Rollup merge of #135833 - lqd:add-ice-test, r=compiler-errors

Add fixme and test for issue #135289
This PR:
- adds a test minimizing issue #135289 for PR #135310
- adds a fixme about the suboptimal fix for the ICE
I've verified the test indeed ICEs with 3f2f695 reverted.
r? `@estebank`

Author: matthiaskrgr

compiler/rustc_mir_build/src/thir/pattern/check_match.rs

@@ -1086,6 +1086,12 @@ fn find_fallback_pattern_typo<'tcx>(
 let vis = cx.tcx.visibility(item.owner_id);
 if vis.is_accessible_from(parent, cx.tcx){
  accessible.push(item_name);
+// FIXME: the line below from PR #135310 is a workaround for the ICE in issue
+// #135289, where a macro in a dependency can create unreachable patterns in the
+// current crate. Path trimming expects diagnostics for a typoed const, but no
+// diagnostics are emitted and we ICE. See
+// `tests/ui/resolve/const-with-typo-in-pattern-binding-ice-135289.rs` for a
+// test that reproduces the ICE if we don't use `with_no_trimmed_paths!`.
 let path = with_no_trimmed_paths!(cx.tcx.def_path_str(item.owner_id));
  accessible_path.push(path);
 }elseif name == item_name {

tests/ui/resolve/auxiliary/fake_matches.rs

@@ -0,0 +1,13 @@
+// Helper for test tests/ui/resolve/const-with-typo-in-pattern-binding-ice-135289.rs
+
+//@ edition: 2018
+
+#[macro_export]
+macro_rules! assert_matches {
+( $e:expr , $($pat:pat)|+ ) => {
+match $e {
+ $($pat)|+ => (),
+ _ => (),
+}
+};
+}

tests/ui/resolve/const-with-typo-in-pattern-binding-ice-135289.rs

@@ -0,0 +1,17 @@
+// This is a non-regression test for issue 135289, where the "const with typo in pattern" diagnostic
+// caused an ICE when unexpectedly pretty printing a type for unreachable arms via a macro defined
+// in a dependency.
+
+#![warn(unreachable_patterns)]// needed to reproduce the ICE described in #135289
+
+//@ check-pass
+//@ aux-build: fake_matches.rs
+externcrate fake_matches;
+
+const _A:u64 = 0;
+pubfnf() -> u64{
+0
+}
+fnmain(){
+ fake_matches::assert_matches!(f(), _non_existent);
+}