parse error infrastructure

cli/src/main.rs

@@ -156,8 +156,7 @@ fn gen(
     target: Triple,
     dest_filename: &Path,
 ) {
-    use roc_reporting::report::{can_problem, RocDocAllocator, DEFAULT_PALETTE};
-    use roc_reporting::type_error::type_problem;
+    use roc_reporting::report::{can_problem, type_problem, RocDocAllocator, DEFAULT_PALETTE};
 
     let src = loaded.src;
     let home = loaded.module_id;

compiler/reporting/src/error/canonicalize.rs

@@ -0,0 +1,397 @@
+use roc_collections::all::MutSet;
+use roc_problem::can::PrecedenceProblem::BothNonAssociative;
+use roc_problem::can::{Problem, RuntimeError};
+use std::path::PathBuf;
+
+use crate::report::{Annotation, Report, RocDocAllocator, RocDocBuilder};
+use ven_pretty::DocAllocator;
+
+pub fn can_problem<'b>(
+    alloc: &'b RocDocAllocator<'b>,
+    filename: PathBuf,
+    problem: Problem,
+) -> Report<'b> {
+    let doc = match problem {
+        Problem::UnusedDef(symbol, region) => {
+            let line =
+                r#" then remove it so future readers of your code don't wonder why it is there."#;
+
+            alloc.stack(vec![
+                alloc
+                    .symbol_unqualified(symbol)
+                    .append(alloc.reflow(" is not used anywhere in your code.")),
+                alloc.region(region),
+                alloc
+                    .reflow("If you didn't intend on using ")
+                    .append(alloc.symbol_unqualified(symbol))
+                    .append(alloc.reflow(line)),
+            ])
+        }
+        Problem::UnusedImport(module_id, region) => alloc.concat(vec![
+            alloc.reflow("Nothing from "),
+            alloc.module(module_id),
+            alloc.reflow(" is used in this module."),
+            alloc.region(region),
+            alloc.reflow("Since "),
+            alloc.module(module_id),
+            alloc.reflow(" isn't used, you don't need to import it."),
+        ]),
+        Problem::UnusedArgument(closure_symbol, argument_symbol, region) => {
+            let line = "\". Adding an underscore at the start of a variable name is a way of saying that the variable is not used.";
+
+            alloc.concat(vec![
+                alloc.symbol_unqualified(closure_symbol),
+                alloc.reflow(" doesn't use "),
+                alloc.symbol_unqualified(argument_symbol),
+                alloc.reflow("."),
+                alloc.region(region),
+                alloc.reflow("If you don't need "),
+                alloc.symbol_unqualified(argument_symbol),
+                alloc.reflow(", then you can just remove it. However, if you really do need "),
+                alloc.symbol_unqualified(argument_symbol),
+                alloc.reflow(" as an argument of "),
+                alloc.symbol_unqualified(closure_symbol),
+                alloc.reflow(", prefix it with an underscore, like this: \"_"),
+                alloc.symbol_unqualified(argument_symbol),
+                alloc.reflow(line),
+            ])
+        }
+        Problem::PrecedenceProblem(BothNonAssociative(region, left_bin_op, right_bin_op)) => alloc
+            .stack(vec![
+                if left_bin_op.value == right_bin_op.value {
+                    alloc.concat(vec![
+                        alloc.reflow("Using more than one "),
+                        alloc.binop(left_bin_op.value),
+                        alloc.reflow(concat!(
+                            " like this requires parentheses,",
+                            " to clarify how things should be grouped.",
+                        )),
+                    ])
+                } else {
+                    alloc.concat(vec![
+                        alloc.reflow("Using "),
+                        alloc.binop(left_bin_op.value),
+                        alloc.reflow(" and "),
+                        alloc.binop(right_bin_op.value),
+                        alloc.reflow(concat!(
+                            " together requires parentheses, ",
+                            "to clarify how they should be grouped."
+                        )),
+                    ])
+                },
+                alloc.region(region),
+            ]),
+        Problem::UnsupportedPattern(pattern_type, region) => {
+            use roc_parse::pattern::PatternType::*;
+
+            let this_thing = match pattern_type {
+                TopLevelDef => "a top-level definition:",
+                DefExpr => "a value definition:",
+                FunctionArg => "function arguments:",
+                WhenBranch => unreachable!("all patterns are allowed in a When"),
+            };
+
+            let suggestion = vec![
+                alloc.reflow(
+                    "Patterns like this don't cover all possible shapes of the input type. Use a ",
+                ),
+                alloc.keyword("when"),
+                alloc.reflow(" ... "),
+                alloc.keyword("is"),
+                alloc.reflow(" instead."),
+            ];
+
+            alloc.stack(vec![
+                alloc
+                    .reflow("This pattern is not allowed in ")
+                    .append(alloc.reflow(this_thing)),
+                alloc.region(region),
+                alloc.concat(suggestion),
+            ])
+        }
+        Problem::ShadowingInAnnotation {
+            original_region,
+            shadow,
+        } => pretty_runtime_error(
+            alloc,
+            RuntimeError::Shadowing {
+                original_region,
+                shadow,
+            },
+        ),
+        Problem::CyclicAlias(symbol, region, others) => {
+            let (doc, title) = crate::error::r#type::cyclic_alias(alloc, symbol, region, others);
+
+            return Report {
+                filename,
+                title,
+                doc,
+            };
+        }
+        Problem::PhantomTypeArgument {
+            alias,
+            variable_region,
+            variable_name,
+        } => alloc.stack(vec![
+            alloc.concat(vec![
+                alloc.reflow("The "),
+                alloc.type_variable(variable_name),
+                alloc.reflow(" type variable is not used in the "),
+                alloc.symbol_unqualified(alias),
+                alloc.reflow(" alias definition:"),
+            ]),
+            alloc.region(variable_region),
+            alloc.reflow("Roc does not allow unused type parameters!"),
+            // TODO add link to this guide section
+            alloc.hint().append(alloc.reflow(
+                "If you want an unused type parameter (a so-called \"phantom type\"), \
+                read the guide section on phantom data.",
+            )),
+        ]),
+        Problem::DuplicateRecordFieldValue {
+            field_name,
+            field_region,
+            record_region,
+            replaced_region,
+        } => alloc.stack(vec![
+            alloc.concat(vec![
+                alloc.reflow("This record defines the "),
+                alloc.record_field(field_name.clone()),
+                alloc.reflow(" field twice!"),
+            ]),
+            alloc.region_all_the_things(
+                record_region,
+                replaced_region,
+                field_region,
+                Annotation::Error,
+            ),
+            alloc.reflow("In the rest of the program, I will only use the latter definition:"),
+            alloc.region_all_the_things(
+                record_region,
+                field_region,
+                field_region,
+                Annotation::TypoSuggestion,
+            ),
+            alloc.concat(vec![
+                alloc.reflow("For clarity, remove the previous "),
+                alloc.record_field(field_name),
+                alloc.reflow(" definitions from this record."),
+            ]),
+        ]),
+        Problem::DuplicateRecordFieldType {
+            field_name,
+            field_region,
+            record_region,
+            replaced_region,
