add test for ICE: failed to resolve instance for <fn() -> impl ...> rust-lang#123145

Fixes rust-lang#123145

Author: matthiaskrgr

tests/ui/impl-trait/failed-to-resolve-instance-ice-123145.rs

@@ -0,0 +1,20 @@
+// ICE failed to resolve instance for ...
+// issue: rust-lang/rust#123145
+//@ build-fail
+//~^^^ ERROR overflow evaluating the requirement `(fn() -> impl Handler
+
+trait Handler {
+    fn handle(&self) {}
+}
+
+impl<H: Handler, F: Fn() -> H> Handler for F {}
+
+impl<L: Handler> Handler for (L,) {}
+
+fn one() -> impl Handler {
+    (one,)
+}
+
+fn main() {
+    one.handle();
+}

tests/ui/impl-trait/failed-to-resolve-instance-ice-123145.stderr

@@ -0,0 +1,15 @@
+error[E0275]: overflow evaluating the requirement `(fn() -> impl Handler {one},): Handler`
+   |
+note: required for `fn() -> impl Handler {one}` to implement `Handler`
+  --> $DIR/failed-to-resolve-instance-ice-123145.rs:10:32
+   |
+LL | impl<H: Handler, F: Fn() -> H> Handler for F {}
+   |         -------                ^^^^^^^     ^
+   |         |
+   |         unsatisfied trait bound introduced here
+   = note: 2 redundant requirements hidden
+   = note: required for `fn() -> impl Handler {one}` to implement `Handler`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0275`.