Add test.

src/test/auxiliary/issue-16643.rs

+// 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.
+
+#![crate_type = "lib"]
+
+pub struct TreeBuilder<H>;
+
+impl<H> TreeBuilder<H> {
+    pub fn process_token(&mut self) {
+        match self {
+            _ => for _y in *self {}
+        }
+    }
+}
+
+impl<H> Iterator<H> for TreeBuilder<H> {
+    fn next(&mut self) -> Option<H> {
+        None
+    }
+}

src/test/run-pass/issue-16643.rs

+// 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.
+
+// aux-build:issue-16643.rs
+
+extern crate i = "issue-16643";
+
+pub fn main() {
+    i::TreeBuilder::<uint>.process_token();
+}