Add regression test for #18685

Author: bkoropoff

src/test/run-pass/issue-18685.rs

@@ -0,0 +1,30 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Test that the self param space is not used in a conflicting
+// manner by unboxed closures within a default method on a trait
+
+#![feature(unboxed_closures, overloaded_calls)]
+
+trait Tr {
+    fn foo(&self);
+
+    fn bar(&self) {
+        (|:| { self.foo() })()
+    }
+}
+
+impl Tr for () {
+    fn foo(&self) {}
+}
+
+fn main() {
+    ().bar();
+}