internal: Record mismatches of pattern types.

crates/hir_ty/src/diagnostics/expr.rs

@@ -211,7 +211,7 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
 
         // FIXME: Due to shortcomings in the current type system implementation, only emit this
         // diagnostic if there are no type mismatches in the containing function.
-        if self.infer.type_mismatches.iter().next().is_some() {
+        if self.infer.expr_type_mismatches().next().is_some() {
             return;
         }
 

crates/hir_ty/src/infer.rs

@@ -137,8 +137,12 @@ pub struct InferenceResult {
     assoc_resolutions: FxHashMap<ExprOrPatId, AssocItemId>,
     diagnostics: Vec<InferenceDiagnostic>,
     pub type_of_expr: ArenaMap<ExprId, Ty>,
+    /// For each pattern record the type it resolves to.
+    ///
+    /// **Note**: When a pattern type is resolved it may still contain
+    /// unresolved or missing subpatterns or subpatterns of mismatched types.
     pub type_of_pat: ArenaMap<PatId, Ty>,
-    pub(super) type_mismatches: ArenaMap<ExprId, TypeMismatch>,
+    type_mismatches: FxHashMap<ExprOrPatId, TypeMismatch>,
     /// Interned Unknown to return references to.
     standard_types: InternedStandardTypes,
 }
@@ -163,7 +167,22 @@ impl InferenceResult {
         self.assoc_resolutions.get(&id.into()).copied()
     }
     pub fn type_mismatch_for_expr(&self, expr: ExprId) -> Option<&TypeMismatch> {
-        self.type_mismatches.get(expr)
+        self.type_mismatches.get(&expr.into())
+    }
+    pub fn type_mismatch_for_pat(&self, pat: PatId) -> Option<&TypeMismatch> {
+        self.type_mismatches.get(&pat.into())
+    }
+    pub fn expr_type_mismatches(&self) -> impl Iterator<Item = (ExprId, &TypeMismatch)> {
+        self.type_mismatches.iter().filter_map(|(expr_or_pat, mismatch)| match *expr_or_pat {
+            ExprOrPatId::ExprId(expr) => Some((expr, mismatch)),
+            _ => None,
+        })
+    }
+    pub fn pat_type_mismatches(&self) -> impl Iterator<Item = (PatId, &TypeMismatch)> {
+        self.type_mismatches.iter().filter_map(|(expr_or_pat, mismatch)| match *expr_or_pat {
+            ExprOrPatId::PatId(pat) => Some((pat, mismatch)),
+            _ => None,
+        })
     }
     pub fn add_diagnostics(
         &self,

crates/hir_ty/src/infer/expr.rs

@@ -42,7 +42,7 @@ impl<'a> InferenceContext<'a> {
         let could_unify = self.unify(&ty, &expected.ty);
         if !could_unify {
             self.result.type_mismatches.insert(
-                tgt_expr,
+                tgt_expr.into(),
                 TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() },
             );
         }
@@ -54,9 +54,10 @@ impl<'a> InferenceContext<'a> {
     pub(super) fn infer_expr_coerce(&mut self, expr: ExprId, expected: &Expectation) -> Ty {
         let ty = self.infer_expr_inner(expr, &expected);
         let ty = if !self.coerce(&ty, &expected.coercion_target()) {
-            self.result
+            self.result.type_mismatches.insert(
-                .type_mismatches
+                expr.into(),
-                .insert(expr, TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() });
+                TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() },
+            );
             // Return actual type when type mismatch.
             // This is needed for diagnostic when return type mismatch.
             ty

crates/hir_ty/src/infer/pat.rs

@@ -10,7 +10,7 @@ use hir_def::{
 };
 use hir_expand::name::Name;
 
