_builtins::bitcode;
 use roc_module::symbol::Symbol;
+use roc_mono::ir::LookupType;
 use roc_mono::layout::{Builtin, Layout, LayoutIds, UnionLayout};
 use roc_region::all::Region;
 
@@ -143,6 +144,21 @@ pub(crate) fn notify_parent_dbg(env: &Env, shared_memory: &SharedMemoryPointer)
     );
 }
 
+// Shape of expect frame:
+//
+//     ===
+//     Fixed-size header
+//     ===
+// /-- ptr_lookup_1  (ptr_size)
+// |   var_lookup_1  (u32)
+// |   ..
+// |   ptr_lookup_n  (ptr_size)
+// |   var_lookup_n  (u32)
+// \-> lookup_val_1  (varsize)
+//     ..
+//     lookup_val_n  (varsize)
+//
+#[allow(clippy::too_many_arguments)]
 pub(crate) fn clone_to_shared_memory<'a, 'ctx, 'env>(
     env: &Env<'a, 'ctx, 'env>,
     scope: &Scope<'a, 'ctx>,
@@ -151,6 +167,7 @@ pub(crate) fn clone_to_shared_memory<'a, 'ctx, 'env>(
     condition: Symbol,
     region: Region,
     lookups: &[Symbol],
+    lookup_variables: &[LookupType],
 ) {
     let original_ptr = shared_memory.0;
 
@@ -160,9 +177,11 @@ pub(crate) fn clone_to_shared_memory<'a, 'ctx, 'env>(
 
     let after_header = offset;
 
-    let space_for_offsets = env
+    let space_for_offsets = env.ptr_int().const_int(
-        .ptr_int()
+        (lookups.len() * env.target_info.ptr_size() + lookups.len() * std::mem::size_of::<u32>())
-        .const_int((lookups.len() * env.target_info.ptr_size()) as _, false);
+            as _,
+        false,
+    );
 
     let mut lookup_starts = bumpalo::collections::Vec::with_capacity_in(lookups.len(), env.arena);
 
@@ -203,14 +222,43 @@ pub(crate) fn clone_to_shared_memory<'a, 'ctx, 'env>(
     {
         let mut offset = after_header;
 
-        for lookup_start in lookup_starts {
+        for (lookup_start, lookup_var) in lookup_starts.into_iter().zip(lookup_variables) {
+            // Store the pointer to the value
+            {
                 build_copy(env, original_ptr, offset, lookup_start.into());
 
                 let ptr_width = env
                     .ptr_int()
                     .const_int(env.target_info.ptr_size() as _, false);
 
-            offset = env.builder.build_int_add(offset, ptr_width, "offset")
+                offset = env.builder.build_int_add(offset, ptr_width, "offset");
+            }
+
+            // Store the specialized variable of the value
+            {
+                let ptr = unsafe {
+                    env.builder
+                        .build_in_bounds_gep(original_ptr, &[offset], "at_current_offset")
+                };
+
+                let u32_ptr = env.context.i32_type().ptr_type(AddressSpace::Generic);
+                let ptr = env
+                    .builder
+                    .build_pointer_cast(ptr, u32_ptr, "cast_ptr_type");
+
+                let var_value = env
+                    .context
+                    .i32_type()
+                    .const_int(lookup_var.index() as _, false);
+
+                env.builder.build_store(ptr, var_value);
+
+                let var_size = env
+                    .ptr_int()
+                    .const_int(std::mem::size_of::<u32>() as _, false);
+
+                offset = env.builder.build_int_add(offset, var_size, "offset");
+            }
         }
     }
 

crates/compiler/gen_llvm/src/llvm/intrinsics.rs

@@ -34,7 +34,6 @@ fn add_float_intrinsic<'ctx, F>(
 
     check!(FloatWidth::F32, ctx.f32_type());
     check!(FloatWidth::F64, ctx.f64_type());
-    // check!(IntWidth::F128, ctx.i128_type());
 }
 
 fn add_int_intrinsic<'ctx, F>(

crates/compiler/gen_llvm/src/llvm/lowlevel.rs

@@ -11,7 +11,7 @@ use roc_builtins::bitcode::{self, FloatWidth, IntWidth};
 use roc_error_macros::internal_error;
 use roc_module::{low_level::LowLevel, symbol::Symbol};
 use roc_mono::{
-    ir::HigherOrderLowLevel,
+    ir::{HigherOrderLowLevel, LookupType},
     layout::{Builtin, LambdaSet, Layout, LayoutIds},
 };
 use roc_target::PtrWidth;
@@ -1120,14 +1120,19 @@ pub(crate) fn run_low_level<'a, 'ctx, 'env>(
             }
         },
         Dbg => {
-            // now what
+            assert_eq!(args.len(), 2);
-            arguments!(condition);
+            let condition = load_symbol(scope, &args[0]);
+            let dbg_spec_var_symbol = args[1];
 
             if env.mode.runs_expects() {
                 let region = unsafe { std::mem::transmute::<_, roc_region::all::Region>(args[0]) };
 
                 let shared_memory = crate::llvm::expect::SharedMemoryPointer::get(env);
 
+                // HACK(dbg-spec-var): the specialized type variable is passed along as a fake symbol
+                let specialized_var =
+                    unsafe { LookupType::from_index(dbg_spec_var_symbol.ident_id().index() as _) };
+
                 crate::llvm::expect::clone_to_shared_memory(
                     env,
                     scope,
@@ -1136,6 +1141,7 @@ pub(crate) fn run_low_level<'a, 'ctx, 'env>(
                     args[0],
                     region,
                     &[args[0]],
+                    &[specialized_var],
                 );
 
                 crate::llvm::expect::notify_parent_dbg(env, &shared_memory);
@@ -2124,13 +2130,6 @@ fn build_float_unary_op<'a, 'ctx, 'env>(
                     "f64_to_f32",
                 ),
                 (FloatWidth::F64, FloatWidth::F64) => arg.into(),
-                (FloatWidth::F128, FloatWidth::F128) => arg.into(),
-                (FloatWidth::F128, _) => {
-                    unimplemented!("I cannot handle F128 with Num.toFrac yet")
-                }
-                (_, FloatWidth::F128) => {
-                    unimplemented!("I cannot handle F128 with Num.toFrac yet")
-                }
             }
         }
         NumCeiling => {

crates/compiler/gen_wasm/src/layout.rs

@@ -21,7 +21,6 @@ pub enum StackMemoryFormat {
     /// Record, Str, List, etc.
     DataStructure,
     Int128,
-    Float128,
     Decimal,
 }
 
@@ -71,11 +70,6 @@ impl WasmLayout {
                 match float_width {
                     F32 => Self::Primitive(ValueType::F32, size),
                     F64 => Self::Primitive(ValueType::F64, size),
-                    F128 => Self::StackMemory {
-                        size,
-                        alignment_bytes,
-                        format: StackMemoryFormat::Float128,
-                    },
                 }
             }
 
@@ -156,7 +150,7 @@ impl CallConv {
         use ValueType::*;
 
         match format {
-            Int128 | Float128 | Decimal => &[I64, I64],
+            Int128 | Decimal => &[I64, I64],
 
             DataStructure => {
                 if size == 0 {
@@ -191,7 +185,7 @@ impl CallConv {
         use StackMemoryFormat::*;
 
         match format {
-            Int128 | Float128 | Decimal => WriteToPointerArg,
+            Int128 | Decimal => WriteToPointerArg,
 
             DataStructure => {
                 if size == 0 {

crates/compiler/gen_wasm/src/low_level.rs

@@ -30,7 +30,6 @@ enum CodeGenNumType {
     F32,     // Supported in Wasm instruction set
     F64,     // Supported in Wasm instruction set
     I128,    // Bytes in memory, needs Zig builtins
-    F128,    // Bytes in memory, needs Zig builtins
     Decimal, // Bytes in memory, needs Zig builtins
 }
 
@@ -66,7 +65,6 @@ impl From<Layout<'_>> for CodeGenNumType {
                 Builtin::Float(float_width) => match float_width {
                     FloatWidth::F32 => F32,
                     FloatWidth::F64 => F64,
-                    FloatWidth::F128 => F128,
                 },
                 Builtin::Decimal => Decimal,
                 _ => not_num_error(),
@@ -91,7 +89,6 @@ impl From<StackMemoryFormat> for CodeGenNumType {
     fn from(format: StackMemoryFormat) -> CodeGenNumType {
         match format {
             StackMemoryFormat::Int128 => CodeGenNumType::I128,
-            StackMemoryFormat::Float128 => CodeGenNumType::F128,
             StackMemoryFormat::Decimal => CodeGenNumType::Decimal,
             StackMemoryFormat::DataStructure => {
                 internal_error!("Tried to perform a Num low-level operation on a data structure")
@@ -804,7 +801,6 @@ impl<'a> LowLevelCall<'a> {
                         self.load_args(backend);
                         backend.code_builder.f64_add()
                     }
-                    FloatWidth::F128 => todo!("Num.add for f128"),
                 },
                 Layout::Builtin(Builtin::Decimal) => {
                     self.load_args_and_call_zig(backend, bitcode::DEC_ADD_OR_PANIC)
@@ -841,7 +837,6 @@ impl<'a> LowLevelCall<'a> {
                         self.load_args(backend);
                         backend.code_builder.f64_add()
                     }
-                    FloatWidth::F128 => todo!("Num.add for f128"),
                 },
                 Layout::Builtin(Builtin::Decimal) => {
                     // TODO: don't panic
@@ -897,7 +892,6 @@ impl<'a> LowLevelCall<'a> {
                         self.load_args(backend);
                         backend.code_builder.f64_sub()
                     }
-                    FloatWidth::F128 => todo!("Num.sub for f128"),
                 },
                 Layout::Builtin(Builtin::Decimal) => {
                     self.load_args_and_call_zig(backend, bitcode::DEC_SUB_OR_PANIC)
@@ -934,7 +928,6 @@ impl<'a> LowLevelCall<'a> {
                         self.load_args(backend);
                         backend.code_builder.f64_sub()
                     }
-                    FloatWidth::F128 => todo!("Num.sub for f128"),
                 },
                 Layout::Builtin(Builtin::Decimal) => {
                     // TODO: don't panic
@@ -988,7 +981,6 @@ impl<'a> LowLevelCall<'a> {
                         self.load_args(backend);
                         backend.code_builder.f64_mul()
                     }
-                    FloatWidth::F128 => todo!("Num.mul for f128"),
                 },
                 Layout::Builtin(Builtin::Decimal) => {
                     self.load_args_and_call_zig(backend, bitcode::DEC_MUL_OR_PANIC)
@@ -1024,7 +1016,6 @@ impl<'a> LowLevelCall<'a> {
                         self.load_args(backend);
                         backend.code_builder.f64_mul()
                     }
-                    FloatWidth::F128 => todo!("Num.mul for f128"),
                 },
                 Layout::Builtin(Builtin::Decimal) => {
                     // TODO: don't panic
@@ -1466,9 +1457,6 @@ impl<'a> LowLevelCall<'a> {
                     Layout::Builtin(Builtin::Float(FloatWidth::F64)) => {
                         backend.code_builder.f64_sqrt()
                     }
-                    Layout::Builtin(Builtin::Float(FloatWidth::F128)) => {
-                        todo!("sqrt for f128")
-                    }
                     _ => panic_ret_type(),
                 }
             }
@@ -2004,8 +1992,6 @@ impl<'a> LowLevelCall<'a> {
 
             StackMemoryFormat::Int128 => Self::eq_num128_bytes(backend, locations),
 
-            StackMemoryFormat::Float128 => todo!("equality for f128"),
-
             StackMemoryFormat::DataStructure => {
                 internal_error!("Data structure equality is handled elsewhere")
             }
@@ -2052,7 +2038,6 @@ impl<'a> LowLevelCall<'a> {
                 FloatWidth::F64 => {
                     self.load_args_and_call_zig(backend, &bitcode::STR_FROM_FLOAT[width]);
                 }
-                FloatWidth::F128 => todo!("F128 to Str"),
             },
             Layout::Builtin(Builtin::Decimal) => {
                 self.load_args_and_call_zig(backend, bitcode::DEC_TO_STR)
@@ -2090,27 +2075,13 @@ fn num_is_finite(backend: &mut WasmBackend<'_>, argument: Symbol) {
                 }
             }
         }
-        StackMemory {
+        StackMemory { format, .. } => {
-            format, location, ..
-        } => {
-            let (local_id, offset) = location.local_and_offset(backend.storage.stack_frame_pointer);
-
             match format {
                 // Integers and fixed-point numbers are always finite. Just return True.
                 StackMemoryFormat::Int128 | StackMemoryFormat::Decimal => {
                     backend.code_builder.i32_const(1)
                 }
 
-                // f128 is not supported anywhere else but it's easy to support it here, so why not...
-                StackMemoryFormat::Float128 => {
-                    backend.code_builder.get_local(local_id);
-                    backend.code_builder.i64_load(Align::Bytes4, offset + 8);
-                    backend.code_builder.i64_const(0x7fff_0000_0000_0000);
-                    backend.code_builder.i64_and();
-                    backend.code_builder.i64_const(0x7fff_0000_0000_0000);
-                    backend.code_builder.i64_ne();
-                }
-
                 StackMemoryFormat::DataStructure => {
                     internal_error!("Tried to perform NumIsFinite on a data structure")
                 }

crates/compiler/gen_wasm/src/storage.rs

@@ -252,7 +252,7 @@ impl<'a> Storage<'a> {
                         .extend_from_slice(CallConv::C.stack_memory_arg_types(size, format));
 
                     let location = match format {
-                        Int128 | Float128 | Decimal => {
+                        Int128 | Decimal => {
                             // passed as two i64's but stored in the stack frame
                             wide_number_args.push(local_index);
                             let loc =

crates/compiler/load_internal/src/file.rs

@@ -140,7 +140,6 @@ struct ModuleCache<'a> {
     found_specializations: MutMap<ModuleId, FoundSpecializationsModule<'a>>,
     late_specializations: MutMap<ModuleId, LateSpecializationsModule<'a>>,
     external_specializations_requested: MutMap<ModuleId, Vec<ExternalSpecializations<'a>>>,
-    expectations: VecMap<ModuleId, Expectations>,
 
