add test for #99945

Fixes #99945

Author: matthiaskrgr

tests/ui/type-alias-impl-trait/failed-to-normalize-ice-99945.rs

@@ -0,0 +1,36 @@
+// issue: rust-lang/rust#99945
+// ICE Failed to normalize
+
+#![feature(type_alias_impl_trait)]
+
+trait Widget<E> {
+    type State;
+
+    fn make_state(&self) -> Self::State;
+}
+
+impl<E> Widget<E> for () {
+    type State = ();
+
+    fn make_state(&self) -> Self::State {}
+}
+
+struct StatefulWidget<F>(F);
+
+type StateWidget<'a> = impl Widget<&'a ()>;
+
+impl<F: for<'a> Fn(&'a ()) -> StateWidget<'a>> Widget<()> for StatefulWidget<F> {
+    type State = ();
+
+    fn make_state(&self) -> Self::State {}
+}
+
+fn new_stateful_widget<F: for<'a> Fn(&'a ()) -> StateWidget<'a>>(build: F) -> impl Widget<()> {
+    StatefulWidget(build)
+    //~^ ERROR expected generic lifetime parameter, found `'a`
+}
+
+fn main() {
+    new_stateful_widget(|_| ()).make_state();
+    //~^ ERROR mismatched types
+}

tests/ui/type-alias-impl-trait/failed-to-normalize-ice-99945.stderr

@@ -0,0 +1,25 @@
+error[E0308]: mismatched types
+  --> $DIR/failed-to-normalize-ice-99945.rs:34:29
+   |
+LL | type StateWidget<'a> = impl Widget<&'a ()>;
+   |                        ------------------- the expected opaque type
+...
+LL |     new_stateful_widget(|_| ()).make_state();
+   |                             ^^ expected opaque type, found `()`
+   |
+   = note: expected opaque type `StateWidget<'_>`
+                found unit type `()`
+
+error[E0792]: expected generic lifetime parameter, found `'a`
+  --> $DIR/failed-to-normalize-ice-99945.rs:29:5
+   |
+LL | type StateWidget<'a> = impl Widget<&'a ()>;
+   |                  -- this generic parameter must be used with a generic lifetime parameter
+...
+LL |     StatefulWidget(build)
+   |     ^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0308, E0792.
+For more information about an error, try `rustc --explain E0308`.