From e50ce67631bc8f8e28042112a924b73c6081dc71 Mon Sep 17 00:00:00 2001
From: Dawer <7803845+iDawer@users.noreply.github.com>
Date: Thu, 6 May 2021 13:32:35 +0500
Subject: Do not do match check if lowering failed.

---
 crates/hir_ty/src/diagnostics/expr.rs | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/crates/hir_ty/src/diagnostics/expr.rs b/crates/hir_ty/src/diagnostics/expr.rs
index 8f141a308..929c4a9cc 100644
--- a/crates/hir_ty/src/diagnostics/expr.rs
+++ b/crates/hir_ty/src/diagnostics/expr.rs
@@ -388,14 +388,26 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
 
         let pattern_arena = RefCell::new(PatternArena::new());
 
+        let mut have_errors = false;
         let m_arms: Vec<_> = arms
             .iter()
             .map(|arm| usefulness::MatchArm {
-                pat: self.lower_pattern(arm.pat, &mut pattern_arena.borrow_mut(), db, &body),
+                pat: self.lower_pattern(
+                    arm.pat,
+                    &mut pattern_arena.borrow_mut(),
+                    db,
+                    &body,
+                    &mut have_errors,
+                ),
                 has_guard: arm.guard.is_some(),
             })
             .collect();
 
+        // Bail out early if lowering failed.
+        if have_errors {
+            return;
+        }
+
         let cx = usefulness::MatchCheckCtx {
             module: self.owner.module(db.upcast()),
             match_expr,
@@ -442,10 +454,15 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
         pattern_arena: &mut PatternArena,
         db: &dyn HirDatabase,
         body: &Body,
+        have_errors: &mut bool,
     ) -> pattern::PatId {
         let mut patcx = pattern::PatCtxt::new(db, &self.infer, body);
         let pattern = patcx.lower_pattern(pat);
-        pattern_arena.alloc(expand_pattern(pattern))
+        let pattern = pattern_arena.alloc(expand_pattern(pattern));
+        if !patcx.errors.is_empty() {
+            *have_errors = true;
+        }
+        pattern
     }
 
     fn validate_results_in_tail_expr(&mut self, body_id: ExprId, id: ExprId, db: &dyn HirDatabase) {
-- 
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