test(delegation): Add regression tests for #153743 and #153744

Author: TKanX

tests/ui/delegation/ice-non-fn-target-in-trait-impl.rs

@@ -0,0 +1,20 @@
+// Regression test for #153743 and #153744.
+// Delegation to a module or crate root inside a trait impl
+// should emit a resolution error, not ICE.
+
+#![feature(fn_delegation)]
+#![allow(incomplete_features)]
+
+trait Trait {
+    fn bar();
+    fn bar2();
+}
+
+impl Trait for () {
+    reuse std::path::<> as bar;
+    //~^ ERROR expected function, found module `std::path`
+    reuse core::<> as bar2;
+    //~^ ERROR expected function, found crate `core`
+}
+
+fn main() {}

tests/ui/delegation/ice-non-fn-target-in-trait-impl.stderr

@@ -0,0 +1,15 @@
+error[E0423]: expected function, found module `std::path`
+  --> $DIR/ice-non-fn-target-in-trait-impl.rs:14:11
+   |
+LL |     reuse std::path::<> as bar;
+   |           ^^^^^^^^^^^^^ not a function
+
+error[E0423]: expected function, found crate `core`
+  --> $DIR/ice-non-fn-target-in-trait-impl.rs:16:11
+   |
+LL |     reuse core::<> as bar2;
+   |           ^^^^^^^^ not a function
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0423`.