     /// Various information
     imports: MutMap<ModuleId, MutSet<ModuleId>>,
@@ -217,7 +216,6 @@ impl Default for ModuleCache<'_> {
             can_problems: Default::default(),
             type_problems: Default::default(),
             sources: Default::default(),
-            expectations: Default::default(),
         }
     }
 }
@@ -437,6 +435,7 @@ fn start_phase<'a>(
                     decls,
                     ident_ids,
                     abilities_store,
+                    expectations,
                 } = typechecked;
 
                 let mut imported_module_thunks = bumpalo::collections::Vec::new_in(arena);
@@ -453,8 +452,8 @@ fn start_phase<'a>(
 
                 let derived_module = SharedDerivedModule::clone(&state.derived_module);
 
-                let build_expects = matches!(state.exec_mode, ExecutionMode::Test)
+                let build_expects =
-                    && state.module_cache.expectations.contains_key(&module_id);
+                    matches!(state.exec_mode, ExecutionMode::Test) && expectations.is_some();
 
                 BuildTask::BuildPendingSpecializations {
                     layout_cache,
@@ -469,6 +468,7 @@ fn start_phase<'a>(
                     // TODO: awful, how can we get rid of the clone?
                     exposed_by_module: state.exposed_types.clone(),
                     derived_module,
+                    expectations,
                     build_expects,
                 }
             }
@@ -490,8 +490,14 @@ fn start_phase<'a>(
                     specializations_we_must_make.extend(derived_synth_specializations)
                 }
 
-                let (mut ident_ids, mut subs, mut procs_base, layout_cache, mut module_timing) =
+                let (
-                    if state.make_specializations_pass.current_pass() == 1
+                    mut ident_ids,
+                    mut subs,
+                    expectations,
+                    mut procs_base,
+                    layout_cache,
+                    mut module_timing,
+                ) = if state.make_specializations_pass.current_pass() == 1
                     && module_id == ModuleId::DERIVED_GEN
                 {
                     // This is the first time the derived module is introduced into the load
@@ -500,6 +506,7 @@ fn start_phase<'a>(
                     (
                         IdentIds::default(),
                         Subs::default(),
+                        None, // no expectations for derived module
                         ProcsBase::default(),
                         LayoutCache::new(state.layout_interner.fork(), state.target_info),
                         ModuleTiming::new(Instant::now()),
@@ -518,6 +525,7 @@ fn start_phase<'a>(
                         layout_cache,
                         module_timing,
                         abilities_store,
+                        expectations,
                     } = found_specializations;
 
                     let our_exposed_types = state
@@ -535,11 +543,19 @@ fn start_phase<'a>(
                         our_exposed_types.exposed_types_storage_subs,
                     );
 
-                        (ident_ids, subs, procs_base, layout_cache, module_timing)
+                    (
+                        ident_ids,
+                        subs,
+                        expectations,
+                        procs_base,
+                        layout_cache,
+                        module_timing,
+                    )
                 } else {
                     let LateSpecializationsModule {
                         ident_ids,
                         subs,
+                        expectations,
                         module_timing,
                         layout_cache,
                         procs_base,
@@ -549,7 +565,14 @@ fn start_phase<'a>(
                         .remove(&module_id)
                         .unwrap();
 
-                        (ident_ids, subs, procs_base, layout_cache, module_timing)
+                    (
+                        ident_ids,
+                        subs,
+                        expectations,
+                        procs_base,
+                        layout_cache,
+                        module_timing,
+                    )
                 };
 
                 if module_id == ModuleId::DERIVED_GEN {
@@ -581,6 +604,7 @@ fn start_phase<'a>(
                     // TODO: awful, how can we get rid of the clone?
                     exposed_by_module: state.exposed_types.clone(),
                     derived_module,
+                    expectations,
                 }
             }
         }
@@ -681,6 +705,7 @@ pub struct TypeCheckedModule<'a> {
     pub decls: Declarations,
     pub ident_ids: IdentIds,
     pub abilities_store: AbilitiesStore,
+    pub expectations: Option<Expectations>,
 }
 
 #[derive(Debug)]
@@ -691,6 +716,7 @@ struct FoundSpecializationsModule<'a> {
     subs: Subs,
     module_timing: ModuleTiming,
     abilities_store: AbilitiesStore,
+    expectations: Option<Expectations>,
 }
 
 #[derive(Debug)]
@@ -700,6 +726,7 @@ struct LateSpecializationsModule<'a> {
     module_timing: ModuleTiming,
     layout_cache: LayoutCache<'a>,
     procs_base: ProcsBase<'a>,
+    expectations: Option<Expectations>,
 }
 
 #[derive(Debug, Default)]
@@ -833,6 +860,7 @@ enum Msg<'a> {
         module_timing: ModuleTiming,
         abilities_store: AbilitiesStore,
         toplevel_expects: ToplevelExpects,
+        expectations: Option<Expectations>,
     },
     MadeSpecializations {
         module_id: ModuleId,
@@ -844,6 +872,7 @@ enum Msg<'a> {
         update_mode_ids: UpdateModeIds,
         module_timing: ModuleTiming,
         subs: Subs,
+        expectations: Option<Expectations>,
     },
 
     /// The task is to only typecheck AND monomorphize modules
@@ -854,6 +883,7 @@ enum Msg<'a> {
         /// DO NOT use the one on state; that is left in an empty state after specialization is complete!
         layout_interner: STLayoutInterner<'a>,
         exposed_to_host: ExposedToHost,
+        module_expectations: VecMap<ModuleId, Expectations>,
     },
 
     FailedToParse(FileError<'a, SyntaxError<'a>>),
@@ -1150,6 +1180,7 @@ enum BuildTask<'a> {
         exposed_by_module: ExposedByModule,
         abilities_store: AbilitiesStore,
         derived_module: SharedDerivedModule,
+        expectations: Option<Expectations>,
         build_expects: bool,
     },
     MakeSpecializations {
@@ -1163,6 +1194,7 @@ enum BuildTask<'a> {
         exposed_by_module: ExposedByModule,
         world_abilities: WorldAbilities,
         derived_module: SharedDerivedModule,
+        expectations: Option<Expectations>,
     },
 }
 
@@ -1671,6 +1703,7 @@ fn state_thread_step<'a>(
                     subs,
                     layout_interner,
                     exposed_to_host,
+                    module_expectations,
                 } => {
                     // We're done! There should be no more messages pending.
                     debug_assert!(msg_rx.is_empty());
@@ -1681,6 +1714,7 @@ fn state_thread_step<'a>(
                         subs,
                         layout_interner,
                         exposed_to_host,
+                        module_expectations,
                     )?;
 
                     Ok(ControlFlow::Break(LoadResult::Monomorphized(monomorphized)))
@@ -2636,23 +2670,20 @@ fn update<'a>(
                     .expect("root or this module is not yet known - that's a bug!")
             };
 
-            if should_include_expects {
+            let opt_expectations = if should_include_expects {
                 let (path, _) = state.module_cache.sources.get(&module_id).unwrap();
 
-                let expectations = Expectations {
+                Some(Expectations {
                     expectations: loc_expects,
                     dbgs: loc_dbgs,
                     subs: solved_subs.clone().into_inner(),
                     path: path.to_owned(),
                     ident_ids: ident_ids.clone(),
+                })
+            } else {
+                None
             };
 
-                state
-                    .module_cache
-                    .expectations
-                    .insert(module_id, expectations);
-            }
-
             let work = state.dependencies.notify(module_id, Phase::SolveTypes);
 
             // if there is a platform, the `platform` module provides host-exposed,
@@ -2764,6 +2795,7 @@ fn update<'a>(
                         decls,
                         ident_ids,
                         abilities_store,
+                        expectations: opt_expectations,
                     };
 
                     state
@@ -2803,6 +2835,7 @@ fn update<'a>(
             module_timing,
             abilities_store,
             toplevel_expects,
+            expectations,
         } => {
             log!("found specializations for {:?}", module_id);
 
@@ -2825,6 +2858,7 @@ fn update<'a>(
                 subs,
                 module_timing,
                 abilities_store,
+                expectations,
             };
 
             state
@@ -2850,6 +2884,7 @@ fn update<'a>(
             external_specializations_requested,
             module_timing,
             layout_cache,
+            expectations,
             ..
         } => {
             debug_assert!(
@@ -2871,6 +2906,7 @@ fn update<'a>(
                     subs,
                     layout_cache,
                     procs_base,
+                    expectations,
                 },
             );
 
@@ -2928,6 +2964,9 @@ fn update<'a>(
                         );
                     }
 
+                    let mut module_expectations =
+                        VecMap::with_capacity(state.module_cache.module_names.len());
+
                     // Flush late-specialization module information to the top-level of the state
                     // where it will be visible to others, since we don't need late specialization
                     // anymore.
@@ -2939,6 +2978,7 @@ fn update<'a>(
                             module_timing,
                             layout_cache: _layout_cache,
                             procs_base: _,
+                            expectations,
                         },
                     ) in state.module_cache.late_specializations.drain()
                     {
@@ -2947,6 +2987,9 @@ fn update<'a>(
                             state.root_subs = Some(subs);
                         }
                         state.timings.insert(module_id, module_timing);
+                        if let Some(expectations) = expectations {
+                            module_expectations.insert(module_id, expectations);
+                        }
 
                         #[cfg(debug_assertions)]
                         {
@@ -3009,6 +3052,7 @@ fn update<'a>(
                             subs,
                             layout_interner,
                             exposed_to_host: state.exposed_to_host.clone(),
+                            module_expectations,
                         })
                         .map_err(|_| LoadingProblem::MsgChannelDied)?;
 
@@ -3146,6 +3190,7 @@ fn finish_specialization<'a>(
     subs: Subs,
     layout_interner: STLayoutInterner<'a>,
     exposed_to_host: ExposedToHost,
+    module_expectations: VecMap<ModuleId, Expectations>,
 ) -> Result<MonomorphizedModule<'a>, LoadingProblem<'a>> {
     if false {
         println!(
@@ -3186,7 +3231,6 @@ fn finish_specialization<'a>(
     } = state;
 
     let ModuleCache {
-        expectations,
         type_problems,
         can_problems,
         sources,
@@ -3277,7 +3321,7 @@ fn finish_specialization<'a>(
         can_problems,
         type_problems,
         output_path,
-        expectations,
+        expectations: module_expectations,
         exposed_to_host,
         module_id: state.root_id,
         subs,
@@ -5395,6 +5439,7 @@ fn make_specializations<'a>(
     world_abilities: WorldAbilities,
     exposed_by_module: &ExposedByModule,
     derived_module: SharedDerivedModule,
+    mut expectations: Option<Expectations>,
 ) -> Msg<'a> {
     let make_specializations_start = Instant::now();
     let mut update_mode_ids = UpdateModeIds::new();
@@ -5402,6 +5447,7 @@ fn make_specializations<'a>(
     let mut mono_env = roc_mono::ir::Env {
         arena,
         subs: &mut subs,
+        expectation_subs: expectations.as_mut().map(|e| &mut e.subs),
         home,
         ident_ids: &mut ident_ids,
         target_info,
@@ -5453,6 +5499,7 @@ fn make_specializations<'a>(
         procedures,
         update_mode_ids,
         subs,
+        expectations,
         external_specializations_requested,
         module_timing,
     }
@@ -5472,6 +5519,7 @@ fn build_pending_specializations<'a>(
     exposed_by_module: &ExposedByModule,
     abilities_store: AbilitiesStore,
     derived_module: SharedDerivedModule,
+    mut expectations: Option<Expectations>,
     build_expects: bool,
 ) -> Msg<'a> {
     let find_specializations_start = Instant::now();
@@ -5492,6 +5540,7 @@ fn build_pending_specializations<'a>(
     let mut mono_env = roc_mono::ir::Env {
         arena,
         subs: &mut subs,
+        expectation_subs: expectations.as_mut().map(|e| &mut e.subs),
         home,
         ident_ids: &mut ident_ids,
         target_info,
@@ -5881,6 +5930,7 @@ fn build_pending_specializations<'a>(
         module_timing,
         abilities_store,
         toplevel_expects,
+        expectations,
     }
 }
 
@@ -5922,6 +5972,8 @@ fn load_derived_partial_procs<'a>(
         let mut mono_env = roc_mono::ir::Env {
             arena,
             subs,
+            // There are no derived expectations.
+            expectation_subs: None,
             home,
             ident_ids,
             target_info,
@@ -6081,6 +6133,7 @@ fn run_task<'a>(
             abilities_store,
             exposed_by_module,
             derived_module,
+            expectations,
             build_expects,
         } => Ok(build_pending_specializations(
             arena,
@@ -6096,6 +6149,7 @@ fn run_task<'a>(
             &exposed_by_module,
             abilities_store,
             derived_module,
+            expectations,
             build_expects,
         )),
         MakeSpecializations {
@@ -6109,6 +6163,7 @@ fn run_task<'a>(
             world_abilities,
             exposed_by_module,
             derived_module,
+            expectations,
         } => Ok(make_specializations(
             arena,
             module_id,
@@ -6122,6 +6177,7 @@ fn run_task<'a>(
             world_abilities,
             &exposed_by_module,
             derived_module,
+            expectations,
         )),
     }?;
 

crates/compiler/module/src/symbol.rs

@@ -594,6 +594,13 @@ impl IdentId {
     pub const fn index(self) -> usize {
         self.0 as usize
     }
+
+    /// # Safety
+    ///
+    /// The index is not guaranteed to know to exist.
+    pub unsafe fn from_index(index: u32) -> Self {
+        Self(index)
+    }
 }
 
 /// Stores a mapping between Ident and IdentId.

