Merge #8692

8692: Fix panic caused by new Try trait definition r=flodiebold a=flodiebold

The new Try trait definition caused a query cycle for us. This adds recovery for that cycle, but also fixes the cause, which is that we went through the supertraits when resolving `<T as Trait>::Assoc`, which isn't actually necessary. I also rewrote `all_super_trait_refs` to an iterator before I realized what the actual problem was, so I kept that.

Fixes #8686.

Co-authored-by: Florian Diebold <[email protected]>

1 files changed, 38 insertions, 0 deletions

diff --git a/crates/hir_ty/src/tests/regression.rs b/crates/hir_ty/src/tests/regression.rs
index 9cd9f473d..d14f5c9bb 100644
--- a/crates/hir_ty/src/tests/regression.rs
+++ b/crates/hir_ty/src/tests/regression.rs
@@ -1012,3 +1012,41 @@ fn lifetime_from_chalk_during_deref() {
         "#,
     )
 }
+
+#[test]
+fn issue_8686() {
+    check_infer(
+        r#"
+pub trait Try: FromResidual {
+    type Output;
+    type Residual;
+}
+pub trait FromResidual<R = <Self as Try>::Residual> {
+     fn from_residual(residual: R) -> Self;
+}
+
+struct ControlFlow<B, C>;
+impl<B, C> Try for ControlFlow<B, C> {
+    type Output = C;
+    type Residual = ControlFlow<B, !>;
+}
+impl<B, C> FromResidual for ControlFlow<B, C> {
+    fn from_residual(r: ControlFlow<B, !>) -> Self { ControlFlow }
+}
+
+fn test() {
+    ControlFlow::from_residual(ControlFlow::<u32, !>);
+}
+        "#,
+        expect![[r#"
+            144..152 'residual': R
+            365..366 'r': ControlFlow<B, !>
+            395..410 '{ ControlFlow }': ControlFlow<B, C>
+            397..408 'ControlFlow': ControlFlow<B, C>
+            424..482 '{     ...!>); }': ()
+            430..456 'Contro...sidual': fn from_residual<ControlFlow<u32, {unknown}>, ControlFlow<u32, !>>(ControlFlow<u32, !>) -> ControlFlow<u32, {unknown}>
+            430..479 'Contro...2, !>)': ControlFlow<u32, {unknown}>
+            457..478 'Contro...32, !>': ControlFlow<u32, !>
+        "#]],
+    );
+}