+        } => alloc.stack(vec![
+            alloc.concat(vec![
+                alloc.reflow("This record type defines the "),
+                alloc.record_field(field_name.clone()),
+                alloc.reflow(" field twice!"),
+            ]),
+            alloc.region_all_the_things(
+                record_region,
+                replaced_region,
+                field_region,
+                Annotation::Error,
+            ),
+            alloc.reflow("In the rest of the program, I will only use the latter definition:"),
+            alloc.region_all_the_things(
+                record_region,
+                field_region,
+                field_region,
+                Annotation::TypoSuggestion,
+            ),
+            alloc.concat(vec![
+                alloc.reflow("For clarity, remove the previous "),
+                alloc.record_field(field_name),
+                alloc.reflow(" definitions from this record type."),
+            ]),
+        ]),
+        Problem::DuplicateTag {
+            tag_name,
+            tag_union_region,
+            tag_region,
+            replaced_region,
+        } => alloc.stack(vec![
+            alloc.concat(vec![
+                alloc.reflow("This tag union type defines the "),
+                alloc.tag_name(tag_name.clone()),
+                alloc.reflow(" tag twice!"),
+            ]),
+            alloc.region_all_the_things(
+                tag_union_region,
+                replaced_region,
+                tag_region,
+                Annotation::Error,
+            ),
+            alloc.reflow("In the rest of the program, I will only use the latter definition:"),
+            alloc.region_all_the_things(
+                tag_union_region,
+                tag_region,
+                tag_region,
+                Annotation::TypoSuggestion,
+            ),
+            alloc.concat(vec![
+                alloc.reflow("For clarity, remove the previous "),
+                alloc.tag_name(tag_name),
+                alloc.reflow(" definitions from this tag union type."),
+            ]),
+        ]),
+        Problem::RuntimeError(runtime_error) => pretty_runtime_error(alloc, runtime_error),
+    };
+
+    Report {
+        title: "SYNTAX PROBLEM".to_string(),
+        filename,
+        doc,
+    }
+}
+
+fn pretty_runtime_error<'b>(
+    alloc: &'b RocDocAllocator<'b>,
+    runtime_error: RuntimeError,
+) -> RocDocBuilder<'b> {
+    match runtime_error {
+        RuntimeError::Shadowing {
+            original_region,
+            shadow,
+        } => {
+            let line = r#"Since these variables have the same name, it's easy to use the wrong one on accident. Give one of them a new name."#;
+
+            alloc.stack(vec![
+                alloc
+                    .text("The ")
+                    .append(alloc.ident(shadow.value))
+                    .append(alloc.reflow(" name is first defined here:")),
+                alloc.region(original_region),
+                alloc.reflow("But then it's defined a second time here:"),
+                alloc.region(shadow.region),
+                alloc.reflow(line),
+            ])
+        }
+
+        RuntimeError::LookupNotInScope(loc_name, options) => {
+            not_found(alloc, loc_name.region, &loc_name.value, "value", options)
+        }
+        RuntimeError::CircularDef(mut idents, regions) => {
+            let first = idents.remove(0);
+
+            if idents.is_empty() {
+                alloc
+                    .reflow("The ")
+                    .append(alloc.ident(first.value.clone()))
+                    .append(alloc.reflow(
+                        " value is defined directly in terms of itself, causing an infinite loop.",
+                    ))
+            // TODO "are you trying to mutate a variable?
+            // TODO hint?
+            } else {
+                alloc.stack(vec![
+                    alloc
+                        .reflow("The ")
+                        .append(alloc.ident(first.value.clone()))
+                        .append(
+                            alloc.reflow(" definition is causing a very tricky infinite loop:"),
+                        ),
+                    alloc.region(regions[0].0),
+                    alloc
+                        .reflow("The ")
+                        .append(alloc.ident(first.value.clone()))
+                        .append(alloc.reflow(
+                            " value depends on itself through the following chain of definitions:",
+                        )),
+                    crate::report::cycle(
+                        alloc,
+                        4,
+                        alloc.ident(first.value),
+                        idents
+                            .into_iter()
+                            .map(|ident| alloc.ident(ident.value))
+                            .collect::<Vec<_>>(),
+                    ),
+                    // TODO hint?
+                ])
+            }
+        }
+        other => {
+            //    // Example: (5 = 1 + 2) is an unsupported pattern in an assignment; Int patterns aren't allowed in assignments!
+            //    UnsupportedPattern(Region),
+            //    UnrecognizedFunctionName(Located<InlinableString>),
+            //    SymbolNotExposed {
+            //        module_name: InlinableString,
+            //        ident: InlinableString,
+            //        region: Region,
+            //    },
+            //    ModuleNotImported {
+            //        module_name: InlinableString,
+            //        ident: InlinableString,
+            //        region: Region,
+            //    },
+            //    InvalidPrecedence(PrecedenceProblem, Region),
+            //    MalformedIdentifier(Box<str>, Region),
+            //    MalformedClosure(Region),
+            //    FloatOutsideRange(Box<str>),
+            //    IntOutsideRange(Box<str>),
+            //    InvalidHex(std::num::ParseIntError, Box<str>),
+            //    InvalidOctal(std::num::ParseIntError, Box<str>),
+            //    InvalidBinary(std::num::ParseIntError, Box<str>),
+            //    QualifiedPatternIdent(InlinableString),
+            //    CircularDef(
+            //        Vec<Located<Ident>>,
+            //        Vec<(Region /* pattern */, Region /* expr */)>,
+            //    ),
+            //
+            //    /// When the author specifies a type annotation but no implementation
+            //    NoImplementation,
+            todo!("TODO implement run time error reporting for {:?}", other)
+        }
+    }
+}
+
+fn not_found<'b>(
+    alloc: &'b RocDocAllocator<'b>,
+    region: roc_region::all::Region,
+    name: &str,
+    thing: &'b str,
+    options: MutSet<Box<str>>,
+) -> RocDocBuilder<'b> {
+    use crate::error::r#type::suggest;
+
+    let mut suggestions = suggest::sort(name, options.iter().map(|v| v.as_ref()).collect());
+    suggestions.truncate(4);
+
+    let default_no = alloc.concat(vec![
+        alloc.reflow("Is there an "),
+        alloc.keyword("import"),
+        alloc.reflow(" or "),
+        alloc.keyword("exposing"),
+        alloc.reflow(" missing up-top"),
+    ]);
+
+    let default_yes = alloc.reflow("these names seem close though:");
+
+    let to_details = |no_suggestion_details, yes_suggestion_details| {
+        if suggestions.is_empty() {
+            no_suggestion_details
+        } else {
+            alloc.stack(vec![
+                yes_suggestion_details,
+                alloc
+                    .vcat(suggestions.into_iter().map(|v| alloc.string(v.to_string())))
+                    .indent(4),
+            ])
+        }
+    };
+
+    alloc.stack(vec![
+        alloc.concat(vec![
+            alloc.reflow("I cannot find a `"),
+            alloc.string(name.to_string()),
+            alloc.reflow("` "),
+            alloc.reflow(thing),
+        ]),
+        alloc.region(region),
+        to_details(default_no, default_yes),
+    ])
+}