crates/compiler/mono/src/borrow.rs

@@ -162,9 +162,15 @@ impl<'a> DeclarationToIndex<'a> {
                 }
             }
         }
+
+        let similar = self
+            .elements
+            .iter()
+            .filter_map(|((s, lay), _)| if *s == needle_symbol { Some(lay) } else { None })
+            .collect::<std::vec::Vec<_>>();
         unreachable!(
-            "symbol/layout {:?} {:#?} combo must be in DeclarationToIndex",
+            "symbol/layout {:?} {:#?} combo must be in DeclarationToIndex\nHowever {} similar layouts were found:\n{:#?}",
-            needle_symbol, needle_layout
+            needle_symbol, needle_layout, similar.len(), similar
         )
     }
 }
@@ -942,7 +948,7 @@ pub fn lowlevel_borrow_signature(arena: &Bump, op: LowLevel) -> &[bool] {
 
         ListIsUnique => arena.alloc_slice_copy(&[borrowed]),
 
-        Dbg => arena.alloc_slice_copy(&[borrowed]),
+        Dbg => arena.alloc_slice_copy(&[borrowed, /* dbg-spec-var */ irrelevant]),
 
         BoxExpr | UnboxExpr => {
             unreachable!("These lowlevel operations are turned into mono Expr's")

crates/compiler/mono/src/debug/checker.rs

@@ -309,14 +309,14 @@ impl<'a, 'r> Ctx<'a, 'r> {
                 condition,
                 region: _,
                 lookups,
-                layouts,
+                variables: _,
                 remainder,
             }
             | &Stmt::ExpectFx {
                 condition,
                 region: _,
                 lookups,
-                layouts,
+                variables: _,
                 remainder,
             } => {
                 self.check_sym_layout(
@@ -324,8 +324,8 @@ impl<'a, 'r> Ctx<'a, 'r> {
                     Layout::Builtin(Builtin::Bool),
                     UseKind::ExpectCond,
                 );
-                for (sym, lay) in lookups.iter().zip(layouts) {
+                for sym in lookups.iter() {
-                    self.check_sym_layout(*sym, *lay, UseKind::ExpectLookup);
+                    self.check_sym_exists(*sym);
                 }
                 self.check_stmt(remainder);
             }

crates/compiler/mono/src/inc_dec.rs

@@ -555,7 +555,13 @@ impl<'a, 'i> Context<'a, 'i> {
         match &call_type {
             LowLevel { op, .. } => {
                 let ps = crate::borrow::lowlevel_borrow_signature(self.arena, *op);
-                let b = self.add_dec_after_lowlevel(arguments, ps, b, b_live_vars);
+                let b = match op {
+                    roc_module::low_level::LowLevel::Dbg => {
+                        // NB(dbg-spec-var) second var is the Variable
+                        self.add_dec_after_lowlevel(&arguments[..1], ps, b, b_live_vars)
+                    }
+                    _ => self.add_dec_after_lowlevel(arguments, ps, b, b_live_vars),
+                };
 
                 let v = Expr::Call(crate::ir::Call {
                     call_type,
@@ -1199,7 +1205,7 @@ impl<'a, 'i> Context<'a, 'i> {
                 condition,
                 region,
                 lookups,
-                layouts,
+                variables,
             } => {
                 let (b, mut b_live_vars) = self.visit_stmt(codegen, remainder);
 
@@ -1207,7 +1213,7 @@ impl<'a, 'i> Context<'a, 'i> {
                     condition: *condition,
                     region: *region,
                     lookups,
-                    layouts,
+                    variables,
                     remainder: b,
                 });
 
@@ -1223,7 +1229,7 @@ impl<'a, 'i> Context<'a, 'i> {
                 condition,
                 region,
                 lookups,
-                layouts,
+                variables,
             } => {
                 let (b, mut b_live_vars) = self.visit_stmt(codegen, remainder);
 
@@ -1231,7 +1237,7 @@ impl<'a, 'i> Context<'a, 'i> {
                     condition: *condition,
                     region: *region,
                     lookups,
-                    layouts,
+                    variables,
                     remainder: b,
                 });
 

crates/compiler/mono/src/ir.rs

@@ -27,14 +27,14 @@ use roc_late_solve::storage::{ExternalModuleStorage, ExternalModuleStorageSnapsh
 use roc_late_solve::{resolve_ability_specialization, AbilitiesView, Resolved, UnificationFailed};
 use roc_module::ident::{ForeignSymbol, Lowercase, TagName};
 use roc_module::low_level::LowLevel;
-use roc_module::symbol::{IdentIds, ModuleId, Symbol};
+use roc_module::symbol::{IdentId, IdentIds, ModuleId, Symbol};
 use roc_problem::can::{RuntimeError, ShadowKind};
 use roc_region::all::{Loc, Region};
 use roc_std::RocDec;
 use roc_target::TargetInfo;
 use roc_types::subs::{
-    instantiate_rigids, Content, ExhaustiveMark, FlatType, RedundantMark, StorageSubs, Subs,
+    instantiate_rigids, storage_copy_var_to, Content, ExhaustiveMark, FlatType, RedundantMark,
-    Variable, VariableSubsSlice,
+    StorageSubs, Subs, Variable, VariableSubsSlice,
 };
 use std::collections::HashMap;
 use ven_pretty::{BoxAllocator, DocAllocator, DocBuilder};
@@ -1465,6 +1465,9 @@ impl<'a> Specializations<'a> {
 pub struct Env<'a, 'i> {
     pub arena: &'a Bump,
     pub subs: &'i mut Subs,
+    /// [Subs] to write specialized variables of lookups in expects.
+    /// [None] if this module doesn't produce any expects.
+    pub expectation_subs: Option<&'i mut Subs>,
     pub home: ModuleId,
     pub ident_ids: &'i mut IdentIds,
     pub target_info: TargetInfo,
@@ -1601,6 +1604,9 @@ pub fn cond<'a>(
 
 pub type Stores<'a> = &'a [(Symbol, Layout<'a>, Expr<'a>)];
 
+/// The specialized type of a lookup. Represented as a type-variable.
+pub type LookupType = Variable;
+
 #[derive(Clone, Debug, PartialEq)]
 pub enum Stmt<'a> {
     Let(Symbol, Expr<'a>, Layout<'a>, &'a Stmt<'a>),
@@ -1622,7 +1628,7 @@ pub enum Stmt<'a> {
         condition: Symbol,
         region: Region,
         lookups: &'a [Symbol],
-        layouts: &'a [Layout<'a>],
+        variables: &'a [LookupType],
         /// what happens after the expect
         remainder: &'a Stmt<'a>,
     },
@@ -1630,7 +1636,7 @@ pub enum Stmt<'a> {
         condition: Symbol,
         region: Region,
         lookups: &'a [Symbol],
-        layouts: &'a [Layout<'a>],
+        variables: &'a [LookupType],
         /// what happens after the expect
         remainder: &'a Stmt<'a>,
     },
@@ -6570,13 +6576,14 @@ pub fn from_can<'a>(
             let cond_symbol = env.unique_symbol();
 
             let mut lookups = Vec::with_capacity_in(lookups_in_cond.len(), env.arena);
-            let mut layouts = Vec::with_capacity_in(lookups_in_cond.len(), env.arena);
+            let mut lookup_variables = Vec::with_capacity_in(lookups_in_cond.len(), env.arena);
+            let mut specialized_variables = Vec::with_capacity_in(lookups_in_cond.len(), env.arena);
 
             for ExpectLookup {
                 symbol,
                 var,
                 ability_info,
-            } in lookups_in_cond
+            } in lookups_in_cond.iter().copied()
             {
                 let symbol = match ability_info {
                     Some(specialization_id) => late_resolve_ability_specialization(
@@ -6587,20 +6594,28 @@ pub fn from_can<'a>(
                     ),
                     None => symbol,
                 };
-                let res_layout = layout_cache.from_var(env.arena, var, env.subs);
+
-                let layout = return_on_layout_error!(env, res_layout, "Expect");
+                let expectation_subs = env
-                if !matches!(layout, Layout::LambdaSet(..)) {
+                    .expectation_subs
+                    .as_deref_mut()
+                    .expect("if expects are compiled, their subs should be available");
+                let spec_var = expectation_subs.fresh_unnamed_flex_var();
+
+                if !env.subs.is_function(var) {
                     // Exclude functions from lookups
                     lookups.push(symbol);
-                    layouts.push(layout);
+                    lookup_variables.push(var);
+                    specialized_variables.push(spec_var);
                 }
             }
 
+            let specialized_variables = specialized_variables.into_bump_slice();
+
             let mut stmt = Stmt::Expect {
                 condition: cond_symbol,
                 region: loc_condition.region,
                 lookups: lookups.into_bump_slice(),
-                layouts: layouts.into_bump_slice(),
+                variables: specialized_variables,
                 remainder: env.arena.alloc(rest),
             };
 
@@ -6614,6 +6629,10 @@ pub fn from_can<'a>(
                 env.arena.alloc(stmt),
             );
 
+            // Now that the condition has been specialized, export the specialized types of our
+            // lookups into the expectation subs.
+            store_specialized_expectation_lookups(env, lookup_variables, specialized_variables);
+
             stmt
         }
 
@@ -6626,13 +6645,14 @@ pub fn from_can<'a>(
             let cond_symbol = env.unique_symbol();
 
             let mut lookups = Vec::with_capacity_in(lookups_in_cond.len(), env.arena);
-            let mut layouts = Vec::with_capacity_in(lookups_in_cond.len(), env.arena);
+            let mut lookup_variables = Vec::with_capacity_in(lookups_in_cond.len(), env.arena);
+            let mut specialized_variables = Vec::with_capacity_in(lookups_in_cond.len(), env.arena);
 
             for ExpectLookup {
                 symbol,
                 var,
                 ability_info,
-            } in lookups_in_cond
+            } in lookups_in_cond.iter().copied()
             {
                 let symbol = match ability_info {
                     Some(specialization_id) => late_resolve_ability_specialization(
@@ -6643,20 +6663,28 @@ pub fn from_can<'a>(
                     ),
                     None => symbol,
                 };
-                let res_layout = layout_cache.from_var(env.arena, var, env.subs);
+
-                let layout = return_on_layout_error!(env, res_layout, "Expect");
+                let expectation_subs = env
-                if !matches!(layout, Layout::LambdaSet(..)) {
+                    .expectation_subs
+                    .as_deref_mut()
+                    .expect("if expects are compiled, their subs should be available");
+                let spec_var = expectation_subs.fresh_unnamed_flex_var();
+
+                if !env.subs.is_function(var) {
                     // Exclude functions from lookups
                     lookups.push(symbol);
-                    layouts.push(layout);
+                    lookup_variables.push(var);
+                    specialized_variables.push(spec_var);
                 }
             }
 
+            let specialized_variables = specialized_variables.into_bump_slice();
+
             let mut stmt = Stmt::ExpectFx {
                 condition: cond_symbol,
                 region: loc_condition.region,
                 lookups: lookups.into_bump_slice(),
-                layouts: layouts.into_bump_slice(),
+                variables: specialized_variables,
                 remainder: env.arena.alloc(rest),
             };
 
@@ -6670,6 +6698,8 @@ pub fn from_can<'a>(
                 env.arena.alloc(stmt),
             );
 
+            store_specialized_expectation_lookups(env, lookup_variables, specialized_variables);
+
             stmt
         }
 
@@ -6681,12 +6711,23 @@ pub fn from_can<'a>(
         } => {
             let rest = from_can(env, variable, loc_continuation.value, procs, layout_cache);
 
+            let spec_var = env
+                .expectation_subs
+                .as_mut()
+                .unwrap()
+                .fresh_unnamed_flex_var();
+            // HACK(dbg-spec-var): pass the specialized type variable along injected into a fake symbol
+            let dbg_spec_var_symbol = Symbol::new(ModuleId::ATTR, unsafe {
+                IdentId::from_index(spec_var.index())
+            });
+
+            // TODO: need to store the specialized variable of this dbg in the expectation_subs
             let call = crate::ir::Call {
                 call_type: CallType::LowLevel {
                     op: LowLevel::Dbg,
                     update_mode: env.next_update_mode_id(),
                 },
-                arguments: env.arena.alloc([dbg_symbol]),
+                arguments: env.arena.alloc([dbg_symbol, dbg_spec_var_symbol]),
             };
 
             let dbg_layout = layout_cache
@@ -6714,6 +6755,10 @@ pub fn from_can<'a>(
                 );
             }
 
+            // Now that the dbg value has been specialized, export its specialized type into the
+            // expectations subs.
+            store_specialized_expectation_lookups(env, [variable], &[spec_var]);
+
             stmt
         }
 
@@ -6752,6 +6797,21 @@ pub fn from_can<'a>(
     }
 }
 
+fn store_specialized_expectation_lookups(
+    env: &mut Env,
+    lookup_variables: impl IntoIterator<Item = Variable>,
+    specialized_variables: &[Variable],
+) {
+    let subs = &env.subs;
+    let expectation_subs = env.expectation_subs.as_deref_mut().unwrap();
+    for (lookup_var, stored_var) in lookup_variables.into_iter().zip(specialized_variables) {
+        let stored_specialized_var =
+            storage_copy_var_to(&mut Default::default(), subs, expectation_subs, lookup_var);
+        let stored_specialized_desc = expectation_subs.get(stored_specialized_var);
+        expectation_subs.union(*stored_var, stored_specialized_var, stored_specialized_desc);
+    }
+}
+
 fn to_opt_branches<'a>(
     env: &mut Env<'a, '_>,
     procs: &mut Procs<'a>,
@@ -7082,7 +7142,7 @@ fn substitute_in_stmt_help<'a>(
             condition,
             region,
             lookups,
-            layouts,
+            variables,
             remainder,
         } => {
             let new_remainder =
@@ -7097,7 +7157,7 @@ fn substitute_in_stmt_help<'a>(
                 condition: substitute(subs, *condition).unwrap_or(*condition),
                 region: *region,
                 lookups: new_lookups.into_bump_slice(),
-                layouts,
+                variables,
                 remainder: new_remainder,
             };
 
@@ -7108,7 +7168,7 @@ fn substitute_in_stmt_help<'a>(
             condition,
             region,
             lookups,
-            layouts,
+            variables,
             remainder,
         } => {
             let new_remainder =
@@ -7123,7 +7183,7 @@ fn substitute_in_stmt_help<'a>(
                 condition: substitute(subs, *condition).unwrap_or(*condition),
                 region: *region,
                 lookups: new_lookups.into_bump_slice(),
-                layouts,
+                variables,
                 remainder: new_remainder,
             };
 
