parse guarded record patterns

e.g.

    case foo when
        { x: 4 } -> ...
        { x, y } -> ...

src/can/pattern.rs

@@ -329,6 +329,8 @@ fn add_constraints<'a>(
 ) {
     use crate::parse::ast::Pattern::*;
 
+    dbg!(pattern);
+
     match pattern {
         Underscore | Malformed(_) | QualifiedIdentifier(_) => {
             // Neither the _ pattern nor malformed ones add any constraints.
@@ -397,7 +399,7 @@ fn add_constraints<'a>(
                     &loc_pattern.value,
                     scope,
                     loc_pattern.region,
-                    expected,
+                    expected.clone(),
                     state,
                     var_store,
                 );
@@ -421,8 +423,7 @@ fn add_constraints<'a>(
                         &guard.value,
                         scope,
                         guard.region,
-                        // expect the pattern to equal the field
-                        PExpected::NoExpectation(pat_type),
+                        expected,
                         state,
                         var_store,
                     );
@@ -436,6 +437,7 @@ fn add_constraints<'a>(
                 Constraint::Pattern(region, PatternCategory::Record, record_type, expected);
 
             state.constraints.push(record_con);
+            dbg!(&state.constraints);
         }
 
         GlobalTag(_) | PrivateTag(_) | Apply(_, _) | RecordField(_, _) | EmptyRecordLiteral => {

src/parse/mod.rs

@@ -290,7 +290,7 @@ fn expr_to_pattern<'a>(arena: &'a Bump, expr: &Expr<'a>) -> Result<Pattern<'a>,
 
             for loc_assigned_field in loc_assigned_fields {
                 let region = loc_assigned_field.region;
-                let value = assigned_field_to_pattern(arena, &loc_assigned_field.value)?;
+                let value = assigned_expr_field_to_pattern(arena, &loc_assigned_field.value)?;
 
                 loc_patterns.push(Located { region, value });
             }
@@ -331,7 +331,8 @@ fn expr_to_pattern<'a>(arena: &'a Bump, expr: &Expr<'a>) -> Result<Pattern<'a>,
     }
 }
 
-pub fn assigned_field_to_pattern<'a>(
+/// use for expressions like { x: a + b }
+pub fn assigned_expr_field_to_pattern<'a>(
     arena: &'a Bump,
     assigned_field: &AssignedField<'a, Expr<'a>>,
 ) -> Result<Pattern<'a>, Fail> {
@@ -354,11 +355,46 @@ pub fn assigned_field_to_pattern<'a>(
         }
         AssignedField::LabelOnly(name) => Pattern::Identifier(name.value),
         AssignedField::SpaceBefore(nested, spaces) => Pattern::SpaceBefore(
-            arena.alloc(assigned_field_to_pattern(arena, nested)?),
+            arena.alloc(assigned_expr_field_to_pattern(arena, nested)?),
             spaces,
         ),
         AssignedField::SpaceAfter(nested, spaces) => Pattern::SpaceAfter(
-            arena.alloc(assigned_field_to_pattern(arena, nested)?),
+            arena.alloc(assigned_expr_field_to_pattern(arena, nested)?),
+            spaces,
+        ),
+        AssignedField::Malformed(string) => Pattern::Malformed(string),
+    })
+}
+
+/// Used for patterns like { x: Just _ }
+pub fn assigned_pattern_field_to_pattern<'a>(
+    arena: &'a Bump,
+    assigned_field: &AssignedField<'a, Pattern<'a>>,
+) -> Result<Pattern<'a>, Fail> {
+    // the assigned fields always store spaces, but this slice is often empty
+    Ok(match assigned_field {
+        AssignedField::LabeledValue(name, spaces, value) => {
+            let pattern = value.value.clone();
+            let result = arena.alloc(Located {
+                region: value.region,
+                value: pattern,
+            });
+            if spaces.is_empty() {
+                Pattern::RecordField(name.value, result)
+            } else {
+                Pattern::SpaceAfter(
+                    arena.alloc(Pattern::RecordField(name.value, result)),
+                    spaces,
+                )
+            }
+        }
+        AssignedField::LabelOnly(name) => Pattern::Identifier(name.value),
+        AssignedField::SpaceBefore(nested, spaces) => Pattern::SpaceBefore(
+            arena.alloc(assigned_pattern_field_to_pattern(arena, nested)?),
+            spaces,
+        ),
+        AssignedField::SpaceAfter(nested, spaces) => Pattern::SpaceAfter(
+            arena.alloc(assigned_pattern_field_to_pattern(arena, nested)?),
             spaces,
         ),
         AssignedField::Malformed(string) => Pattern::Malformed(string),
@@ -744,15 +780,19 @@ fn underscore_pattern<'a>() -> impl Parser<'a, Pattern<'a>> {
 }
 
 fn record_destructure<'a>(min_indent: u16) -> impl Parser<'a, Pattern<'a>> {
-    map!(
-        collection!(
-            char('{'),
-            loc!(ident_pattern()),
-            char(','),
-            char('}'),
-            min_indent
-        ),
-        Pattern::RecordDestructure
+    then(
+        record!(loc!(pattern(min_indent)), min_indent),
+        move |arena, state, assigned_fields| {
+            let mut patterns = Vec::with_capacity_in(assigned_fields.len(), arena);
+            for assigned_field in assigned_fields {
+                match assigned_pattern_field_to_pattern(arena, &assigned_field.value) {
+                    Ok(pattern) => patterns.push(Located::at(assigned_field.region, pattern)),
+                    Err(e) => return Err((e, state)),
+                }
+            }
+
+            Ok((Pattern::RecordDestructure(patterns), state))
+        },
     )
 }
 
@@ -1269,7 +1309,7 @@ pub fn record_literal<'a>(min_indent: u16) -> impl Parser<'a, Expr<'a>> {
 
                 for loc_assigned_field in assigned_fields {
                     let region = loc_assigned_field.region;
-                    match assigned_field_to_pattern(arena, &loc_assigned_field.value) {
+                    match assigned_expr_field_to_pattern(arena, &loc_assigned_field.value) {
                         Ok(value) => loc_patterns.push(Located { region, value }),
                         // an Expr became a pattern that should not be.
                         Err(e) => return Err((e, state)),
@@ -1304,7 +1344,7 @@ pub fn record_literal<'a>(min_indent: u16) -> impl Parser<'a, Expr<'a>> {
 
                 for loc_assigned_field in assigned_fields {
                     let region = loc_assigned_field.region;
-                    match assigned_field_to_pattern(arena, &loc_assigned_field.value) {
+                    match assigned_expr_field_to_pattern(arena, &loc_assigned_field.value) {
                         Ok(value) => loc_patterns.push(Located { region, value }),
                         // an Expr became a pattern that should not be.
                         Err(e) => return Err((e, state)),

tests/test_infer.rs

@@ -956,7 +956,22 @@ mod test_infer {
             indoc!(
                 r#"
                 case { x : 4 , y : 3.14 } when
+                    { x: 4 } -> x
                     { x, y } -> x
+                    { y } -> 42
+            "#
+            ),
+            "Int",
+        );
+    }
+
+    #[test]
+    fn record_pattern_match_infer() {
+        infer_eq(
+            indoc!(
+                r#"
+                case foo when
+                    {x:4}-> x
             "#
             ),
             "Int",