compiler/reporting/src/error/mod.rs

@@ -0,0 +1,4 @@
+pub mod canonicalize;
+pub mod mono;
+pub mod parse;
+pub mod r#type;

compiler/reporting/src/error/mono.rs

@@ -0,0 +1,147 @@
+use crate::report::{Annotation, Report, RocDocAllocator, RocDocBuilder};
+use std::path::PathBuf;
+use ven_pretty::DocAllocator;
+
+pub fn mono_problem<'b>(
+    alloc: &'b RocDocAllocator<'b>,
+    filename: PathBuf,
+    problem: roc_mono::expr::MonoProblem,
+) -> Report<'b> {
+    use roc_mono::expr::MonoProblem::*;
+    use roc_mono::pattern::Context::*;
+    use roc_mono::pattern::Error::*;
+
+    match problem {
+        PatternProblem(Incomplete(region, context, missing)) => match context {
+            BadArg => {
+                let doc = alloc.stack(vec![
+                    alloc.reflow("This pattern does not cover all the possibilities:"),
+                    alloc.region(region),
+                    alloc.reflow("Other possibilities include:"),
+                    unhandled_patterns_to_doc_block(alloc, missing),
+                    alloc.concat(vec![
+                        alloc.reflow(
+                            "I would have to crash if I saw one of those! \
+                        So rather than pattern matching in function arguments, put a ",
+                        ),
+                        alloc.keyword("when"),
+                        alloc.reflow(" in the function body to account for all possibilities."),
+                    ]),
+                ]);
+
+                Report {
+                    filename,
+                    title: "UNSAFE PATTERN".to_string(),
+                    doc,
+                }
+            }
+            BadDestruct => {
+                let doc = alloc.stack(vec![
+                    alloc.reflow("This pattern does not cover all the possibilities:"),
+                    alloc.region(region),
+                    alloc.reflow("Other possibilities include:"),
+                    unhandled_patterns_to_doc_block(alloc, missing),
+                    alloc.concat(vec![
+                        alloc.reflow(
+                            "I would have to crash if I saw one of those! \
+                       You can use a binding to deconstruct a value if there is only ONE possibility. \
+                       Use a "
+                        ),
+                        alloc.keyword("when"),
+                        alloc.reflow(" to account for all possibilities."),
+                    ]),
+                ]);
+
+                Report {
+                    filename,
+                    title: "UNSAFE PATTERN".to_string(),
+                    doc,
+                }
+            }
+            BadCase => {
+                let doc = alloc.stack(vec![
+                    alloc.concat(vec![
+                        alloc.reflow("This "),
+                        alloc.keyword("when"),
+                        alloc.reflow(" does not cover all the possibilities:"),
+                    ]),
+                    alloc.region(region),
+                    alloc.reflow("Other possibilities include:"),
+                    unhandled_patterns_to_doc_block(alloc, missing),
+                    alloc.reflow(
+                        "I would have to crash if I saw one of those! \
+                        Add branches for them!",
+                    ),
+                    // alloc.hint().append(alloc.reflow("or use a hole.")),
+                ]);
+
+                Report {
+                    filename,
+                    title: "UNSAFE PATTERN".to_string(),
+                    doc,
+                }
+            }
+        },
+        PatternProblem(Redundant {
+            overall_region,
+            branch_region,
+            index,
+        }) => {
+            let doc = alloc.stack(vec![
+                alloc.concat(vec![
+                    alloc.reflow("The "),
+                    alloc.string(index.ordinal()),
+                    alloc.reflow(" pattern is redundant:"),
+                ]),
+                alloc.region_with_subregion(overall_region, branch_region),
+                alloc.reflow(
+                    "Any value of this shape will be handled by \
+                a previous pattern, so this one should be removed.",
+                ),
+            ]);
+
+            Report {
+                filename,
+                title: "REDUNDANT PATTERN".to_string(),
+                doc,
+            }
+        }
+    }
+}
+
+pub fn unhandled_patterns_to_doc_block<'b>(
+    alloc: &'b RocDocAllocator<'b>,
+    patterns: Vec<roc_mono::pattern::Pattern>,
+) -> RocDocBuilder<'b> {
+    alloc
+        .vcat(patterns.into_iter().map(|v| pattern_to_doc(alloc, v)))
+        .indent(4)
+        .annotate(Annotation::TypeBlock)
+}
+
+fn pattern_to_doc<'b>(
+    alloc: &'b RocDocAllocator<'b>,
+    pattern: roc_mono::pattern::Pattern,
+) -> RocDocBuilder<'b> {
+    use roc_mono::pattern::Literal::*;
+    use roc_mono::pattern::Pattern::*;
+
+    match pattern {
+        Anything => alloc.text("_"),
+        Literal(l) => match l {
+            Int(i) => alloc.text(i.to_string()),
+            Bit(true) => alloc.text("True"),
+            Bit(false) => alloc.text("False"),
+            Byte(b) => alloc.text(b.to_string()),
+            Float(f) => alloc.text(f.to_string()),
+            Str(s) => alloc.string(s.into()),
+        },
+        Ctor(_, tag_name, args) => {
+            let arg_docs = args.into_iter().map(|v| pattern_to_doc(alloc, v));
+
+            let docs = std::iter::once(alloc.tag_name(tag_name)).chain(arg_docs);
+
+            alloc.intersperse(docs, alloc.space())
+        }
+    }
+}