@@ -8234,7 +8294,46 @@ fn specialize_symbol<'a>(
                         Err(e) => return_on_layout_error_help!(env, e, "specialize_symbol"),
                     };
 
-                    if procs.is_imported_module_thunk(original) {
+                    match raw {
+                        RawFunctionLayout::Function(_, lambda_set, _)
+                            if !procs.is_imported_module_thunk(original) =>
+                        {
+                            let lambda_name =
+                                find_lambda_name(env, layout_cache, lambda_set, original, &[]);
+
+                            debug_assert!(
+                                lambda_name.no_captures(),
+                                "imported functions are top-level and should never capture"
+                            );
+
+                            let function_ptr_layout = ProcLayout::from_raw(
+                                env.arena,
+                                &layout_cache.interner,
+                                raw,
+                                lambda_name.captures_niche(),
+                            );
+                            procs.insert_passed_by_name(
+                                env,
+                                arg_var,
+                                lambda_name,
+                                function_ptr_layout,
+                                layout_cache,
+                            );
+
+                            construct_closure_data(
+                                env,
+                                procs,
+                                layout_cache,
+                                lambda_set,
+                                lambda_name,
+                                &[],
+                                assign_to,
+                                env.arena.alloc(result),
+                            )
+                        }
+                        _ => {
+                            // This is an imported ZAT that returns either a value, or the closure
+                            // data for a lambda set.
                             let layout = match raw {
                                 RawFunctionLayout::ZeroArgumentThunk(layout) => layout,
                                 RawFunctionLayout::Function(_, lambda_set, _) => {
@@ -8259,24 +8358,7 @@ fn specialize_symbol<'a>(
                             );
 
                             force_thunk(env, original, layout, assign_to, env.arena.alloc(result))
-                    } else {
+                        }
-                        // Imported symbol, so it must have no captures niche (since
-                        // top-levels can't capture)
-                        let top_level = ProcLayout::from_raw(
-                            env.arena,
-                            &layout_cache.interner,
-                            raw,
-                            CapturesNiche::no_niche(),
-                        );
-                        procs.insert_passed_by_name(
-                            env,
-                            arg_var,
-                            LambdaName::no_niche(original),
-                            top_level,
-                            layout_cache,
-                        );
-
-                        let_empty_struct(assign_to, env.arena.alloc(result))
                     }
                 }
 

crates/compiler/mono/src/layout.rs

@@ -2890,7 +2890,6 @@ impl<'a> Builtin<'a> {
                 use FloatWidth::*;
 
                 match float_width {
-                    F128 => alloc.text("Float128"),
                     F64 => alloc.text("Float64"),
                     F32 => alloc.text("Float32"),
                 }

crates/compiler/mono/src/reset_reuse.rs

@@ -195,7 +195,7 @@ fn function_s<'a, 'i>(
             condition,
             region,
             lookups,
-            layouts,
+            variables,
             remainder,
         } => {
             let continuation: &Stmt = remainder;
@@ -208,7 +208,7 @@ fn function_s<'a, 'i>(
                     condition: *condition,
                     region: *region,
                     lookups,
-                    layouts,
+                    variables,
                     remainder: new_continuation,
                 };
 
@@ -220,7 +220,7 @@ fn function_s<'a, 'i>(
             condition,
             region,
             lookups,
-            layouts,
+            variables,
             remainder,
         } => {
             let continuation: &Stmt = remainder;
@@ -233,7 +233,7 @@ fn function_s<'a, 'i>(
                     condition: *condition,
                     region: *region,
                     lookups,
-                    layouts,
+                    variables,
                     remainder: new_continuation,
                 };
 
@@ -442,7 +442,7 @@ fn function_d_main<'a, 'i>(
             condition,
             region,
             lookups,
-            layouts,
+            variables,
             remainder,
         } => {
             let (b, found) = function_d_main(env, x, c, remainder);
@@ -452,7 +452,7 @@ fn function_d_main<'a, 'i>(
                     condition: *condition,
                     region: *region,
                     lookups,
-                    layouts,
+                    variables,
                     remainder: b,
                 };
 
@@ -464,7 +464,7 @@ fn function_d_main<'a, 'i>(
                     condition: *condition,
                     region: *region,
                     lookups,
-                    layouts,
+                    variables,
                     remainder: b,
                 };
 
@@ -475,7 +475,7 @@ fn function_d_main<'a, 'i>(
             condition,
             region,
             lookups,
-            layouts,
+            variables,
             remainder,
         } => {
             let (b, found) = function_d_main(env, x, c, remainder);
@@ -485,7 +485,7 @@ fn function_d_main<'a, 'i>(
                     condition: *condition,
                     region: *region,
                     lookups,
-                    layouts,
+                    variables,
                     remainder: b,
                 };
 
@@ -497,7 +497,7 @@ fn function_d_main<'a, 'i>(
                     condition: *condition,
                     region: *region,
                     lookups,
-                    layouts,
+                    variables,
                     remainder: b,
                 };
 
@@ -660,7 +660,7 @@ fn function_r<'a, 'i>(env: &mut Env<'a, 'i>, stmt: &'a Stmt<'a>) -> &'a Stmt<'a>
             condition,
             region,
             lookups,
-            layouts,
+            variables,
             remainder,
         } => {
             let b = function_r(env, remainder);
@@ -669,7 +669,7 @@ fn function_r<'a, 'i>(env: &mut Env<'a, 'i>, stmt: &'a Stmt<'a>) -> &'a Stmt<'a>
                 condition: *condition,
                 region: *region,
                 lookups,
-                layouts,
+                variables,
                 remainder: b,
             };
 
@@ -680,7 +680,7 @@ fn function_r<'a, 'i>(env: &mut Env<'a, 'i>, stmt: &'a Stmt<'a>) -> &'a Stmt<'a>
             condition,
             region,
             lookups,
-            layouts,
+            variables,
             remainder,
         } => {
             let b = function_r(env, remainder);
@@ -689,7 +689,7 @@ fn function_r<'a, 'i>(env: &mut Env<'a, 'i>, stmt: &'a Stmt<'a>) -> &'a Stmt<'a>
                 condition: *condition,
                 region: *region,
                 lookups,
-                layouts,
+                variables,
                 remainder: b,
             };
 

crates/compiler/mono/src/tail_recursion.rs

@@ -253,7 +253,7 @@ fn insert_jumps<'a>(
             condition,
             region,
             lookups,
-            layouts,
+            variables,
             remainder,
         } => match insert_jumps(
             arena,
@@ -267,7 +267,7 @@ fn insert_jumps<'a>(
                 condition: *condition,
                 region: *region,
                 lookups,
-                layouts,
+                variables,
                 remainder: cont,
             })),
             None => None,
@@ -277,7 +277,7 @@ fn insert_jumps<'a>(
             condition,
             region,
             lookups,
-            layouts,
+            variables,
             remainder,
         } => match insert_jumps(
             arena,
@@ -291,7 +291,7 @@ fn insert_jumps<'a>(
                 condition: *condition,
                 region: *region,
                 lookups,
-                layouts,
+                variables,
                 remainder: cont,
             })),
             None => None,

crates/compiler/solve/tests/solve_expr.rs

@@ -262,6 +262,7 @@ mod solve_expr {
 
     #[derive(Default)]
     struct InferOptions {
+        print_can_decls: bool,
         print_only_under_alias: bool,
         allow_errors: bool,
     }
@@ -302,7 +303,20 @@ mod solve_expr {
         let queries = parse_queries(&src);
         assert!(!queries.is_empty(), "No queries provided!");
 
-        let mut solved_queries = Vec::with_capacity(queries.len());
+        let mut output_parts = Vec::with_capacity(queries.len() + 2);
+
+        if options.print_can_decls {
+            use roc_can::debug::{pretty_print_declarations, PPCtx};
+            let ctx = PPCtx {
+                home,
+                interns: &interns,
+                print_lambda_names: true,
+            };
+            let pretty_decls = pretty_print_declarations(&ctx, &decls);
+            output_parts.push(pretty_decls);
+            output_parts.push("\n".to_owned());
+        }
+
         for TypeQuery(region) in queries.into_iter() {
             let start = region.start().offset;
             let end = region.end().offset;
@@ -340,12 +354,12 @@ mod solve_expr {
                     }
                 };
 
-            solved_queries.push(elaborated);
+            output_parts.push(elaborated);
         }
 
-        let pretty_solved_queries = solved_queries.join("\n");
+        let pretty_output = output_parts.join("\n");
 
-        expected(&pretty_solved_queries);
+        expected(&pretty_output);
     }
 
     macro_rules! infer_queries {
@@ -6720,9 +6734,9 @@ mod solve_expr {
                 "#
             ),
             @r#"
-            A#id(5) : {} -[[id(5)]]-> ({} -[[8(8)]]-> {})
+            A#id(5) : {} -[[id(5)]]-> ({} -[[8]]-> {})
             Id#id(3) : a -[[] + a:id(3):1]-> ({} -[[] + a:id(3):2]-> a) | a has Id
-            alias : {} -[[id(5)]]-> ({} -[[8(8)]]-> {})
+            alias : {} -[[id(5)]]-> ({} -[[8]]-> {})
             "#
             print_only_under_alias: true
         )
@@ -6751,8 +6765,8 @@ mod solve_expr {
                 "#
             ),
             @r#"
-            A#id(5) : {} -[[id(5)]]-> ({} -[[8(8)]]-> {})
+            A#id(5) : {} -[[id(5)]]-> ({} -[[8]]-> {})
-            it : {} -[[8(8)]]-> {}
+            it : {} -[[8]]-> {}
             "#
             print_only_under_alias: true
         )
@@ -6782,8 +6796,8 @@ mod solve_expr {
                 "#
             ),
             @r#"
-            A#id(5) : {} -[[id(5)]]-> ({} -[[8(8)]]-> {})
+            A#id(5) : {} -[[id(5)]]-> ({} -[[8]]-> {})
-            A#id(5) : {} -[[id(5)]]-> ({} -[[8(8)]]-> {})
+            A#id(5) : {} -[[id(5)]]-> ({} -[[8]]-> {})
             "#
             print_only_under_alias: true
         )
@@ -6903,7 +6917,7 @@ mod solve_expr {
                 #^^^^^^^^^^^^^^^^^^^^^^{-1}
                 "#
             ),
-            @r#"[\{} -> {}, \{} -> {}] : List ({}* -[[1(1), 2(2)]]-> {})"#
+            @r###"[\{} -> {}, \{} -> {}] : List ({}* -[[1, 2]]-> {})"###
         )
     }
 
@@ -7078,7 +7092,7 @@ mod solve_expr {
                 #^^^{-1}
                 "#
             ),
-            @r#"fun : {} -[[thunk(9) (({} -[[15(15)]]-> { s1 : Str })) ({ s1 : Str } -[[g(4)]]-> ({} -[[13(13) Str]]-> Str)), thunk(9) (({} -[[14(14)]]-> Str)) (Str -[[f(3)]]-> ({} -[[11(11)]]-> Str))]]-> Str"#
+            @r#"fun : {} -[[thunk(9) (({} -[[15]]-> { s1 : Str })) ({ s1 : Str } -[[g(4)]]-> ({} -[[13 Str]]-> Str)), thunk(9) (({} -[[14]]-> Str)) (Str -[[f(3)]]-> ({} -[[11]]-> Str))]]-> Str"#
             print_only_under_alias: true
         );
     }
@@ -7323,9 +7337,9 @@ mod solve_expr {
                 "#
             ),
             @r###"
-        Fo#f(7) : Fo, b -[[f(7)]]-> ({} -[[13(13) b]]-> ({} -[[] + b:g(4):2]-> {})) | b has G
+        Fo#f(7) : Fo, b -[[f(7)]]-> ({} -[[13 b]]-> ({} -[[] + b:g(4):2]-> {})) | b has G
-        Go#g(8) : Go -[[g(8)]]-> ({} -[[14(14)]]-> {})
+        Go#g(8) : Go -[[g(8)]]-> ({} -[[14]]-> {})
-        Fo#f(7) : Fo, Go -[[f(7)]]-> ({} -[[13(13) Go]]-> ({} -[[14(14)]]-> {}))
+        Fo#f(7) : Fo, Go -[[f(7)]]-> ({} -[[13 Go]]-> ({} -[[14]]-> {}))
         "###
         );
     }
@@ -7692,7 +7706,7 @@ mod solve_expr {
             @r###"
         const : Str -[[const(2)]]-> (Str -[[closCompose(7) (Str -a-> Str) (Str -[[]]-> Str), closConst(10) Str] as a]-> Str)
         compose : (Str -a-> Str), (Str -[[]]-> Str) -[[compose(1)]]-> (Str -a-> Str)
-        \c1, c2 -> compose c1 c2 : (Str -a-> Str), (Str -[[]]-> Str) -[[11(11)]]-> (Str -a-> Str)
+        \c1, c2 -> compose c1 c2 : (Str -a-> Str), (Str -[[]]-> Str) -[[11]]-> (Str -a-> Str)
         res : Str -[[closCompose(7) (Str -a-> Str) (Str -[[]]-> Str), closConst(10) Str] as a]-> Str
         res : Str -[[closCompose(7) (Str -a-> Str) (Str -[[]]-> Str), closConst(10) Str] as a]-> Str
         "###
@@ -8077,7 +8091,7 @@ mod solve_expr {
                 #                           ^^^^^^^^^^^^^^
                 "#
             ),
-            @"N#Decode.decoder(3) : List U8, fmt -[[7(7)]]-> { rest : List U8, result : [Err [TooShort], Ok U8] } | fmt has DecoderFormatting"
+            @"N#Decode.decoder(3) : List U8, fmt -[[7]]-> { rest : List U8, result : [Err [TooShort], Ok U8] } | fmt has DecoderFormatting"
             print_only_under_alias: true
         );
     }
@@ -8360,7 +8374,7 @@ mod solve_expr {
             ),
         @r###"
         isEqQ : ({} -[[]]-> Str), ({} -[[]]-> Str) -[[isEqQ(2)]]-> [False, True]
-        isEqQ : ({} -[[6(6), 7(7)]]-> Str), ({} -[[6(6), 7(7)]]-> Str) -[[isEqQ(2)]]-> [False, True]
+        isEqQ : ({} -[[6, 7]]-> Str), ({} -[[6, 7]]-> Str) -[[isEqQ(2)]]-> [False, True]
         "###
         print_only_under_alias: true
         );
@@ -8456,4 +8470,82 @@ mod solve_expr {
         "###
         );
     }
+
+    #[test]
+    fn disjoint_nested_lambdas_result_in_disjoint_parents_issue_4712() {
+        infer_queries!(
+            indoc!(
+                r#"
+                app "test" provides [main] to "./platform"
+
+                Parser a : {} -> a
+
+                v1 : {}
+                v1 = {}
+
+                v2 : Str
+                v2 = ""
+
+                apply : Parser (a -> Str), a -> Parser Str
+                apply = \fnParser, valParser ->
+                    \{} ->
+                        (fnParser {}) (valParser)
+
+                map : a, (a -> Str) -> Parser Str
+                map = \simpleParser, transform ->
+                    apply (\{} -> transform) simpleParser
+
+                parseInput = \{} ->
+                    when [ map v1 (\{} -> ""), map v2 (\s -> s) ] is
+                    #    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+                        _ -> ""
+
+                main = parseInput {} == ""
+                "#
+            ),
+        @r###"
+        v1 = {}
+
+        v2 = ""
+
+        apply = \fnParser, valParser-> \{} -[9]-> (fnParser {}) valParser
+
+        map = \simpleParser, transform-> apply \{} -[12]-> transform simpleParser
+
+        parseInput =
+          \{}->
+          when [
+              map v1 \{} -[13]-> "",
+              map v2 \s -[14]-> s,
+            ] is
+            _ -> ""
+
+        main = Bool.isEq (parseInput {}) ""
+
+
+        [ map v1 (\{} -> ""), map v2 (\s -> s) ] : List (({} -[[9 (({} -[[12 (Str -[[14]]-> Str)]]-> (Str -[[14]]-> Str))) Str, 9 (({} -[[12 ({} -[[13]]-> Str)]]-> ({} -[[13]]-> Str))) {}]]-> Str))
+        "###
+        print_only_under_alias: true
+        print_can_decls: true
+        );
+    }
+
+    #[test]
+    fn constrain_dbg_flex_var() {
+        infer_queries!(
+            indoc!(
+                r#"
+                app "test" provides [main] to "./platform"
+
+                polyDbg = \x ->
+                #^^^^^^^{-1}
+                    dbg x
+                    x
+
+                main = polyDbg ""
+                "#
+            ),
+        @"polyDbg : a -[[polyDbg(1)]]-> a"
+        );
+    }
 }

