Add test/comment about const patterns with unused params

1 files changed, 19 insertions, 0 deletions

diff --git a/tests/ui/pattern/unused-parameters-const-pattern.rs b/tests/ui/pattern/unused-parameters-const-pattern.rs
new file mode 100644
index 00000000000..107c65ddfd3
--- /dev/null
+++ b/tests/ui/pattern/unused-parameters-const-pattern.rs
@@ -0,0 +1,19 @@
+//@ check-pass
+
+// Tests that const patterns that use generic parameters are
+// allowed if we are still able to evaluate them.
+
+trait Trait { const ASSOC: usize; }
+
+impl<T> Trait for T {
+    const ASSOC: usize = 10;
+}
+
+fn foo<T>(a: usize) {
+    match a {
+        <T as Trait>::ASSOC => (),
+        _ => (),
+    }
+}
+
+fn main() {}