add test for issue 135289

Author: lqd

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
+extern crate fake_matches;
+
+const _A: u64 = 0;
+pub fn f() -> u64 {
+    0
+}
+fn main() {
+    fake_matches::assert_matches!(f(), _non_existent);
+}