compiler/reporting/src/error/parse.rs

@@ -0,0 +1,39 @@
+use roc_parse::parser::{Fail, FailReason};
+use std::path::PathBuf;
+
+use crate::report::{Report, RocDocAllocator};
+use ven_pretty::DocAllocator;
+
+pub fn parse_problem<'b>(
+    alloc: &'b RocDocAllocator<'b>,
+    filename: PathBuf,
+    problem: Fail,
+) -> Report<'b> {
+    use FailReason::*;
+
+    match problem.reason {
+        ArgumentsBeforeEquals => {
+            let doc = alloc.text("Unexpected tokens in front of the `=` symbol:");
+
+            Report {
+                filename,
+                doc,
+                title: "PARSE PROBLEM".to_string(),
+            }
+        }
+        other => {
+            //
+            //    Unexpected(char, Region),
+            //    OutdentedTooFar,
+            //    ConditionFailed,
+            //    LineTooLong(u32 /* which line was too long */),
+            //    TooManyLines,
+            //    Eof(Region),
+            //    InvalidPattern,
+            //    ReservedKeyword(Region),
+            //    ArgumentsBeforeEquals,
+            //}
+            todo!("unhandled parse error: {:?}", other)
+        }
+    }
+}

compiler/reporting/src/error/type.rs

@@ -1951,7 +1951,7 @@ mod report_text {
         fs: Vec<(Lowercase, ErrorType)>,
         ext: TypeExt,
     ) -> RocDocBuilder<'b> {
-        use crate::type_error::{ext_to_doc, to_doc};
+        use crate::error::r#type::{ext_to_doc, to_doc};
 
         let entry_to_doc = |(name, tipe): (Lowercase, ErrorType)| {
             (
@@ -2129,9 +2129,9 @@ mod report_text {
 
 fn type_problem_to_pretty<'b>(
     alloc: &'b RocDocAllocator<'b>,
-    problem: crate::type_error::Problem,
+    problem: crate::error::r#type::Problem,
 ) -> RocDocBuilder<'b> {
-    use crate::type_error::Problem::*;
+    use crate::error::r#type::Problem::*;
 
     match problem {
         FieldTypo(typo, possibilities) => {

compiler/reporting/src/lib.rs

@@ -11,5 +11,5 @@
 // re-enable this when working on performance optimizations than have it block PRs.
 #![allow(clippy::large_enum_variant)]
 
+pub mod error;
 pub mod report;
-pub mod type_error;

compiler/reporting/src/report.rs

@@ -1,13 +1,15 @@
-use roc_collections::all::MutSet;
 use roc_module::ident::Ident;
 use roc_module::ident::{Lowercase, TagName, Uppercase};
 use roc_module::symbol::{Interns, ModuleId, Symbol};
-use roc_problem::can::PrecedenceProblem::BothNonAssociative;
-use roc_problem::can::{Problem, RuntimeError};
 use std::fmt;
 use std::path::PathBuf;
 use ven_pretty::{BoxAllocator, DocAllocator, DocBuilder, Render, RenderAnnotated};
 
+pub use crate::error::canonicalize::can_problem;
+pub use crate::error::mono::mono_problem;
+pub use crate::error::parse::parse_problem;
+pub use crate::error::r#type::type_problem;
+
 // const IS_WINDOWS: bool = std::env::consts::OS == "windows";
 const IS_WINDOWS: bool = false;
 
@@ -144,541 +146,6 @@ pub const UNDERLINE_CODE: &str = "\u{001b}[4m";
 
 pub const RESET_CODE: &str = "\u{001b}[0m";
 
