fix: Panic in debug profile for tuple deconstruct with arity mismatch

crates/hir-ty/src/diagnostics/match_check/pat_analysis.rs

@@ -86,6 +86,15 @@ impl<'db> MatchCheckCtx<'db> {
         arms: &[MatchArm<'db>],
         scrut_ty: Ty,
     ) -> Result<UsefulnessReport<'db, Self>, ()> {
+        if scrut_ty.contains_unknown() {
+            return Err(());
+        }
+        for arm in arms {
+            if arm.pat.ty().contains_unknown() {
+                return Err(());
+            }
+        }
+
         // FIXME: Determine place validity correctly. For now, err on the safe side.
         let place_validity = PlaceValidity::MaybeInvalid;
         // Measured to take ~100ms on modern hardware.

crates/ide-diagnostics/src/handlers/type_mismatch.rs

@@ -745,6 +745,18 @@ fn f() {
         0
     }
 }
+"#,
+        );
+    }
+
+    #[test]
+    fn regression_17585() {
+        check_diagnostics(
+            r#"
+fn f() {
+    let (_, _, _, ..) = (true, 42);
+     // ^^^^^^^^^^^^^ error: expected (bool, i32), found (bool, i32, {unknown})
+}
 "#,
         );
     }