fix: Skip pattern analysis on type mismatches

Author: ShoyuVanilla

src/tools/rust-analyzer/crates/hir-ty/src/diagnostics/expr.rs

@@ -324,6 +324,9 @@ impl ExprValidator {
             let &Statement::Let { pat, initializer, else_branch: None, .. } = stmt else {
                 continue;
             };
+            if self.infer.type_mismatch_for_pat(pat).is_some() {
+                continue;
+            }
             let Some(initializer) = initializer else { continue };
             let ty = &self.infer[initializer];
             if ty.contains_unknown() {

src/tools/rust-analyzer/crates/ide-diagnostics/src/handlers/type_mismatch.rs

@@ -1243,4 +1243,18 @@ fn foo(v: &Enum) {
     "#,
         );
     }
+
+    #[test]
+    fn regression_19844() {
+        check_diagnostics(
+            r#"
+fn main() {
+    struct S {}
+    enum E { V() }
+    let E::V() = &S {};
+     // ^^^^^^ error: expected S, found E
+}
+"#,
+        );
+    }
 }