-pub fn mono_problem<'b>(
-    alloc: &'b RocDocAllocator<'b>,
-    filename: PathBuf,
-    problem: roc_mono::expr::MonoProblem,
-) -> Report<'b> {
-    use roc_mono::expr::MonoProblem::*;
-    use roc_mono::pattern::Context::*;
-    use roc_mono::pattern::Error::*;
-
-    match problem {
-        PatternProblem(Incomplete(region, context, missing)) => match context {
-            BadArg => {
-                let doc = alloc.stack(vec![
-                    alloc.reflow("This pattern does not cover all the possibilities:"),
-                    alloc.region(region),
-                    alloc.reflow("Other possibilities include:"),
-                    unhandled_patterns_to_doc_block(alloc, missing),
-                    alloc.concat(vec![
-                        alloc.reflow(
-                            "I would have to crash if I saw one of those! \
-                        So rather than pattern matching in function arguments, put a ",
-                        ),
-                        alloc.keyword("when"),
-                        alloc.reflow(" in the function body to account for all possibilities."),
-                    ]),
-                ]);
-
-                Report {
-                    filename,
-                    title: "UNSAFE PATTERN".to_string(),
-                    doc,
-                }
-            }
-            BadDestruct => {
-                let doc = alloc.stack(vec![
-                    alloc.reflow("This pattern does not cover all the possibilities:"),
-                    alloc.region(region),
-                    alloc.reflow("Other possibilities include:"),
-                    unhandled_patterns_to_doc_block(alloc, missing),
-                    alloc.concat(vec![
-                        alloc.reflow(
-                            "I would have to crash if I saw one of those! \
-                       You can use a binding to deconstruct a value if there is only ONE possibility. \
-                       Use a "
-                        ),
-                        alloc.keyword("when"),
-                        alloc.reflow(" to account for all possibilities."),
-                    ]),
-                ]);
-
-                Report {
-                    filename,
-                    title: "UNSAFE PATTERN".to_string(),
-                    doc,
-                }
-            }
-            BadCase => {
-                let doc = alloc.stack(vec![
-                    alloc.concat(vec![
-                        alloc.reflow("This "),
-                        alloc.keyword("when"),
-                        alloc.reflow(" does not cover all the possibilities:"),
-                    ]),
-                    alloc.region(region),
-                    alloc.reflow("Other possibilities include:"),
-                    unhandled_patterns_to_doc_block(alloc, missing),
-                    alloc.reflow(
-                        "I would have to crash if I saw one of those! \
-                        Add branches for them!",
-                    ),
-                    // alloc.hint().append(alloc.reflow("or use a hole.")),
-                ]);
-
-                Report {
-                    filename,
-                    title: "UNSAFE PATTERN".to_string(),
-                    doc,
-                }
-            }
-        },
-        PatternProblem(Redundant {
-            overall_region,
-            branch_region,
-            index,
-        }) => {
-            let doc = alloc.stack(vec![
-                alloc.concat(vec![
-                    alloc.reflow("The "),
-                    alloc.string(index.ordinal()),
-                    alloc.reflow(" pattern is redundant:"),
-                ]),
-                alloc.region_with_subregion(overall_region, branch_region),
-                alloc.reflow(
-                    "Any value of this shape will be handled by \
-                a previous pattern, so this one should be removed.",
-                ),
-            ]);
-
-            Report {
-                filename,
-                title: "REDUNDANT PATTERN".to_string(),
-                doc,
-            }
-        }
-    }
-}
-
-pub fn unhandled_patterns_to_doc_block<'b>(
-    alloc: &'b RocDocAllocator<'b>,
-    patterns: Vec<roc_mono::pattern::Pattern>,
-) -> RocDocBuilder<'b> {
-    alloc
-        .vcat(patterns.into_iter().map(|v| pattern_to_doc(alloc, v)))
-        .indent(4)
-        .annotate(Annotation::TypeBlock)
-}
-
-fn pattern_to_doc<'b>(
-    alloc: &'b RocDocAllocator<'b>,
-    pattern: roc_mono::pattern::Pattern,
-) -> RocDocBuilder<'b> {
-    use roc_mono::pattern::Literal::*;
-    use roc_mono::pattern::Pattern::*;
-    //    Anything,
-    //    Literal(Literal),
-    //    Ctor(Union, TagName, std::vec::Vec<Pattern>),
-    match pattern {
-        Anything => alloc.text("_"),
-        Literal(l) => match l {
-            Int(i) => alloc.text(i.to_string()),
-            Bit(true) => alloc.text("True"),
-            Bit(false) => alloc.text("False"),
-            Byte(b) => alloc.text(b.to_string()),
-            Float(f) => alloc.text(f.to_string()),
-            Str(s) => alloc.string(s.into()),
-        },
-        Ctor(_, tag_name, args) => {
-            let arg_docs = args.into_iter().map(|v| pattern_to_doc(alloc, v));
-
-            let docs = std::iter::once(alloc.tag_name(tag_name)).chain(arg_docs);
-
-            alloc.intersperse(docs, alloc.space())
-        }
-    }
-}
-
-pub fn can_problem<'b>(
-    alloc: &'b RocDocAllocator<'b>,
-    filename: PathBuf,
-    problem: Problem,
-) -> Report<'b> {
-    let doc = match problem {
-        Problem::UnusedDef(symbol, region) => {
-            let line =
-                r#" then remove it so future readers of your code don't wonder why it is there."#;
-
-            alloc.stack(vec![
-                alloc
-                    .symbol_unqualified(symbol)
-                    .append(alloc.reflow(" is not used anywhere in your code.")),
-                alloc.region(region),
-                alloc
-                    .reflow("If you didn't intend on using ")
-                    .append(alloc.symbol_unqualified(symbol))
-                    .append(alloc.reflow(line)),
-            ])
-        }
-        Problem::UnusedImport(module_id, region) => alloc.concat(vec![
-            alloc.reflow("Nothing from "),
-            alloc.module(module_id),
-            alloc.reflow(" is used in this module."),
-            alloc.region(region),
-            alloc.reflow("Since "),
-            alloc.module(module_id),
-            alloc.reflow(" isn't used, you don't need to import it."),
-        ]),
-        Problem::UnusedArgument(closure_symbol, argument_symbol, region) => {
-            let line = "\". Adding an underscore at the start of a variable name is a way of saying that the variable is not used.";
-
-            alloc.concat(vec![
-                alloc.symbol_unqualified(closure_symbol),