crates/compiler/test_derive/src/decoding.rs

@@ -103,9 +103,9 @@ fn list() {
         # Specialization lambda sets:
         #   @<1>: [[custom(3)]]
         #Derived.decoder_list =
-          Decode.custom
+          custom
             \#Derived.bytes, #Derived.fmt ->
-              Decode.decodeWith #Derived.bytes (Decode.list Decode.decoder) #Derived.fmt
+              decodeWith #Derived.bytes (list decoder) #Derived.fmt
         "###
         )
     })
@@ -121,21 +121,18 @@ fn record_2_fields() {
         # Specialization lambda sets:
         #   @<1>: [[custom(22)]]
         #Derived.decoder_{first,second} =
-          Decode.custom
+          custom
             \#Derived.bytes3, #Derived.fmt3 ->
-              Decode.decodeWith
+              decodeWith
                 #Derived.bytes3
-                (Decode.record
+                (record
                   { second: Err NoField, first: Err NoField }
                   \#Derived.stateRecord2, #Derived.field ->
                     when #Derived.field is
                       "first" ->
-                        Keep (Decode.custom
+                        Keep (custom
                           \#Derived.bytes, #Derived.fmt ->
-                            when Decode.decodeWith
+                            when decodeWith #Derived.bytes decoder #Derived.fmt is
-                                #Derived.bytes
-                                Decode.decoder
-                                #Derived.fmt is
                               #Derived.rec ->
                                 {
                                   result: when #Derived.rec.result is
@@ -145,12 +142,9 @@ fn record_2_fields() {
                                   rest: #Derived.rec.rest
                                 })
                       "second" ->
-                        Keep (Decode.custom
+                        Keep (custom
                           \#Derived.bytes2, #Derived.fmt2 ->
-                            when Decode.decodeWith
+                            when decodeWith #Derived.bytes2 decoder #Derived.fmt2 is
-                                #Derived.bytes2
-                                Decode.decoder
-                                #Derived.fmt2 is
                               #Derived.rec2 ->
                                 {
                                   result: when #Derived.rec2.result is

crates/compiler/test_derive/src/encoding.rs

@@ -187,9 +187,9 @@ fn empty_record() {
         #   @<2>: [[custom(2) {}]]
         #Derived.toEncoder_{} =
           \#Derived.rcd ->
-            Encode.custom
+            custom
               \#Derived.bytes, #Derived.fmt ->
-                Encode.appendWith #Derived.bytes (Encode.record []) #Derived.fmt
+                appendWith #Derived.bytes (record []) #Derived.fmt
         "###
         )
     })
@@ -207,9 +207,9 @@ fn zero_field_record() {
         #   @<2>: [[custom(2) {}]]
         #Derived.toEncoder_{} =
           \#Derived.rcd ->
-            Encode.custom
+            custom
               \#Derived.bytes, #Derived.fmt ->
-                Encode.appendWith #Derived.bytes (Encode.record []) #Derived.fmt
+                appendWith #Derived.bytes (record []) #Derived.fmt
         "###
         )
     })
@@ -227,11 +227,11 @@ fn one_field_record() {
         #   @<2>: [[custom(2) { a : val }]] | val has Encoding
         #Derived.toEncoder_{a} =
           \#Derived.rcd ->
-            Encode.custom
+            custom
               \#Derived.bytes, #Derived.fmt ->
-                Encode.appendWith
+                appendWith
                   #Derived.bytes
-                  (Encode.record [{ value: Encode.toEncoder #Derived.rcd.a, key: "a" }])
+                  (record [{ value: toEncoder #Derived.rcd.a, key: "a" }])
                   #Derived.fmt
         "###
         )
@@ -250,14 +250,14 @@ fn two_field_record() {
         #   @<2>: [[custom(2) { a : val, b : val1 }]] | val has Encoding, val1 has Encoding
         #Derived.toEncoder_{a,b} =
           \#Derived.rcd ->
-            Encode.custom
+            custom
               \#Derived.bytes, #Derived.fmt ->
-                Encode.appendWith
+                appendWith
                   #Derived.bytes
-                  (Encode.record
+                  (record
                     [
-                      { value: Encode.toEncoder #Derived.rcd.a, key: "a" },
+                      { value: toEncoder #Derived.rcd.a, key: "a" },
-                      { value: Encode.toEncoder #Derived.rcd.b, key: "b" },
+                      { value: toEncoder #Derived.rcd.b, key: "b" },
                     ])
                   #Derived.fmt
         "###
@@ -290,12 +290,12 @@ fn tag_one_label_zero_args() {
         #   @<2>: [[custom(2) [A]]]
         #Derived.toEncoder_[A 0] =
           \#Derived.tag ->
-            Encode.custom
+            custom
               \#Derived.bytes, #Derived.fmt ->
-                Encode.appendWith
+                appendWith
                   #Derived.bytes
                   (when #Derived.tag is
-                    A -> Encode.tag "A" [])
+                    A -> tag "A" [])
                   #Derived.fmt
         "###
         )
@@ -314,18 +314,13 @@ fn tag_one_label_two_args() {
         #   @<2>: [[custom(4) [A val val1]]] | val has Encoding, val1 has Encoding
         #Derived.toEncoder_[A 2] =
           \#Derived.tag ->
-            Encode.custom
+            custom
               \#Derived.bytes, #Derived.fmt ->
-                Encode.appendWith
+                appendWith
                   #Derived.bytes
                   (when #Derived.tag is
                     A #Derived.2 #Derived.3 ->
-                      Encode.tag
+                      tag "A" [toEncoder #Derived.2, toEncoder #Derived.3])
-                        "A"
-                        [
-                          Encode.toEncoder #Derived.2,
-                          Encode.toEncoder #Derived.3,
-                        ])
                   #Derived.fmt
         "###
         )
@@ -347,20 +342,20 @@ fn tag_two_labels() {
             #   @<2>: [[custom(6) [A val val1 val1, B val1]]] | val has Encoding, val1 has Encoding
             #Derived.toEncoder_[A 3,B 1] =
               \#Derived.tag ->
-            Encode.custom
+                custom
                   \#Derived.bytes, #Derived.fmt ->
-                Encode.appendWith
+                    appendWith
                       #Derived.bytes
                       (when #Derived.tag is
                         A #Derived.2 #Derived.3 #Derived.4 ->
-                      Encode.tag
+                          tag
                             "A"
                             [
-                          Encode.toEncoder #Derived.2,
+                              toEncoder #Derived.2,
-                          Encode.toEncoder #Derived.3,
+                              toEncoder #Derived.3,
-                          Encode.toEncoder #Derived.4,
+                              toEncoder #Derived.4,
                             ]
-                    B #Derived.5 -> Encode.tag "B" [Encode.toEncoder #Derived.5])
+                        B #Derived.5 -> tag "B" [toEncoder #Derived.5])
                       #Derived.fmt
             "###
             )
@@ -383,19 +378,14 @@ fn recursive_tag_union() {
             #   @<2>: [[custom(4) [Cons val val1, Nil]]] | val has Encoding, val1 has Encoding
             #Derived.toEncoder_[Cons 2,Nil 0] =
               \#Derived.tag ->
-            Encode.custom
+                custom
                   \#Derived.bytes, #Derived.fmt ->
-                Encode.appendWith
+                    appendWith
                       #Derived.bytes
                       (when #Derived.tag is
                         Cons #Derived.2 #Derived.3 ->
-                      Encode.tag
+                          tag "Cons" [toEncoder #Derived.2, toEncoder #Derived.3]
-                        "Cons"
+                        Nil -> tag "Nil" [])
-                        [
-                          Encode.toEncoder #Derived.2,
-                          Encode.toEncoder #Derived.3,
-                        ]
-                    Nil -> Encode.tag "Nil" [])
                       #Derived.fmt
             "###
             )
@@ -415,13 +405,11 @@ fn list() {
         #   @<2>: [[custom(4) (List val)]] | val has Encoding
         #Derived.toEncoder_list =
           \#Derived.lst ->
-            Encode.custom
+            custom
               \#Derived.bytes, #Derived.fmt ->
-                Encode.appendWith
+                appendWith
                   #Derived.bytes
-                  (Encode.list
+                  (list #Derived.lst \#Derived.elem -> toEncoder #Derived.elem)
-                    #Derived.lst
-                    \#Derived.elem -> Encode.toEncoder #Derived.elem)
                   #Derived.fmt
         "###
         )

crates/compiler/test_derive/src/hash.rs

@@ -178,7 +178,7 @@ fn one_field_record() {
         # Specialization lambda sets:
         #   @<1>: [[hash_{a}(0)]]
         #Derived.hash_{a} =
-          \#Derived.hasher, #Derived.rcd -> Hash.hash #Derived.hasher #Derived.rcd.a
+          \#Derived.hasher, #Derived.rcd -> hash #Derived.hasher #Derived.rcd.a
         "###
         )
     })
@@ -195,7 +195,7 @@ fn two_field_record() {
         #   @<1>: [[hash_{a,b}(0)]]
         #Derived.hash_{a,b} =
           \#Derived.hasher, #Derived.rcd ->
-            Hash.hash (Hash.hash #Derived.hasher #Derived.rcd.a) #Derived.rcd.b
+            hash (hash #Derived.hasher #Derived.rcd.a) #Derived.rcd.b
         "###
         )
     })
@@ -227,7 +227,7 @@ fn tag_one_label_newtype() {
         #   @<1>: [[hash_[A 2](0)]]
         #Derived.hash_[A 2] =
           \#Derived.hasher, A #Derived.2 #Derived.3 ->
-            Hash.hash (Hash.hash #Derived.hasher #Derived.2) #Derived.3
+            hash (hash #Derived.hasher #Derived.2) #Derived.3
         "###
         )
     })
@@ -246,12 +246,10 @@ fn tag_two_labels() {
           \#Derived.hasher, #Derived.union ->
             when #Derived.union is
               A #Derived.3 #Derived.4 #Derived.5 ->
-                Hash.hash
+                hash
-                  (Hash.hash
+                  (hash (hash (addU8 #Derived.hasher 0) #Derived.3) #Derived.4)
-                    (Hash.hash (Hash.addU8 #Derived.hasher 0) #Derived.3)
-                    #Derived.4)
                   #Derived.5
-              B #Derived.6 -> Hash.hash (Hash.addU8 #Derived.hasher 1) #Derived.6
+              B #Derived.6 -> hash (addU8 #Derived.hasher 1) #Derived.6
         "###
         )
     })
@@ -269,8 +267,8 @@ fn tag_two_labels_no_payloads() {
         #Derived.hash_[A 0,B 0] =
           \#Derived.hasher, #Derived.union ->
             when #Derived.union is
-              A -> Hash.addU8 #Derived.hasher 0
+              A -> addU8 #Derived.hasher 0
-              B -> Hash.addU8 #Derived.hasher 1
+              B -> addU8 #Derived.hasher 1
         "###
         )
     })
@@ -289,10 +287,8 @@ fn recursive_tag_union() {
           \#Derived.hasher, #Derived.union ->
             when #Derived.union is
               Cons #Derived.3 #Derived.4 ->
-                Hash.hash
+                hash (hash (addU8 #Derived.hasher 0) #Derived.3) #Derived.4
-                  (Hash.hash (Hash.addU8 #Derived.hasher 0) #Derived.3)
+              Nil -> addU8 #Derived.hasher 1
-                  #Derived.4
-              Nil -> Hash.addU8 #Derived.hasher 1
         "###
         )
     })

crates/compiler/test_derive/src/tests.rs

@@ -5,5 +5,4 @@ mod encoding;
 mod eq;
 mod hash;
 
