rustdoc: Add a test for fixed issue #15347

Closes #15347

src/compiletest/runtest.rs

@@ -1175,6 +1175,7 @@ fn document(config: &Config, props: &TestProps,
                         out_dir.to_str().unwrap().to_string(),
                         testfile.to_str().unwrap().to_string()];
     args.extend(extra_args.iter().cloned());
+    args.extend(split_maybe_args(&props.compile_flags).into_iter());
     let args = ProcArgs {
         prog: config.rustdoc_path.to_str().unwrap().to_string(),
         args: args,

src/test/rustdoc/issue-15347.rs

@@ -0,0 +1,15 @@
+// Copyright 2105 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.
+
+// compile-flags:--no-defaults --passes "collapse-docs" --passes "unindent-comments"
+
+// @has issue_15347/fn.foo.html
+#[doc(hidden)]
+pub fn foo() {}