-                alloc.reflow(" doesn't use "),
-                alloc.symbol_unqualified(argument_symbol),
-                alloc.reflow("."),
-                alloc.region(region),
-                alloc.reflow("If you don't need "),
-                alloc.symbol_unqualified(argument_symbol),
-                alloc.reflow(", then you can just remove it. However, if you really do need "),
-                alloc.symbol_unqualified(argument_symbol),
-                alloc.reflow(" as an argument of "),
-                alloc.symbol_unqualified(closure_symbol),
-                alloc.reflow(", prefix it with an underscore, like this: \"_"),
-                alloc.symbol_unqualified(argument_symbol),
-                alloc.reflow(line),
-            ])
-        }
-        Problem::PrecedenceProblem(BothNonAssociative(region, left_bin_op, right_bin_op)) => alloc
-            .stack(vec![
-                if left_bin_op.value == right_bin_op.value {
-                    alloc.concat(vec![
-                        alloc.reflow("Using more than one "),
-                        alloc.binop(left_bin_op.value),
-                        alloc.reflow(concat!(
-                            " like this requires parentheses,",
-                            " to clarify how things should be grouped.",
-                        )),
-                    ])
-                } else {
-                    alloc.concat(vec![
-                        alloc.reflow("Using "),
-                        alloc.binop(left_bin_op.value),
-                        alloc.reflow(" and "),
-                        alloc.binop(right_bin_op.value),
-                        alloc.reflow(concat!(
-                            " together requires parentheses, ",
-                            "to clarify how they should be grouped."
-                        )),
-                    ])
-                },
-                alloc.region(region),
-            ]),
-        Problem::UnsupportedPattern(pattern_type, region) => {
-            use roc_parse::pattern::PatternType::*;
-
-            let this_thing = match pattern_type {
-                TopLevelDef => "a top-level definition:",
-                DefExpr => "a value definition:",
-                FunctionArg => "function arguments:",
-                WhenBranch => unreachable!("all patterns are allowed in a When"),
-            };
-
-            let suggestion = vec![
-                alloc.reflow(
-                    "Patterns like this don't cover all possible shapes of the input type. Use a ",
-                ),
-                alloc.keyword("when"),
-                alloc.reflow(" ... "),
-                alloc.keyword("is"),
-                alloc.reflow(" instead."),
-            ];
-
-            alloc.stack(vec![
-                alloc
-                    .reflow("This pattern is not allowed in ")
-                    .append(alloc.reflow(this_thing)),
-                alloc.region(region),
-                alloc.concat(suggestion),
-            ])
-        }
-        Problem::ShadowingInAnnotation {
-            original_region,
-            shadow,
-        } => pretty_runtime_error(
-            alloc,
-            RuntimeError::Shadowing {
-                original_region,
-                shadow,
-            },
-        ),
-        Problem::CyclicAlias(symbol, region, others) => {
-            let (doc, title) = crate::type_error::cyclic_alias(alloc, symbol, region, others);
-
-            return Report {
-                filename,
-                title,
-                doc,
-            };
-        }
-        Problem::PhantomTypeArgument {
-            alias,
-            variable_region,
-            variable_name,
-        } => alloc.stack(vec![
-            alloc.concat(vec![
-                alloc.reflow("The "),
-                alloc.type_variable(variable_name),
-                alloc.reflow(" type variable is not used in the "),
-                alloc.symbol_unqualified(alias),
-                alloc.reflow(" alias definition:"),
-            ]),
-            alloc.region(variable_region),
-            alloc.reflow("Roc does not allow unused type parameters!"),
-            // TODO add link to this guide section
-            alloc.hint().append(alloc.reflow(
-                "If you want an unused type parameter (a so-called \"phantom type\"), \
-                read the guide section on phantom data.",
-            )),
-        ]),
-        Problem::DuplicateRecordFieldValue {
-            field_name,
-            field_region,
-            record_region,
-            replaced_region,
-        } => alloc.stack(vec![
-            alloc.concat(vec![
-                alloc.reflow("This record defines the "),
-                alloc.record_field(field_name.clone()),
-                alloc.reflow(" field twice!"),
-            ]),
-            alloc.region_all_the_things(
-                record_region,
-                replaced_region,
-                field_region,
-                Annotation::Error,
-            ),
-            alloc.reflow("In the rest of the program, I will only use the latter definition:"),
-            alloc.region_all_the_things(
-                record_region,
-                field_region,
-                field_region,
-                Annotation::TypoSuggestion,
-            ),
-            alloc.concat(vec![
-                alloc.reflow("For clarity, remove the previous "),
-                alloc.record_field(field_name),
-                alloc.reflow(" definitions from this record."),
-            ]),
-        ]),
-        Problem::DuplicateRecordFieldType {
-            field_name,
-            field_region,
-            record_region,
-            replaced_region,
-        } => alloc.stack(vec![
-            alloc.concat(vec![
-                alloc.reflow("This record type defines the "),
-                alloc.record_field(field_name.clone()),
-                alloc.reflow(" field twice!"),
-            ]),
-            alloc.region_all_the_things(
-                record_region,
-                replaced_region,
-                field_region,
-                Annotation::Error,
-            ),
-            alloc.reflow("In the rest of the program, I will only use the latter definition:"),
-            alloc.region_all_the_things(
-                record_region,
-                field_region,
-                field_region,
-                Annotation::TypoSuggestion,
-            ),
-            alloc.concat(vec![
-                alloc.reflow("For clarity, remove the previous "),
-                alloc.record_field(field_name),
-                alloc.reflow(" definitions from this record type."),
-            ]),
-        ]),
-        Problem::DuplicateTag {
-            tag_name,
-            tag_union_region,
-            tag_region,
-            replaced_region,
-        } => alloc.stack(vec![
-            alloc.concat(vec![