-mod pretty_print;
 mod util;

crates/compiler/test_derive/src/util.rs

@@ -5,10 +5,10 @@ use bumpalo::Bump;
 use roc_packaging::cache::RocCacheDir;
 use ven_pretty::DocAllocator;
 
-use crate::pretty_print::{pretty_print_def, Ctx};
 use roc_can::{
     abilities::{AbilitiesStore, SpecializationLambdaSets},
     constraint::Constraints,
+    debug::{pretty_print_def, PPCtx},
     def::Def,
     expr::Declarations,
     module::{
@@ -529,8 +529,12 @@ where
     interns.all_ident_ids.insert(DERIVED_MODULE, ident_ids);
     DERIVED_MODULE.register_debug_idents(interns.all_ident_ids.get(&DERIVED_MODULE).unwrap());
 
-    let ctx = Ctx { interns: &interns };
+    let pp_ctx = PPCtx {
-    let derived_program = pretty_print_def(&ctx, &derived_def);
+        interns: &interns,
+        print_lambda_names: false,
+        home: builtin_module,
+    };
+    let derived_program = pretty_print_def(&pp_ctx, &derived_def);
 
     check_derived_typechecks_and_golden(
         derived_def,

crates/compiler/test_gen/src/gen_primitives.rs

@@ -4107,3 +4107,41 @@ fn issue_4349() {
         RocStr
     );
 }
+
+#[test]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+fn issue_4712() {
+    assert_evals_to!(
+        indoc!(
+            r#"
+            app "test" provides [main] to "./platform"
+
+            Parser a : {} -> a
+
+            v1 : {}
+            v1 = {}
+
+            v2 : Str
+            v2 = "cd"
+
+            apply : Parser (a -> Str), a -> Parser Str
+            apply = \fnParser, valParser ->
+                \{} ->
+                    (fnParser {}) (valParser)
+
+            map : a, (a -> Str) -> Parser Str
+            map = \simpleParser, transform ->
+                apply (\{} -> transform) simpleParser
+
+            gen = \{} ->
+                [ map v1 (\{} -> "ab"), map v2 (\s -> s) ]
+                |> List.map (\f -> f {})
+                |> Str.joinWith  ","
+
+            main = gen {}
+            "#
+        ),
+        RocStr::from("ab,cd"),
+        RocStr
+    );
+}

crates/compiler/test_gen/src/gen_tags.rs

@@ -2083,3 +2083,53 @@ fn unify_types_with_fixed_fixpoints_outside_fixing_region() {
         RocStr
     );
 }
+
+#[test]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+fn lambda_set_with_imported_toplevels_issue_4733() {
+    assert_evals_to!(
+        indoc!(
+            r#"
+            app "test" provides [main] to "./platform"
+
+            fn = \s ->
+                instr = if s == "*" then (Op Num.mul) else (Op Num.add)
+
+                Op op = instr
+
+                \a -> op a a
+
+            main = ((fn "*") 3) * ((fn "+") 5)
+            "#
+        ),
+        90,
+        i64
+    );
+}
+
+#[test]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+fn non_unary_union_with_lambda_set_with_imported_toplevels_issue_4733() {
+    assert_evals_to!(
+        indoc!(
+            r#"
+            app "test" provides [main] to "./platform"
+
+            fn = \s ->
+                instr =
+                    if s == "*" then (Op Num.mul)
+                    else if s == "+" then (Op Num.add)
+                    else Noop
+
+                when instr is
+                    Op op -> (\a -> op a a)
+                    _ -> (\a -> a)
+
+
+            main = ((fn "*") 3) * ((fn "+") 5)
+            "#
+        ),
+        90,
+        i64
+    );
+}

crates/compiler/test_mono/generated/issue_4749.txt

@@ -0,0 +1,316 @@
+procedure Bool.11 (#Attr.2, #Attr.3):
+    let Bool.23 : Int1 = lowlevel Eq #Attr.2 #Attr.3;
+    dec #Attr.3;
+    dec #Attr.2;
+    ret Bool.23;
+
+procedure Bool.11 (#Attr.2, #Attr.3):
+    let Bool.31 : Int1 = lowlevel Eq #Attr.2 #Attr.3;
+    ret Bool.31;
+
+procedure Bool.11 (#Attr.2, #Attr.3):
+    let Bool.38 : Int1 = lowlevel Eq #Attr.2 #Attr.3;
+    ret Bool.38;
+
+procedure Bool.12 (#Attr.2, #Attr.3):
+    let Bool.30 : Int1 = lowlevel NotEq #Attr.2 #Attr.3;
+    ret Bool.30;
+
+procedure Bool.7 (Bool.19, Bool.20):
+    let Bool.29 : Int1 = CallByName Bool.12 Bool.19 Bool.20;
+    ret Bool.29;
+
+procedure Decode.23 (Decode.94):
+    ret Decode.94;
+
+procedure Decode.24 (Decode.95, Decode.114, Decode.97):
+    let Decode.127 : {List U8, [C {}, C Str]} = CallByName Json.293 Decode.95 Decode.97;
+    ret Decode.127;
+
+procedure Decode.25 (Decode.98, Decode.99):
+    let Decode.126 : {} = CallByName Json.41;
+    let Decode.125 : {List U8, [C {}, C Str]} = CallByName Decode.24 Decode.98 Decode.126 Decode.99;
+    ret Decode.125;
+
+procedure Decode.26 (Decode.100, Decode.101):
+    let Decode.115 : {List U8, [C {}, C Str]} = CallByName Decode.25 Decode.100 Decode.101;
+    let Decode.103 : List U8 = StructAtIndex 0 Decode.115;
+    inc Decode.103;
+    let Decode.102 : [C {}, C Str] = StructAtIndex 1 Decode.115;
+    inc Decode.102;
+    dec Decode.115;
+    let Decode.118 : Int1 = CallByName List.1 Decode.103;
+    if Decode.118 then
+        dec Decode.103;
+        let Decode.122 : U8 = 1i64;
+        let Decode.123 : U8 = GetTagId Decode.102;
+        let Decode.124 : Int1 = lowlevel Eq Decode.122 Decode.123;
+        if Decode.124 then
+            let Decode.104 : Str = UnionAtIndex (Id 1) (Index 0) Decode.102;
+            inc Decode.104;
+            dec Decode.102;
+            let Decode.119 : [C [C List U8, C ], C Str] = TagId(1) Decode.104;
+            ret Decode.119;
+        else
+            dec Decode.102;
+            let Decode.121 : [C List U8, C ] = TagId(1) ;
+            let Decode.120 : [C [C List U8, C ], C Str] = TagId(0) Decode.121;
+            ret Decode.120;
+    else
+        dec Decode.102;
+        let Decode.117 : [C List U8, C ] = TagId(0) Decode.103;
+        let Decode.116 : [C [C List U8, C ], C Str] = TagId(0) Decode.117;
+        ret Decode.116;
+
+procedure Json.139 (Json.450, Json.451):
+    joinpoint Json.421 Json.418 Json.138:
+        let Json.141 : List U8 = StructAtIndex 0 Json.418;
+        inc Json.141;
+        let Json.140 : List U8 = StructAtIndex 1 Json.418;
+        inc Json.140;
+        dec Json.418;
+        let Json.422 : [C {}, C U8] = CallByName List.9 Json.141;
+        let Json.436 : U8 = 1i64;
+        let Json.437 : U8 = GetTagId Json.422;
+        let Json.438 : Int1 = lowlevel Eq Json.436 Json.437;
+        if Json.438 then
+            let Json.142 : U8 = UnionAtIndex (Id 1) (Index 0) Json.422;
+            let Json.424 : Int1 = CallByName Json.283 Json.142;
+            if Json.424 then
+                let Json.434 : U64 = 1i64;
+                let Json.430 : {List U8, List U8} = CallByName List.52 Json.141 Json.434;
+                let Json.431 : {} = Struct {};
+                let Json.428 : List U8 = CallByName Json.143 Json.430;
+                let Json.429 : List U8 = CallByName List.4 Json.140 Json.142;
+                let Json.426 : {List U8, List U8} = Struct {Json.428, Json.429};
+                jump Json.421 Json.426 Json.138;
+            else
+                let Json.423 : {List U8, List U8} = Struct {Json.141, Json.140};
+                ret Json.423;
+        else
+            let Json.435 : {List U8, List U8} = Struct {Json.141, Json.140};
+            ret Json.435;
+    in
+    jump Json.421 Json.450 Json.451;
+
+procedure Json.143 (Json.432):
+    let Json.433 : List U8 = StructAtIndex 1 Json.432;
+    inc Json.433;
+    dec Json.432;
+    ret Json.433;
+
+procedure Json.2 ():
+    let Json.396 : {} = Struct {};
+    ret Json.396;
+
+procedure Json.22 (Json.137, Json.138):
+    let Json.440 : List U8 = Array [];
+    let Json.420 : {List U8, List U8} = Struct {Json.137, Json.440};
+    let Json.419 : {List U8, List U8} = CallByName Json.139 Json.420 Json.138;
+    ret Json.419;
+
+procedure Json.283 (Json.284):
+    let Json.442 : U8 = 34i64;
+    let Json.441 : Int1 = CallByName Bool.7 Json.284 Json.442;
+    ret Json.441;
+
+procedure Json.293 (Json.294, Json.399):
+    let Json.400 : {List U8, [C {}, C Str]} = CallByName Json.40 Json.294;
+    ret Json.400;
+
+procedure Json.40 (Json.276):
+    let Json.446 : U64 = 1i64;
+    inc Json.276;
+    let Json.445 : {List U8, List U8} = CallByName List.52 Json.276 Json.446;
+    let Json.277 : List U8 = StructAtIndex 0 Json.445;
+    inc Json.277;
+    let Json.279 : List U8 = StructAtIndex 1 Json.445;
+    inc Json.279;
+    dec Json.445;
+    let Json.444 : U8 = 34i64;
+    let Json.443 : List U8 = Array [Json.444];
+    let Json.404 : Int1 = CallByName Bool.11 Json.277 Json.443;
+    dec Json.443;
+    dec Json.277;
+    if Json.404 then
+        dec Json.276;
+        let Json.417 : {} = Struct {};
+        let Json.416 : {List U8, List U8} = CallByName Json.22 Json.279 Json.417;
+        let Json.282 : List U8 = StructAtIndex 0 Json.416;
+        inc Json.282;
+        let Json.281 : List U8 = StructAtIndex 1 Json.416;
+        inc Json.281;
+        dec Json.416;
+        let Json.405 : [C {U64, U8}, C Str] = CallByName Str.9 Json.281;
+        let Json.413 : U8 = 1i64;
+        let Json.414 : U8 = GetTagId Json.405;
+        let Json.415 : Int1 = lowlevel Eq Json.413 Json.414;
+        if Json.415 then
+            let Json.285 : Str = UnionAtIndex (Id 1) (Index 0) Json.405;
+            inc Json.285;
+            dec Json.405;
+            let Json.409 : U64 = 1i64;
+            let Json.408 : {List U8, List U8} = CallByName List.52 Json.282 Json.409;
+            let Json.287 : List U8 = StructAtIndex 1 Json.408;
+            inc Json.287;
+            dec Json.408;
+            let Json.407 : [C {}, C Str] = TagId(1) Json.285;
+            let Json.406 : {List U8, [C {}, C Str]} = Struct {Json.287, Json.407};
+            ret Json.406;
+        else
+            dec Json.405;
+            let Json.412 : {} = Struct {};
+            let Json.411 : [C {}, C Str] = TagId(0) Json.412;
+            let Json.410 : {List U8, [C {}, C Str]} = Struct {Json.282, Json.411};
+            ret Json.410;
+    else
+        dec Json.279;
+        let Json.403 : {} = Struct {};
+        let Json.402 : [C {}, C Str] = TagId(0) Json.403;
+        let Json.401 : {List U8, [C {}, C Str]} = Struct {Json.276, Json.402};
+        ret Json.401;
+
+procedure Json.41 ():
+    let Json.398 : {} = Struct {};
+    let Json.397 : {} = CallByName Decode.23 Json.398;
+    ret Json.397;
+
+procedure List.1 (List.94):
+    let List.479 : U64 = CallByName List.6 List.94;
+    let List.480 : U64 = 0i64;
+    let List.478 : Int1 = CallByName Bool.11 List.479 List.480;
+    ret List.478;
+
+procedure List.2 (List.95, List.96):
+    let List.536 : U64 = CallByName List.6 List.95;
+    let List.532 : Int1 = CallByName Num.22 List.96 List.536;
+    if List.532 then
+        let List.534 : U8 = CallByName List.66 List.95 List.96;
+        let List.533 : [C {}, C U8] = TagId(1) List.534;
+        ret List.533;
+    else
+        let List.531 : {} = Struct {};
+        let List.530 : [C {}, C U8] = TagId(0) List.531;
+        ret List.530;
+
+procedure List.4 (List.106, List.107):
+    let List.520 : U64 = 1i64;
+    let List.518 : List U8 = CallByName List.70 List.106 List.520;
+    let List.517 : List U8 = CallByName List.71 List.518 List.107;
+    ret List.517;
+
+procedure List.49 (List.366, List.367):
+    let List.492 : U64 = StructAtIndex 0 List.367;
+    let List.493 : U64 = 0i64;
+    let List.490 : Int1 = CallByName Bool.11 List.492 List.493;
+    if List.490 then
+        dec List.366;
+        let List.491 : List U8 = Array [];
+        ret List.491;
+    else
+        let List.487 : U64 = StructAtIndex 1 List.367;
+        let List.488 : U64 = StructAtIndex 0 List.367;
+        let List.486 : List U8 = CallByName List.72 List.366 List.487 List.488;
+        ret List.486;
+
+procedure List.52 (List.381, List.382):
+    let List.383 : U64 = CallByName List.6 List.381;
+    joinpoint List.515 List.384:
+        let List.513 : U64 = 0i64;
+        let List.512 : {U64, U64} = Struct {List.384, List.513};
+        inc List.381;
+        let List.385 : List U8 = CallByName List.49 List.381 List.512;
+        let List.511 : U64 = CallByName Num.20 List.383 List.384;
+        let List.510 : {U64, U64} = Struct {List.511, List.384};
+        let List.386 : List U8 = CallByName List.49 List.381 List.510;
+        let List.509 : {List U8, List U8} = Struct {List.385, List.386};
+        ret List.509;
+    in
+    let List.516 : Int1 = CallByName Num.24 List.383 List.382;
+    if List.516 then
+        jump List.515 List.382;
+    else
+        jump List.515 List.383;
+
+procedure List.6 (#Attr.2):
+    let List.556 : U64 = lowlevel ListLen #Attr.2;
+    ret List.556;
+
+procedure List.66 (#Attr.2, #Attr.3):
+    let List.535 : U8 = lowlevel ListGetUnsafe #Attr.2 #Attr.3;
+    ret List.535;
+
+procedure List.70 (#Attr.2, #Attr.3):
+    let List.521 : List U8 = lowlevel ListReserve #Attr.2 #Attr.3;
+    ret List.521;
+
+procedure List.71 (#Attr.2, #Attr.3):
+    let List.519 : List U8 = lowlevel ListAppendUnsafe #Attr.2 #Attr.3;
+    ret List.519;
+
+procedure List.72 (#Attr.2, #Attr.3, #Attr.4):
+    let List.489 : List U8 = lowlevel ListSublist #Attr.2 #Attr.3 #Attr.4;
+    ret List.489;
+
+procedure List.9 (List.283):
+    let List.529 : U64 = 0i64;
+    let List.522 : [C {}, C U8] = CallByName List.2 List.283 List.529;
+    let List.526 : U8 = 1i64;
+    let List.527 : U8 = GetTagId List.522;
+    let List.528 : Int1 = lowlevel Eq List.526 List.527;
+    if List.528 then
+        let List.284 : U8 = UnionAtIndex (Id 1) (Index 0) List.522;
+        let List.523 : [C {}, C U8] = TagId(1) List.284;
+        ret List.523;
+    else
+        let List.525 : {} = Struct {};
+        let List.524 : [C {}, C U8] = TagId(0) List.525;
+        ret List.524;
+
+procedure Num.20 (#Attr.2, #Attr.3):
+    let Num.258 : U64 = lowlevel NumSub #Attr.2 #Attr.3;
+    ret Num.258;
+
+procedure Num.22 (#Attr.2, #Attr.3):
+    let Num.262 : Int1 = lowlevel NumLt #Attr.2 #Attr.3;
+    ret Num.262;
+
+procedure Num.24 (#Attr.2, #Attr.3):
+    let Num.261 : Int1 = lowlevel NumGt #Attr.2 #Attr.3;
+    ret Num.261;
+
+procedure Str.48 (#Attr.2, #Attr.3, #Attr.4):
+    let Str.274 : {U64, Str, Int1, U8} = lowlevel StrFromUtf8Range #Attr.2 #Attr.3 #Attr.4;
+    ret Str.274;
+
+procedure Str.9 (Str.76):
+    let Str.272 : U64 = 0i64;
+    let Str.273 : U64 = CallByName List.6 Str.76;
+    let Str.77 : {U64, Str, Int1, U8} = CallByName Str.48 Str.76 Str.272 Str.273;
+    let Str.269 : Int1 = StructAtIndex 2 Str.77;
+    if Str.269 then
+        let Str.271 : Str = StructAtIndex 1 Str.77;
+        inc Str.271;
+        dec Str.77;
+        let Str.270 : [C {U64, U8}, C Str] = TagId(1) Str.271;
+        ret Str.270;
+    else
+        let Str.267 : U8 = StructAtIndex 3 Str.77;
+        let Str.268 : U64 = StructAtIndex 0 Str.77;
+        dec Str.77;
+        let Str.266 : {U64, U8} = Struct {Str.268, Str.267};
+        let Str.265 : [C {U64, U8}, C Str] = TagId(0) Str.266;
+        ret Str.265;
+
+procedure Test.3 ():
+    let Test.0 : List U8 = Array [82i64, 111i64, 99i64];
+    let Test.8 : {} = CallByName Json.2;
+    inc Test.0;
+    let Test.1 : [C [C List U8, C ], C Str] = CallByName Decode.26 Test.0 Test.8;
+    let Test.7 : Str = "Roc";
+    let Test.6 : [C [C List U8, C ], C Str] = TagId(1) Test.7;
+    inc Test.1;
+    let Test.5 : Int1 = CallByName Bool.11 Test.1 Test.6;
+    expect Test.5;
+    let Test.4 : {} = Struct {};
+    ret Test.4;

