method on non-generic priv struct callable via re-exported type alias leads to link failure

[pnkfelix]

While narrowing down to a small test case for #14421 , I encountered the following issue:

A library might want to have a single private struct that is only exposed via a named type for that struct (*).

But it seems like this causes a link failure for clients of that library. (Probably because some dead-code elimination pass is relying on accurate results from the reachability analysis, which is breaking in this scenario as described in #14421.)

(I keep wondering if I'm missing some obvious explanation for this in my code, but I have reviewed the test a couple times and cannot find a reason to explain this except a hypothetical rustc bug.)

bug_lib.rs

#![crate_type="lib"]

pub use src::aliases::B;
pub use src::hidden_core::make;

mod src {
    pub mod aliases {
        use super::hidden_core::A;
        pub type B = A;
    }

    pub mod hidden_core {
        use super::aliases::B;

        pub struct A;

        pub fn make() -> B { A }

        impl A {
            pub fn foo(&mut self) { println!("called foo"); }
        }
    }
}

bug_client.rs

extern crate bug_lib;

use bug_lib::B;
use bug_lib::make;

fn main() {
    let mut an_A : B  = make();
    an_A.foo();
}

transcript

% ./x86_64-apple-darwin/stage2/bin/rustc --version
rustc 0.11.0-pre (e402e75 2014-05-22 13:31:24 -0700)
host: x86_64-apple-darwin
% ./x86_64-apple-darwin/stage2/bin/rustc --out-dir /tmp /tmp/bug_lib.rs
/tmp/bug_lib.rs:20:13: 20:62 warning: code is never used: `foo`, #[warn(dead_code)] on by default
/tmp/bug_lib.rs:20             pub fn foo(&mut self) { println!("called foo"); }
                               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
%  ./x86_64-apple-darwin/stage2/bin/rustc -L /tmp/ /tmp/bug_client.rs
error: linking with `cc` failed: exit code: 1
note: cc '-m64' '-L' '/Users/pnkfelix/Dev/Mozilla/rust.git/objdir-dbgopt/x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-darwin/lib' '-o' 'bug_client' 'bug_client.o' '-lmorestack' '-nodefaultlibs' '-Wl,-dead_strip' '/Users/pnkfelix/Dev/Mozilla/rust.git/objdir-dbgopt/x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-darwin/lib/libnative-1fb5e2c0-0.11.0-pre.rlib' '/private/tmp/libbug_lib-ef5c9cd9-0.0.rlib' '/Users/pnkfelix/Dev/Mozilla/rust.git/objdir-dbgopt/x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-darwin/lib/libstd-59beb4f7-0.11.0-pre.rlib' '/Users/pnkfelix/Dev/Mozilla/rust.git/objdir-dbgopt/x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-darwin/lib/liballoc-1085c790-0.11.0-pre.rlib' '/Users/pnkfelix/Dev/Mozilla/rust.git/objdir-dbgopt/x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-darwin/lib/libcore-c5ed6fb4-0.11.0-pre.rlib' '/Users/pnkfelix/Dev/Mozilla/rust.git/objdir-dbgopt/x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-darwin/lib/liblibc-4f9a876d-0.11.0-pre.rlib' '-L' '/tmp' '-L' '/Users/pnkfelix/Dev/Mozilla/rust.git/objdir-dbgopt/.rust' '-L' '/Users/pnkfelix/Dev/Mozilla/rust.git/objdir-dbgopt' '-lSystem' '-lpthread' '-lc' '-lm' '-Wl,-rpath,@loader_path/x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-darwin/lib' '-Wl,-rpath,/Users/pnkfelix/opt/rust-dbg/lib/rustlib/x86_64-apple-darwin/lib' '-lcompiler-rt'
note: ld: warning: directory not found for option '-L/Users/pnkfelix/Dev/Mozilla/rust.git/objdir-dbgopt/.rust'
Undefined symbols for architecture x86_64:
  "src::hidden_core::A::foo::h874f4919cda4bfc2Aaa::v0.0", referenced from:
      main::hea3b2ec4fbc3f438haa::v0.0 in bug_client.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

error: aborting due to previous error
% 

(*) Who knows why, perhaps the library designer doesn't like the names chosen by a fellow developer, but does not want to go through the effort of alpha-renaming. In any case, if #14421 works then this case seems like it should work as well.