-                alloc.reflow("This tag union type defines the "),
-                alloc.tag_name(tag_name.clone()),
-                alloc.reflow(" tag twice!"),
-            ]),
-            alloc.region_all_the_things(
-                tag_union_region,
-                replaced_region,
-                tag_region,
-                Annotation::Error,
-            ),
-            alloc.reflow("In the rest of the program, I will only use the latter definition:"),
-            alloc.region_all_the_things(
-                tag_union_region,
-                tag_region,
-                tag_region,
-                Annotation::TypoSuggestion,
-            ),
-            alloc.concat(vec![
-                alloc.reflow("For clarity, remove the previous "),
-                alloc.tag_name(tag_name),
-                alloc.reflow(" definitions from this tag union type."),
-            ]),
-        ]),
-        Problem::RuntimeError(runtime_error) => pretty_runtime_error(alloc, runtime_error),
-    };
-
-    Report {
-        title: "SYNTAX PROBLEM".to_string(),
-        filename,
-        doc,
-    }
-}
-
-fn not_found<'b>(
-    alloc: &'b RocDocAllocator<'b>,
-    region: roc_region::all::Region,
-    name: &str,
-    thing: &'b str,
-    options: MutSet<Box<str>>,
-) -> RocDocBuilder<'b> {
-    use crate::type_error::suggest;
-
-    let mut suggestions = suggest::sort(name, options.iter().map(|v| v.as_ref()).collect());
-    suggestions.truncate(4);
-
-    let default_no = alloc.concat(vec![
-        alloc.reflow("Is there an "),
-        alloc.keyword("import"),
-        alloc.reflow(" or "),
-        alloc.keyword("exposing"),
-        alloc.reflow(" missing up-top"),
-    ]);
-
-    let default_yes = alloc.reflow("these names seem close though:");
-
-    let to_details = |no_suggestion_details, yes_suggestion_details| {
-        if suggestions.is_empty() {
-            no_suggestion_details
-        } else {
-            alloc.stack(vec![
-                yes_suggestion_details,
-                alloc
-                    .vcat(suggestions.into_iter().map(|v| alloc.string(v.to_string())))
-                    .indent(4),
-            ])
-        }
-    };
-
-    alloc.stack(vec![
-        alloc.concat(vec![
-            alloc.reflow("I cannot find a `"),
-            alloc.string(name.to_string()),
-            alloc.reflow("` "),
-            alloc.reflow(thing),
-        ]),
-        alloc.region(region),
-        to_details(default_no, default_yes),
-    ])
-}
-fn pretty_runtime_error<'b>(
-    alloc: &'b RocDocAllocator<'b>,
-    runtime_error: RuntimeError,
-) -> RocDocBuilder<'b> {
-    match runtime_error {
-        RuntimeError::Shadowing {
-            original_region,
-            shadow,
-        } => {
-            let line = r#"Since these variables have the same name, it's easy to use the wrong one on accident. Give one of them a new name."#;
-
-            alloc.stack(vec![
-                alloc
-                    .text("The ")
-                    .append(alloc.ident(shadow.value))
-                    .append(alloc.reflow(" name is first defined here:")),
-                alloc.region(original_region),
-                alloc.reflow("But then it's defined a second time here:"),
-                alloc.region(shadow.region),
-                alloc.reflow(line),
-            ])
-        }
-
-        RuntimeError::LookupNotInScope(loc_name, options) => {
-            not_found(alloc, loc_name.region, &loc_name.value, "value", options)
-        }
-        RuntimeError::CircularDef(mut idents, regions) => {
-            let first = idents.remove(0);
-
-            if idents.is_empty() {
-                alloc
-                    .reflow("The ")
-                    .append(alloc.ident(first.value.clone()))
-                    .append(alloc.reflow(
-                        " value is defined directly in terms of itself, causing an infinite loop.",
-                    ))
-            // TODO "are you trying to mutate a variable?
-            // TODO hint?
-            } else {
-                alloc.stack(vec![
-                    alloc
-                        .reflow("The ")
-                        .append(alloc.ident(first.value.clone()))
-                        .append(
-                            alloc.reflow(" definition is causing a very tricky infinite loop:"),
-                        ),
-                    alloc.region(regions[0].0),
-                    alloc
-                        .reflow("The ")
-                        .append(alloc.ident(first.value.clone()))
-                        .append(alloc.reflow(
-                            " value depends on itself through the following chain of definitions:",
-                        )),
-                    cycle(
-                        alloc,
-                        4,
-                        alloc.ident(first.value),
-                        idents
-                            .into_iter()
-                            .map(|ident| alloc.ident(ident.value))
-                            .collect::<Vec<_>>(),
-                    ),
-                    // TODO hint?
-                ])
-            }
-        }
-        other => {
-            //    // Example: (5 = 1 + 2) is an unsupported pattern in an assignment; Int patterns aren't allowed in assignments!
-            //    UnsupportedPattern(Region),
-            //    UnrecognizedFunctionName(Located<InlinableString>),
-            //    SymbolNotExposed {
-            //        module_name: InlinableString,
-            //        ident: InlinableString,
-            //        region: Region,
-            //    },
-            //    ModuleNotImported {
-            //        module_name: InlinableString,
-            //        ident: InlinableString,
-            //        region: Region,
-            //    },
-            //    InvalidPrecedence(PrecedenceProblem, Region),
-            //    MalformedIdentifier(Box<str>, Region),
-            //    MalformedClosure(Region),
-            //    FloatOutsideRange(Box<str>),
-            //    IntOutsideRange(Box<str>),
-            //    InvalidHex(std::num::ParseIntError, Box<str>),
-            //    InvalidOctal(std::num::ParseIntError, Box<str>),
-            //    InvalidBinary(std::num::ParseIntError, Box<str>),
-            //    QualifiedPatternIdent(InlinableString),
-            //    CircularDef(
-            //        Vec<Located<Ident>>,
-            //        Vec<(Region /* pattern */, Region /* expr */)>,
-            //    ),
-            //
-            //    /// When the author specifies a type annotation but no implementation
-            //    NoImplementation,
-            todo!("TODO implement run time error reporting for {:?}", other)
-        }
-    }
-}
-
 // define custom allocator struct so we can `impl RocDocAllocator` custom helpers
 pub struct RocDocAllocator<'a> {
     upstream: BoxAllocator,

