Failing test

tests/ui/symbol-names/normalize-in-param-env.rs

@@ -0,0 +1,38 @@
+//@ revisions: legacy v0
+//@[v0] compile-flags: -C symbol-mangling-version=v0
+//@[legacy] compile-flags: -C symbol-mangling-version=legacy -Zunstable-options
+//@ build-pass
+
+pub struct Vec2;
+
+pub trait Point {
+    type S;
+}
+impl Point for Vec2 {
+    type S = f32;
+}
+
+pub trait Point2: Point<S = Self::S2> {
+    type S2;
+}
+impl Point2 for Vec2 {
+    type S2 = Self::S;
+}
+
+trait MyFrom<T> {
+    fn my_from();
+}
+impl<P: Point2> MyFrom<P::S> for P {
+    fn my_from() {
+        // This is just a really dumb way to force the legacy symbol mangling to
+        // mangle the closure's parent impl def path *with* args. Otherwise,
+        // legacy symbol mangling will strip the args from the instance, meaning
+        // that we don't trigger the bug.
+        let c = || {};
+        let x = Box::new(c) as Box<dyn Fn()>;
+    }
+}
+
+fn main() {
+    <Vec2 as MyFrom<_>>::my_from();
+}