Auto merge of rust-lang#13774 - lowr:fix/no-infer-vars-in-inference-result, r=Veykril

fix: resolve all inference vars in `InferenceResult::assoc_resolutions`

I think this fixes 'rust-lang#13773, ~but still haven't found repro. I'll try finding one so we can have a regression test~.

We should resolve every inference variable in `InferenceResult` after inference is done. We started recording `Substitution`s for each resolved associated items in rust-lang#13725, but failed to do so which causes crash when analyzing source in IDE layer.

Author: bors

crates/hir-ty/src/infer.rs

@@ -535,6 +535,9 @@ impl<'a> InferenceContext<'a> {
         for (_, subst) in result.method_resolutions.values_mut() {
             *subst = table.resolve_completely(subst.clone());
         }
+        for (_, subst) in result.assoc_resolutions.values_mut() {
+            *subst = table.resolve_completely(subst.clone());
+        }
         for adjustment in result.expr_adjustments.values_mut().flatten() {
             adjustment.target = table.resolve_completely(adjustment.target.clone());
         }

crates/ide/src/hover/tests.rs

@@ -4079,6 +4079,37 @@ const FOO$0: f64 = 1.0f64;
     );
 }
 
+#[test]
+fn hover_const_eval_in_generic_trait() {
+    // Doesn't compile, but we shouldn't crash.
+    check(
+        r#"
+trait Trait<T> {
+    const FOO: bool = false;
+}
+struct S<T>(T);
+impl<T> Trait<T> for S<T> {
+    const FOO: bool = true;
+}
+
+fn test() {
+    S::FOO$0;
+}
+"#,
+        expect![[r#"
+            *FOO*
+
+            ```rust
+            test
+            ```
+
+            ```rust
+            const FOO: bool = true
+            ```
+        "#]],
+    );
+}
+
 #[test]
 fn hover_const_pat() {
     check(