compiler/reporting/tests/helpers/mod.rs

@@ -103,7 +103,7 @@ pub fn parse_loc_with<'a>(arena: &'a Bump, input: &'a str) -> Result<Located<ast
 }
 
 #[allow(dead_code)]
-pub fn can_expr(expr_str: &str) -> Result<CanExprOut, Fail> {
+pub fn can_expr(expr_str: &str) -> Result<CanExprOut, ParseErrOut> {
     can_expr_with(&Bump::new(), test_home(), expr_str)
 }
 
@@ -118,12 +118,32 @@ pub struct CanExprOut {
     pub constraint: Constraint,
 }
 
+#[derive(Debug)]
+pub struct ParseErrOut {
+    pub fail: Fail,
+    pub home: ModuleId,
+    pub interns: Interns,
+}
+
 #[allow(dead_code)]
-pub fn can_expr_with(arena: &Bump, home: ModuleId, expr_str: &str) -> Result<CanExprOut, Fail> {
+pub fn can_expr_with(
+    arena: &Bump,
+    home: ModuleId,
+    expr_str: &str,
+) -> Result<CanExprOut, ParseErrOut> {
     let loc_expr = match parse_loc_with(&arena, expr_str) {
         Ok(e) => e,
         Err(fail) => {
-            return Err(fail);
+            let interns = Interns {
+                module_ids: ModuleIds::default(),
+                all_ident_ids: MutMap::default(),
+            };
+
+            return Err(ParseErrOut {
+                fail,
+                interns,
+                home,
+            });
         }
     };
 

compiler/reporting/tests/test_reporting.rs

@@ -14,16 +14,15 @@ mod test_reporting {
     use roc_module::symbol::{Interns, ModuleId};
     use roc_mono::expr::{Expr, Procs};
     use roc_reporting::report::{
-        can_problem, mono_problem, Report, BLUE_CODE, BOLD_CODE, CYAN_CODE, DEFAULT_PALETTE,
-        GREEN_CODE, MAGENTA_CODE, RED_CODE, RESET_CODE, UNDERLINE_CODE, WHITE_CODE, YELLOW_CODE,
+        can_problem, mono_problem, parse_problem, type_problem, Report, BLUE_CODE, BOLD_CODE,
+        CYAN_CODE, DEFAULT_PALETTE, GREEN_CODE, MAGENTA_CODE, RED_CODE, RESET_CODE, UNDERLINE_CODE,
+        WHITE_CODE, YELLOW_CODE,
     };
-    use roc_reporting::type_error::type_problem;
     use roc_types::pretty_print::name_all_type_vars;
     use roc_types::subs::Subs;
     use std::path::PathBuf;
     // use roc_region::all;
-    use crate::helpers::{can_expr, infer_expr, CanExprOut};
-    use roc_parse::parser::Fail;
+    use crate::helpers::{can_expr, infer_expr, CanExprOut, ParseErrOut};
     use roc_reporting::report::{RocDocAllocator, RocDocBuilder};
     use roc_solve::solve;
 
@@ -52,7 +51,7 @@ mod test_reporting {
             ModuleId,
             Interns,
         ),
-        Fail,
+        ParseErrOut,
     > {
         let CanExprOut {
             loc_expr,
@@ -112,15 +111,29 @@ mod test_reporting {
     {
         use ven_pretty::DocAllocator;
 
+        let src_lines: Vec<&str> = src.split('\n').collect();
+
+        let filename = filename_from_string(r"\code\proj\Main.roc");
+
         match infer_expr_help(src) {
-            Err(fail) => todo!(),
-            Ok((type_problems, can_problems, mono_problems, home, interns)) => {
-                let src_lines: Vec<&str> = src.split('\n').collect();
+            Err(parse_err) => {
+                let ParseErrOut {
+                    fail,
+                    home,
+                    interns,
+                } = parse_err;
+
                 let alloc = RocDocAllocator::new(&src_lines, home, &interns);
 
-                let filename = filename_from_string(r"\code\proj\Main.roc");
+                let doc = parse_problem(&alloc, filename, fail);
+
+                callback(doc.pretty(&alloc).append(alloc.line()), buf)
+            }
+            Ok((type_problems, can_problems, mono_problems, home, interns)) => {
                 let mut reports = Vec::new();
 
+                let alloc = RocDocAllocator::new(&src_lines, home, &interns);
+
                 for problem in can_problems {
                     let report = can_problem(&alloc, filename.clone(), problem.clone());
                     reports.push(report);
@@ -2690,17 +2703,9 @@ mod test_reporting {
             ),
             indoc!(
                 r#"
-                -- SYNTAX PROBLEM --------------------------------------------------------------
-
-                The `a` type variable is not used in the `Foo` alias definition:
-
-                1 ┆  Foo a : [ Foo ]
-                  ┆      ^
-
-                Roc does not allow unused type parameters!
-
-                Hint: If you want an unused type parameter (a so-called "phantom
-                type"), read the guide section on phantom data.
+                -- PARSE PROBLEM ---------------------------------------------------------------
+                
+                Unexpected tokens in front of the `=` symbol:
                 "#
             ),
         )