-use super::{BindingMode, Expectation, InferenceContext};
+use super::{BindingMode, Expectation, InferenceContext, TypeMismatch};
 use crate::{
     lower::lower_to_chalk_mutability, static_lifetime, Interner, Substitution, Ty, TyBuilder,
     TyExt, TyKind,
@@ -266,7 +266,10 @@ impl<'a> InferenceContext<'a> {
         // use a new type variable if we got error type here
         let ty = self.insert_type_vars_shallow(ty);
         if !self.unify(&ty, expected) {
-            // FIXME record mismatch, we need to change the type of self.type_mismatches for that
+            self.result.type_mismatches.insert(
+                pat.into(),
+                TypeMismatch { expected: expected.clone(), actual: ty.clone() },
+            );
         }
         let ty = self.resolve_ty_as_possible(ty);
         self.write_pat_ty(pat, ty.clone());

crates/hir_ty/src/tests.rs

@@ -130,7 +130,10 @@ fn infer_with_mismatches(content: &str, include_mismatches: bool) -> String {
                 }
                 Err(SyntheticSyntax) => continue,
             };
-            types.push((syntax_ptr, ty));
+            types.push((syntax_ptr.clone(), ty));
+            if let Some(mismatch) = inference_result.type_mismatch_for_pat(pat) {
+                mismatches.push((syntax_ptr, mismatch));
+            }
         }
 
         for (expr, ty) in inference_result.type_of_expr.iter() {

crates/hir_ty/src/tests/patterns.rs

@@ -546,7 +546,9 @@ fn infer_const_pattern() {
             273..276 'Bar': usize
             280..283 'Bar': usize
             200..223: expected (), got Foo
+            211..214: expected (), got Foo
             262..285: expected (), got usize
+            273..276: expected (), got usize
         "#]],
     );
 }
@@ -703,7 +705,7 @@ fn box_pattern() {
 
 #[test]
 fn tuple_ellipsis_pattern() {
-    check_infer(
+    check_infer_with_mismatches(
         r#"
 fn foo(tuple: (u8, i16, f32)) {
     match tuple {
@@ -744,6 +746,8 @@ fn foo(tuple: (u8, i16, f32)) {
             186..200 '{/*too long*/}': ()
             209..210 '_': (u8, i16, f32)
             214..216 '{}': ()
+            136..142: expected (u8, i16, f32), got (u8, i16)
+            170..182: expected (u8, i16, f32), got (u8, i16, f32, _)
         "#]],
     );
 }
@@ -851,3 +855,55 @@ fn f(e: Enum) {
     "#,
     )
 }
+
+#[test]
+fn type_mismatch_in_or_pattern() {
+    check_infer_with_mismatches(
+        r#"
+fn main() {
+    match (false,) {
+        (true | (),) => {}
+        (() | true,) => {}
+        (_ | (),) => {}
+        (() | _,) => {}
+    }
+}
+"#,
+        expect![[r#"
+            10..142 '{     ...   } }': ()
+            16..140 'match ...     }': ()
+            22..30 '(false,)': (bool,)
+            23..28 'false': bool
+            41..53 '(true | (),)': (bool,)
+            42..46 'true': bool
+            42..46 'true': bool
+            42..51 'true | ()': bool
+            49..51 '()': ()
+            57..59 '{}': ()
+            68..80 '(() | true,)': ((),)
+            69..71 '()': ()
+            69..78 '() | true': ()
+            74..78 'true': bool
+            74..78 'true': bool
+            84..86 '{}': ()
+            95..104 '(_ | (),)': (bool,)
+            96..97 '_': bool
+            96..102 '_ | ()': bool
+            100..102 '()': ()
+            108..110 '{}': ()
+            119..128 '(() | _,)': ((),)
+            120..122 '()': ()
+            120..126 '() | _': ()
+            125..126 '_': bool
+            132..134 '{}': ()
+            49..51: expected bool, got ()
+            68..80: expected (bool,), got ((),)
+            69..71: expected bool, got ()
+            69..78: expected bool, got ()
+            100..102: expected bool, got ()
+            119..128: expected (bool,), got ((),)
+            120..122: expected bool, got ()
+            120..126: expected bool, got ()
+        "#]],
+    );
+}