Linker error when importing a some rlib's symbols through a dylib

[UberLambda]

Suppose having a project setup similiar to this one (replace _ in filenames with path separators).

The following conditions are met:

• A static library, that I'll call A, has a public module in it
• There's a dynamic library named B that has A as a Cargo dependency
• B links to A with a extern crate A; statement, and exports some of A's modules with pub use A::module; in B's lib.rs
• A binary/other library named C links to B and tries to use one of B's modules that are just a reexport of A modules

The linking of C with the default linker, fails with the following output:

error: linking with `cc` failed: exit code: 1
note: cc '-m64' '-L' '/usr/lib64/rustlib/x86_64-unknown-linux-gnu/lib' '-o' '/home/paolo/rust-bugs/C/target/C' '/home/paolo/rust-bugs/C/target/C.o' '-Wl,--whole-archive' '-lmorestack' '-Wl,--no-whole-archive'
'-nodefaultlibs' '-fno-lto' '-Wl,--gc-sections' '-pie' '-Wl,--as-needed' '-L' '/home/paolo/rust-bugs/C/target/deps' '-lB-7ff4c82ee0366c0f' '-L' '/usr/lib/rustlib/x86_64-unknown-linux-gnu/lib' '-lnative-4e7c5e5c' '-L' '/usr/lib/rustlib/x86_64-unknown-linux-gnu/lib'
'-lstd-4e7c5e5c' '-L' '/usr/lib/rustlib/x86_64-unknown-linux-gnu/lib' '-lsync-4e7c5e5c' '-L' '/usr/lib/rustlib/x86_64-unknown-linux-gnu/lib' '-lrustrt-4e7c5e5c' '-L' '/home/paolo/rust-bugs/C/target' '-L' '/home/paolo/rust-bugs/C/target/deps'
'-L' '/home/paolo/rust-bugs/C/.rust' '-L' '/home/paolo/rust-bugs/C' '-Wl,--whole-archive' '-Wl,-Bstatic' '-Wl,--no-whole-archive' '-Wl,-Bdynamic' '-ldl' '-lpthread' '-lgcc_s' '-lpthread' '-lc' '-lm' '-lcompiler-rt'
note: /home/paolo/rust-bugs/C/target/C.o: in function "C::main":
/home/paolo/rust-bugs/C/src/main.rs:6: undefined reference to "amod::Test::new::hbd984620e5bd9235oaa"
collect2: error: ld returned 1 exit status

error: aborting due to previous error
Could not compile `C`.

If C links directly to A, whilst still linking to B, and tries to use A::amod instead of B::amod, the problem persists. Discarding B completely (e.g. without extern crate B in C's root) fixes it.

[alexcrichton]

This is a dupe of #14344, but thanks for the test case!

[UberLambda]

:)