crates/compiler/test_mono/generated/lambda_set_with_imported_toplevels_issue_4733.txt

@@ -0,0 +1,49 @@
+procedure Bool.11 (#Attr.2, #Attr.3):
+    let Bool.23 : Int1 = lowlevel Eq #Attr.2 #Attr.3;
+    ret Bool.23;
+
+procedure Bool.2 ():
+    let Bool.24 : Int1 = true;
+    ret Bool.24;
+
+procedure Num.19 (#Attr.2, #Attr.3):
+    let Num.256 : U64 = lowlevel NumAdd #Attr.2 #Attr.3;
+    ret Num.256;
+
+procedure Num.21 (#Attr.2, #Attr.3):
+    let Num.257 : U64 = lowlevel NumMul #Attr.2 #Attr.3;
+    ret Num.257;
+
+procedure Test.0 (Test.8):
+    let Test.23 : Int1 = CallByName Bool.2;
+    if Test.23 then
+        let Test.24 : Int1 = true;
+        ret Test.24;
+    else
+        let Test.22 : Int1 = false;
+        ret Test.22;
+
+procedure Test.5 (Test.6, Test.2):
+    joinpoint Test.19 Test.18:
+        ret Test.18;
+    in
+    switch Test.2:
+        case 0:
+            let Test.20 : U64 = CallByName Num.19 Test.6 Test.6;
+            jump Test.19 Test.20;
+    
+        default:
+            let Test.21 : U64 = CallByName Num.21 Test.6 Test.6;
+            jump Test.19 Test.21;
+    
+
+procedure Test.7 ():
+    let Test.13 : U64 = 3i64;
+    let Test.15 : {} = Struct {};
+    let Test.14 : Int1 = CallByName Test.0 Test.15;
+    let Test.11 : U64 = CallByName Test.5 Test.13 Test.14;
+    let Test.12 : U64 = 9i64;
+    let Test.10 : Int1 = CallByName Bool.11 Test.11 Test.12;
+    expect Test.10;
+    let Test.9 : {} = Struct {};
+    ret Test.9;

crates/compiler/test_mono/src/tests.rs

@@ -2159,3 +2159,36 @@ fn issue_4705() {
         "###
     )
 }
+
+#[mono_test(mode = "test")]
+fn issue_4749() {
+    indoc!(
+        r###"
+        interface Test exposes [] imports [Json]
+
+        expect
+            input = [82, 111, 99]
+            got = Decode.fromBytes input Json.fromUtf8 
+            got == Ok "Roc"
+        "###
+    )
+}
+
+#[mono_test(mode = "test", no_check)]
+fn lambda_set_with_imported_toplevels_issue_4733() {
+    indoc!(
+        r###"
+        interface Test exposes [] imports []
+
+        fn = \{} ->
+            instr : [ Op (U64, U64 -> U64) ]
+            instr = if Bool.true then (Op Num.mul) else (Op Num.add)
+
+            Op op = instr
+
+            \a -> op a a
+
+        expect ((fn {}) 3) == 9
+        "###
+    )
+}

crates/compiler/types/src/pretty_print.rs

@@ -767,18 +767,23 @@ fn write_content<'a>(
             buf.push_str("[[");
 
             let print_symbol = |symbol: &Symbol| {
+                let ident_str = symbol.as_str(env.interns);
+                let ident_index_str = symbol.ident_id().index().to_string();
+                let disambiguation = if ident_str != ident_index_str {
+                    // The pretty name is a named identifier; print the ident as well to avoid
+                    // ambguity (in shadows or ability specializations).
+                    format!("({ident_index_str})")
+                } else {
+                    "".to_string()
+                };
                 if env.home == symbol.module_id() {
-                    format!(
+                    format!("{}{}", ident_str, disambiguation,)
-                        "{}({})",
-                        symbol.as_str(env.interns),
-                        symbol.ident_id().index(),
-                    )
                 } else {
                     format!(
-                        "{}.{}({})",
+                        "{}.{}{}",
                         symbol.module_string(env.interns),
-                        symbol.as_str(env.interns),
+                        ident_str,
-                        symbol.ident_id().index(),
+                        disambiguation
                     )
                 }
             };

crates/compiler/types/src/types.rs

@@ -3645,11 +3645,8 @@ impl Alias {
 #[derive(PartialEq, Eq, Debug, Clone)]
 pub enum Mismatch {
     TypeMismatch,
-    IfConditionNotBool,
-    InconsistentIfElse,
-    InconsistentWhenBranches,
-    CanonicalizationProblem,
     TypeNotInRange,
+    DisjointLambdaSets,
     DoesNotImplementAbiity(Variable, Symbol),
 }
 

crates/compiler/unify/src/unify.rs

@@ -320,7 +320,6 @@ impl<M: MetaCollector> Outcome<M> {
 
 pub struct Env<'a> {
     pub subs: &'a mut Subs,
-    compute_outcome_only: bool,
     seen_recursion: VecSet<(Variable, Variable)>,
     fixed_variables: VecSet<Variable>,
 }
@@ -329,21 +328,11 @@ impl<'a> Env<'a> {
     pub fn new(subs: &'a mut Subs) -> Self {
         Self {
             subs,
-            compute_outcome_only: false,
             seen_recursion: Default::default(),
             fixed_variables: Default::default(),
         }
     }
 
-    // Computes a closure in outcome-only mode. Unifications run in outcome-only mode will check
-    // for unifiability, but will not modify type variables or merge them.
-    pub fn with_outcome_only<T>(&mut self, f: impl FnOnce(&mut Self) -> T) -> T {
-        self.compute_outcome_only = true;
-        let result = f(self);
-        self.compute_outcome_only = false;
-        result
-    }
-
     fn add_recursion_pair(&mut self, var1: Variable, var2: Variable) {
         let pair = (
             self.subs.get_root_key_without_compacting(var1),
@@ -1331,7 +1320,7 @@ fn separate_union_lambdas<M: MetaCollector>(
     mode: Mode,
     fields1: UnionLambdas,
     fields2: UnionLambdas,
-) -> (Outcome<M>, SeparatedUnionLambdas) {
+) -> Result<(Outcome<M>, SeparatedUnionLambdas), Outcome<M>> {
     debug_assert!(
         fields1.is_sorted_allow_duplicates(env.subs),
         "not sorted: {:?}",
@@ -1451,20 +1440,56 @@ fn separate_union_lambdas<M: MetaCollector>(
                             //
                             // If they are not unifiable, that means the two lambdas must be
                             // different (since they have different capture sets), and so we don't
-                            // want to merge the variables.
+                            // want to merge the variables. Instead, we'll treat the lambda sets
-                            let variables_are_unifiable = env.with_outcome_only(|env| {
+                            // are disjoint, and keep them as independent lambda in the resulting
-                                unify_pool::<NoCollector>(env, pool, var1, var2, mode)
+                            // set.
-                                    .mismatches
+                            //
-                                    .is_empty()
+                            // # Nested lambda sets
-                            });
+                            //
+                            // XREF https://github.com/roc-lang/roc/issues/4712
+                            //
+                            // We must be careful to ensure that if unifying nested lambda sets
+                            // results in disjoint lambdas, that the parent lambda sets are
+                            // ultimately treated disjointly as well.
+                            // Consider
+                            //
+                            //   v1: {} -[ foo ({} -[ bar Str ]-> {}) ]-> {}
+                            // ~ v2: {} -[ foo ({} -[ bar U64 ]-> {}) ]-> {}
+                            //
+                            // When considering unification of the nested sets
+                            //
+                            //   [ bar Str ]
+                            // ~ [ bar U64 ]
+                            //
+                            // we should not unify these sets, even disjointly, because that would
+                            // ultimately lead us to unifying
+                            //
+                            // v1 ~ v2
+                            // => {} -[ foo ({} -[ bar Str, bar U64 ]-> {}) ] -> {}
+                            //
+                            // which is quite wrong - we do not have a lambda `foo` that captures
+                            // either `bar captures: Str` or `bar captures: U64`, we have two
+                            // different lambdas `foo` that capture different `bars`. The target
+                            // unification is
+                            //
+                            // v1 ~ v2
+                            // => {} -[ foo ({} -[ bar Str ]-> {}),
+                            //          foo ({} -[ bar U64 ]-> {}) ] -> {}
+                            let subs_snapshot = env.subs.snapshot();
+                            let pool_snapshot = pool.len();
+                            let outcome: Outcome<M> = unify_pool(env, pool, var1, var2, mode);
 
-                            if !variables_are_unifiable {
+                            if !outcome.mismatches.is_empty() {
+                                // Rolling back will also pull apart any nested lambdas that
+                                // were joined into the same set.
+                                env.subs.rollback_to(subs_snapshot);
+                                pool.truncate(pool_snapshot);
                                 continue 'try_next_right;
-                            }
+                            } else {
-
                                 let outcome = unify_pool(env, pool, var1, var2, mode);
                                 whole_outcome.union(outcome);
                             }
+                        }
 
                         // All the variables unified, so we can join the left + right.
                         // The variables are unified in left and right slice, so just reuse the left slice.
@@ -1487,14 +1512,14 @@ fn separate_union_lambdas<M: MetaCollector>(
         }
     }
 
-    (
+    Ok((
         whole_outcome,
         SeparatedUnionLambdas {
             only_in_left,
             only_in_right,
             joined,
         },
-    )
+    ))
 }
 
