Add regression test for rust-lang#18661

Author: bkoropoff

src/test/run-pass/issue-18661.rs

@@ -0,0 +1,28 @@
+// 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 param substitutions from the correct environment are
+// used when translating unboxed closure calls.
+
+#![feature(unboxed_closures)]
+
+pub fn inside<F: Fn()>(c: F) {
+    c.call(());
+}
+
+// Use different number of type parameters and closure type to trigger
+// an obvious ICE when param environments are mixed up
+pub fn outside<A,B>() {
+    inside(|&:| {});
+}
+
+fn main() {
+    outside::<(),()>();
+}