Fix invalid rustdoc rendering for FnTy args

src/test/rustdoc/fn-pointer-arg-name.rs

@@ -0,0 +1,15 @@
+// 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.
+
+#![crate_name = "foo"]
+
+// @has foo/fn.f.html
+// @has - '//*[@class="rust fn"]' 'pub fn f(callback: fn(len: usize, foo: u32))'
+pub fn f(callback: fn(len: usize, foo: u32)) {}