save-analysis: Add a related test case

src/test/ui/save-analysis/issue-63663.rs

@@ -0,0 +1,23 @@
+// check-pass
+// compile-flags: -Zsave-analysis
+
+// Check that this doesn't ICE when processing associated const in formal
+// argument and return type of functions defined inside function/method scope.
+
+pub trait Trait {
+    type Assoc;
+}
+
+pub struct A;
+
+pub fn func() {
+    fn _inner1<U: Trait>(_: U::Assoc) {}
+    fn _inner2<U: Trait>() -> U::Assoc { unimplemented!() }
+
+    impl A {
+        fn _inner1<U: Trait>(self, _: U::Assoc) {}
+        fn _inner2<U: Trait>(self) -> U::Assoc { unimplemented!() }
+    }
+}
+
+fn main() {}