From 6e728df43af632996f3f1d786934476b0b2a6412 Mon Sep 17 00:00:00 2001
From: Shoyu Vanilla <modulo641@gmail.com>
Date: Sun, 21 Jul 2024 02:37:14 +0900
Subject: [PATCH] fix: Panic in debug profile for tuple deconstruct with arity
 mismatch

---
 .../src/diagnostics/match_check/pat_analysis.rs      |  9 +++++++++
 crates/ide-diagnostics/src/handlers/type_mismatch.rs | 12 ++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/crates/hir-ty/src/diagnostics/match_check/pat_analysis.rs b/crates/hir-ty/src/diagnostics/match_check/pat_analysis.rs
index 7bf8af4cab..a12e201cf3 100644
--- a/crates/hir-ty/src/diagnostics/match_check/pat_analysis.rs
+++ b/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.
diff --git a/crates/ide-diagnostics/src/handlers/type_mismatch.rs b/crates/ide-diagnostics/src/handlers/type_mismatch.rs
index 4c25532228..4e52d28051 100644
--- a/crates/ide-diagnostics/src/handlers/type_mismatch.rs
+++ b/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})
+}
 "#,
         );
     }