From e2b1c69f7488b942360bb3c398a1c831510d1afc Mon Sep 17 00:00:00 2001
From: Dawer <7803845+iDawer@users.noreply.github.com>
Date: Wed, 19 May 2021 10:57:10 +0500
Subject: Check patterns for type match recursively.

---
 crates/hir_ty/src/diagnostics/expr.rs        | 20 ++++++++++++++++++--
 crates/hir_ty/src/diagnostics/match_check.rs | 12 ++++++++++++
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/crates/hir_ty/src/diagnostics/expr.rs b/crates/hir_ty/src/diagnostics/expr.rs
index a50ad6b09..b9a69b79c 100644
--- a/crates/hir_ty/src/diagnostics/expr.rs
+++ b/crates/hir_ty/src/diagnostics/expr.rs
@@ -311,11 +311,12 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
                 // necessary.
                 //
                 // FIXME we should use the type checker for this.
-                if pat_ty == match_expr_ty
+                if (pat_ty == match_expr_ty
                     || match_expr_ty
                         .as_reference()
                         .map(|(match_expr_ty, ..)| match_expr_ty == pat_ty)
-                        .unwrap_or(false)
+                        .unwrap_or(false))
+                    && types_of_subpatterns_do_match(pat, &cx.body, &infer)
                 {
                     // If we had a NotUsefulMatchArm diagnostic, we could
                     // check the usefulness of each pattern as we added it
@@ -496,6 +497,21 @@ pub fn record_pattern_missing_fields(
     Some((variant_def, missed_fields, exhaustive))
 }
 
+fn types_of_subpatterns_do_match(pat: PatId, body: &Body, infer: &InferenceResult) -> bool {
+    fn walk(pat: PatId, body: &Body, infer: &InferenceResult, has_type_mismatches: &mut bool) {
+        match infer.type_mismatch_for_pat(pat) {
+            Some(_) => *has_type_mismatches = true,
+            None => {
+                body[pat].walk_child_pats(|subpat| walk(subpat, body, infer, has_type_mismatches))
+            }
+        }
+    }
+
+    let mut has_type_mismatches = false;
+    walk(pat, body, infer, &mut has_type_mismatches);
+    !has_type_mismatches
+}
+
 #[cfg(test)]
 mod tests {
     use crate::diagnostics::tests::check_diagnostics;
diff --git a/crates/hir_ty/src/diagnostics/match_check.rs b/crates/hir_ty/src/diagnostics/match_check.rs
index 6ee0529c6..e8dd669bf 100644
--- a/crates/hir_ty/src/diagnostics/match_check.rs
+++ b/crates/hir_ty/src/diagnostics/match_check.rs
@@ -1127,6 +1127,18 @@ fn main() {
         );
     }
 
+    #[test]
+    fn mismatched_types_in_or_patterns() {
+        check_diagnostics(
+            r#"
+fn main() {
+    match false { true | () => {} }
+    match (false,) { (true | (),) => {} }
+}
+"#,
+        );
+    }
+
     #[test]
     fn malformed_match_arm_tuple_enum_missing_pattern() {
         // We are testing to be sure we don't panic here when the match
-- 
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