Add test for an inference failure.

src/test/run-pass/issue-22066.rs

@@ -0,0 +1,21 @@
+// Copyright 2017 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.
+
+pub trait LineFormatter<'a> {
+    type Iter: Iterator<Item=&'a str> + 'a;
+    fn iter(&'a self, line: &'a str) -> Self::Iter;
+
+    fn dimensions(&'a self, line: &'a str) {
+        let iter: Self::Iter = self.iter(line);
+        <_ as IntoIterator>::into_iter(iter);
+    }
+}
+
+fn main() {}