 /// ULS-SORT-ORDER:
@@ -1829,7 +1854,10 @@ fn unify_lambda_set_help<M: MetaCollector>(
             only_in_right,
             joined,
         },
-    ) = separate_union_lambdas(env, pool, ctx.mode, solved1, solved2);
+    ) = match separate_union_lambdas(env, pool, ctx.mode, solved1, solved2) {
+        Ok((outcome, separated)) => (outcome, separated),
+        Err(err_outcome) => return err_outcome,
+    };
 
     let all_lambdas = joined
         .into_iter()
@@ -3495,7 +3523,6 @@ fn unify_recursion<M: MetaCollector>(
 pub fn merge<M: MetaCollector>(env: &mut Env, ctx: &Context, content: Content) -> Outcome<M> {
     let mut outcome: Outcome<M> = Outcome::default();
 
-    if !env.compute_outcome_only {
     let rank = ctx.first_desc.rank.min(ctx.second_desc.rank);
     let desc = Descriptor {
         content,
@@ -3512,7 +3539,6 @@ pub fn merge<M: MetaCollector>(env: &mut Env, ctx: &Context, content: Content) -
         .record_changed_variable(env.subs, ctx.second);
 
     env.subs.union(ctx.first, ctx.second, desc);
-    }
 
     outcome
 }

crates/glue/src/RocType.roc

@@ -91,7 +91,6 @@ RocNum : [
     U128,
     F32,
     F64,
-    F128,
     Dec,
 ]
 

crates/glue/src/glue.rs

@@ -571,7 +571,6 @@ struct RocType_RocDict {
 #[repr(u8)]
 pub enum RocNum {
     Dec = 0,
-    F128 = 1,
     F32 = 2,
     F64 = 3,
     I128 = 4,
@@ -590,7 +589,6 @@ impl core::fmt::Debug for RocNum {
     fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
         match self {
             Self::Dec => f.write_str("RocNum::Dec"),
-            Self::F128 => f.write_str("RocNum::F128"),
             Self::F32 => f.write_str("RocNum::F32"),
             Self::F64 => f.write_str("RocNum::F64"),
             Self::I128 => f.write_str("RocNum::I128"),

crates/glue/src/rust_glue.rs

@@ -1737,7 +1737,6 @@ fn type_name(id: TypeId, types: &Types) -> String {
         RocType::Num(RocNum::I128) => "roc_std::I128".to_string(),
         RocType::Num(RocNum::F32) => "f32".to_string(),
         RocType::Num(RocNum::F64) => "f64".to_string(),
-        RocType::Num(RocNum::F128) => "roc_std::F128".to_string(),
         RocType::Num(RocNum::Dec) => "roc_std::RocDec".to_string(),
         RocType::RocDict(key_id, val_id) => format!(
             "roc_std::RocDict<{}, {}>",
@@ -2433,7 +2432,7 @@ fn has_float_help(roc_type: &RocType, types: &Types, do_not_recurse: &[TypeId])
             use RocNum::*;
 
             match num {
-                F32 | F64 | F128 => true,
+                F32 | F64 => true,
                 I8 | U8 | I16 | U16 | I32 | U32 | I64 | U64 | I128 | U128 | Dec => false,
             }
         }

crates/glue/src/types.rs

@@ -544,7 +544,6 @@ pub enum RocNum {
     U128,
     F32,
     F64,
-    F128,
     Dec,
 }
 
@@ -566,7 +565,6 @@ impl RocNum {
             RocNum::U128 => size_of::<roc_std::U128>(),
             RocNum::F32 => size_of::<f32>(),
             RocNum::F64 => size_of::<f64>(),
-            RocNum::F128 => todo!(),
             RocNum::Dec => size_of::<roc_std::RocDec>(),
         };
 
@@ -1083,11 +1081,6 @@ fn add_builtin_type<'a>(
                 RocType::Num(RocNum::F64),
                 layout,
             ),
-            F128 => types.add_anonymous(
-                &env.layout_cache.interner,
-                RocType::Num(RocNum::F128),
-                layout,
-            ),
         },
         (Builtin::Decimal, _) => types.add_anonymous(
             &env.layout_cache.interner,

crates/repl_eval/src/eval.rs

@@ -172,7 +172,7 @@ fn unroll_newtypes_and_aliases<'a, 'env>(
                 var = field.into_inner();
             }
             Content::Alias(name, _, real_var, kind) => {
-                if *name == Symbol::BOOL_BOOL {
+                if *name == Symbol::BOOL_BOOL || name.module_id() == ModuleId::NUM {
                     return (newtype_containers, alias_content, var);
                 }
                 // We need to pass through aliases too, because their underlying types may have
@@ -185,7 +185,7 @@ fn unroll_newtypes_and_aliases<'a, 'env>(
                 //
                 // At the end of the day what we should show to the user is the alias content, not
                 // what's inside, so keep that around too.
-                if *kind == AliasKind::Opaque && name.module_id() != ModuleId::NUM {
+                if *kind == AliasKind::Opaque {
                     newtype_containers.push(NewtypeKind::Opaque(*name));
                 }
                 alias_content = Some(content);
@@ -361,10 +361,11 @@ fn jit_to_ast_help<'a, A: ReplApp<'a>>(
             use Content::*;
             use IntWidth::*;
 
-            match (alias_content, int_width) {
+            match (env.subs.get_content_without_compacting(raw_var), int_width) {
-                (Some(Alias(Symbol::NUM_UNSIGNED8, ..)), U8) => num_helper!(u8),
+                (Alias(Symbol::NUM_UNSIGNED8 | Symbol::NUM_U8, ..), U8) => num_helper!(u8),
                 (_, U8) => {
                     // This is not a number, it's a tag union or something else
+                    dbg!(&alias_content);
                     app.call_function(main_fn_name, |_mem: &A::Memory, num: u8| {
                         byte_to_ast(env, num, env.subs.get_content_without_compacting(raw_var))
                     })
@@ -387,7 +388,6 @@ fn jit_to_ast_help<'a, A: ReplApp<'a>>(
             match float_width {
                 F32 => num_helper!(f32),
                 F64 => num_helper!(f64),
-                F128 => todo!("F128 not implemented"),
             }
         }
         Layout::Builtin(Builtin::Decimal) => num_helper!(RocDec),
@@ -565,7 +565,13 @@ fn addr_to_ast<'a, M: ReplAppMemory>(
             use IntWidth::*;
 
             match int_width {
-                U8 => helper!(deref_u8, u8),
+                U8 => {
+                    if matches!(raw_content, Content::Alias(name, ..) if name.module_id() == ModuleId::NUM) {
+                        helper!(deref_u8, u8)
+                    } else {
+                        byte_to_ast(env, mem.deref_u8(addr), raw_content)
+                    }
+                },
                 U16 => helper!(deref_u16, u16),
                 U32 => helper!(deref_u32, u32),
                 U64 => helper!(deref_u64, u64),
@@ -583,7 +589,6 @@ fn addr_to_ast<'a, M: ReplAppMemory>(
             match float_width {
                 F32 => helper!(deref_f32, f32),
                 F64 => helper!(deref_f64, f64),
-                F128 => todo!("F128 not implemented"),
             }
         }
         (_, Layout::Builtin(Builtin::List(elem_layout))) => {

crates/repl_expect/src/lib.rs

@@ -32,9 +32,10 @@ pub fn get_values<'a>(
     layout_interner: &Arc<GlobalInterner<'a, Layout<'a>>>,
     start: *const u8,
     start_offset: usize,
-    variables: &[Variable],
+    number_of_lookups: usize,
-) -> (usize, Vec<Expr<'a>>) {
+) -> (usize, Vec<Expr<'a>>, Vec<Variable>) {
-    let mut result = Vec::with_capacity(variables.len());
+    let mut result = Vec::with_capacity(number_of_lookups);
+    let mut result_vars = Vec::with_capacity(number_of_lookups);
 
     let memory = ExpectMemory { start };
 
@@ -45,13 +46,20 @@ pub fn get_values<'a>(
 
     let app = arena.alloc(app);
 
-    for (i, variable) in variables.iter().enumerate() {
+    for i in 0..number_of_lookups {
-        let start = app.memory.deref_usize(start_offset + i * 8);
+        let size_of_lookup_header = 8 /* pointer to value */ + 4 /* type variable */;
+
+        let start = app
+            .memory
+            .deref_usize(start_offset + i * size_of_lookup_header);
+        let variable = app.memory.deref_u32(
+            start_offset + i * size_of_lookup_header + 8, /* skip the pointer */
+        );
+        let variable = unsafe { Variable::from_index(variable) };
+
         app.offset = start;
 
         let expr = {
-            let variable = *variable;
-
             // TODO: pass layout_cache to jit_to_ast directly
             let mut layout_cache = LayoutCache::new(layout_interner.fork(), target_info);
             let layout = layout_cache.from_var(arena, variable, subs).unwrap();
@@ -76,9 +84,10 @@ pub fn get_values<'a>(
         };
 
         result.push(expr);
+        result_vars.push(variable);
     }
 
-    (app.offset, result)
+    (app.offset, result, result_vars)
 }
 
 #[cfg(not(windows))]

crates/repl_expect/src/run.rs

@@ -25,7 +25,7 @@ use roc_mono::{ir::OptLevel, layout::Layout};
 use roc_region::all::Region;
 use roc_reporting::{error::expect::Renderer, report::RenderTarget};
 use roc_target::TargetInfo;
-use roc_types::subs::{Subs, Variable};
+use roc_types::subs::Subs;
 use target_lexicon::Triple;
 
 pub struct ExpectMemory<'a> {
@@ -471,7 +471,7 @@ pub fn render_dbgs_in_memory<'a>(
     )
 }
 
-fn split_expect_lookups(subs: &Subs, lookups: &[ExpectLookup]) -> (Vec<Symbol>, Vec<Variable>) {
+fn split_expect_lookups(subs: &Subs, lookups: &[ExpectLookup]) -> Vec<Symbol> {
     lookups
         .iter()
         .filter_map(
@@ -485,11 +485,11 @@ fn split_expect_lookups(subs: &Subs, lookups: &[ExpectLookup]) -> (Vec<Symbol>,
                 if subs.is_function(*var) {
                     None
                 } else {
-                    Some((*symbol, *var))
+                    Some(*symbol)
                 }
             },
         )
-        .unzip()
+        .collect()
 }
 
 #[allow(clippy::too_many_arguments)]
@@ -523,15 +523,7 @@ fn render_dbg_failure<'a>(
 
     let subs = arena.alloc(&mut data.subs);
 
-    let current = ExpectLookup {
+    let (offset, expressions, _variables) = crate::get_values(
-        symbol: current.symbol,
-        var: current.var,
-        ability_info: current.ability_info,
-    };
-
-    let (_symbols, variables) = split_expect_lookups(subs, &[current]);
-
-    let (offset, expressions) = crate::get_values(
         target_info,
         arena,
         subs,
@@ -539,7 +531,7 @@ fn render_dbg_failure<'a>(
         layout_interner,
         start,
         frame.start_offset,
-        &variables,
+        1,
     );
 
     renderer.render_dbg(writer, &expressions, expect_region, failure_region)?;
@@ -574,24 +566,23 @@ fn render_expect_failure<'a>(
         None => panic!("region {failure_region:?} not in list of expects"),
         Some(current) => current,
     };
-    let subs = arena.alloc(&mut data.subs);
 
-    let (symbols, variables) = split_expect_lookups(subs, current);
+    let symbols = split_expect_lookups(&data.subs, current);
 
-    let (offset, expressions) = crate::get_values(
+    let (offset, expressions, variables) = crate::get_values(
         target_info,
         arena,
-        subs,
+        &data.subs,
         interns,
         layout_interner,
         start,
         frame.start_offset,
-        &variables,
+        symbols.len(),
     );
 
     renderer.render_failure(
         writer,
-        subs,
+        &mut data.subs,
         &symbols,
         &variables,
         &expressions,

crates/repl_test/src/tests.rs

@@ -1256,3 +1256,15 @@ fn newtype_by_void_is_wrapped() {
         r#"Ok 43 : Result (Num *) err"#,
     );
 }
+
+#[test]
+fn enum_tag_union_in_list() {
+    expect_success(
+        indoc!(
+            r#"
+            [E, F, G, H]
+            "#
+        ),
+        r#"[E, F, G, H] : List [E, F, G, H]"#,
+    );
+}

flake.nix

@@ -105,7 +105,8 @@
           debugir
           rust
           rust-bindgen
-          cargo-criterion
+          cargo-criterion # for benchmarks
+          simple-http-server # to view roc website when trying out edits
         ]);
       in {
 

mlc_config.json

@@ -23,6 +23,9 @@
         },
         {
             "pattern": "https://web.eecs.umich.edu"
+        },
+        {
+            "pattern": "http://0.0.0.0:8000"
         }
     ]
 }

www/README.md

@@ -1,10 +1,9 @@
 # www.roc-lang.org
 
-## How to update site
+To view the website after you've made a change, execute:
-
+```bash
-- create a new branch, for example `update-www` based on `www`
+./www/build.sh
-- pull `main` into `update-www`
+cd www/build
-- update for example the file `www/public/index.html`
+simple-http-server # If you're using the nix flake simple-http-server will already be installed. Withouth nix you can install it with `cargo install simple-http-server`.
-- do a PR against `www`
+```
-- check deploy preview
+Open http://0.0.0.0:8000 in your browser.
-- review and merge

www/public/tutorial/index.html

@@ -1195,6 +1195,16 @@ expect pluralize <span class="str">"cactus"</span> <span class="str">"cacti"</sp
 </samp>
 <p>If you put this in a file named <code>main.roc</code> and run <code>roc test</code>, Roc will execute the two <code>expect</code>
 expressions (that is, the two <code>pluralize</code> calls) and report any that returned <code>false</code>.</p>
+
+<p>If a test fails, it will not show the actual value that differs from the expected value.
+To show the actual value, you can write the expect like this:</p>
+
+<samp>expect
+    funcOut <span class="op">=</span> pluralize <span class="str">"cactus"</span> <span class="str">"cacti"</span> 1
+
+    funcOut <span class="op">==</span> <span class="str">"2 cactus"</span>
+</samp>
+
 <h3 id="inline-expects"><a href="#inline-expects">Inline Expectations</a></h3>
 <p>For example:</p>
 <samp>    <span class="kw">if</span> count <span class="op">==</span> <span class="number">1</span> then