rustc: Crawl static initializers for reachability

This ensures that private functions exported through static initializers will
actually end up being public in the object file (so other objects can continue
to reference the function).

Closes #13620

src/librustc/middle/reachable.rs

@@ -270,11 +270,12 @@ fn propagate_node(&mut self, node: &ast_map::Node,
 
                     // Statics with insignificant addresses are not reachable
                     // because they're inlined specially into all other crates.
-                    ast::ItemStatic(..) => {
+                    ast::ItemStatic(_, _, init) => {
                         if attr::contains_name(item.attrs.as_slice(),
                                                "address_insignificant") {
                             self.reachable_symbols.remove(&search_item);
                         }
+                        visit::walk_expr(self, init, ());
                     }
 
                     // These are normal, nothing reachable about these

src/test/auxiliary/issue-13620-1.rs

+// Copyright 2012-2014 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.
+
+pub struct Foo {
+    pub foo: extern fn()
+}
+
+extern fn the_foo() {}
+
+pub static FOO: Foo = Foo {
+    foo: the_foo
+};

src/test/auxiliary/issue-13620-2.rs

+// Copyright 2012-2014 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.
+
+extern crate crate1 = "issue-13620-1";
+
+pub static FOO2: crate1::Foo = crate1::FOO;

src/test/run-pass/issue-13620.rs

+// Copyright 2012-2014 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-13620-1.rs
+// aux-build:issue-13620-2.rs
+
+extern crate crate2 = "issue-13620-2";
+
+fn main() {
+    (crate2::FOO2.foo)();
+}