Linking error unless 'use'd

[TheNeikos]

While working on a sample game with rust I encountered a strange bug which I believe to be a corner case of the setup I have. I am unable to recreate it in a simpler crate, so I am going to submit the code as I have it right now, hoping someone else might spot what is going wrong.

I have created a branch on my project that should reproduce this bug: https://github.com/TheNeikos/rpg/tree/error-linker

If you comment in line 13 in lib.rs it will compile.

Output of cargo run in that project:

neikos@celestias-palace ~/p/r/rpg> cargo run
   Compiling server v0.1.0 (file:///home/neikos/projects/rust/rpg)
<<<< Lots of warnings about unused stuff >>>>
error: linking with `cc` failed: exit code: 1
note: "cc" "-Wl,--as-needed" "-m64" "-L" "/usr/lib64/rustlib/x86_64-unknown-linux-gnu/lib" "/home/neikos/projects/rust/rpg/target/debug/rpg.o" "-o" "/home/neikos/projects/rust/rpg/target/debug/rpg" "-Wl,--whole-archive" "-l" "morestack" "-Wl,--no-whole-archive" "-Wl,--gc-sections" "-pie" "-nodefaultlibs" "/home/neikos/projects/rust/rpg/target/debug/deps/libserver-503340237efbae24.rlib" "/home/neikos/projects/rust/rpg/target/debug/deps/libshared-9e1f1e1585409fc5.rlib" "/home/neikos/projects/rust/rpg/target/debug/deps/libclock_ticks-995f487ba7426efb.rlib" "/home/neikos/projects/rust/rpg/target/debug/deps/liblibc-ef5cbad4ef5c7a1e.rlib" "/home/neikos/projects/rust/rpg/target/debug/deps/libbincode-1533ee1770371aad.rlib" "/home/neikos/projects/rust/rpg/target/debug/deps/librustc_serialize-c1e8163a38ed3d54.rlib" "/home/neikos/projects/rust/rpg/target/debug/deps/libbyteorder-399c175f6a7726ac.rlib" "/usr/lib/rustlib/x86_64-unknown-linux-gnu/lib/libstd-74fa456f.rlib" "/usr/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcollections-74fa456f.rlib" "/usr/lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_unicode-74fa456f.rlib" "/usr/lib/rustlib/x86_64-unknown-linux-gnu/lib/librand-74fa456f.rlib" "/usr/lib/rustlib/x86_64-unknown-linux-gnu/lib/liballoc-74fa456f.rlib" "/usr/lib/rustlib/x86_64-unknown-linux-gnu/lib/liblibc-74fa456f.rlib" "/usr/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcore-74fa456f.rlib" "-L" "/home/neikos/projects/rust/rpg/target/debug" "-L" "/home/neikos/projects/rust/rpg/target/debug/deps" "-L" "/usr/lib64/rustlib/x86_64-unknown-linux-gnu/lib" "-L" "/home/neikos/projects/rust/rpg/.rust/lib64/x86_64-unknown-linux-gnu" "-L" "/home/neikos/projects/rust/rpg/lib64/x86_64-unknown-linux-gnu" "-Wl,-Bstatic" "-Wl,-Bdynamic" "-l" "rt" "-l" "c" "-l" "m" "-l" "dl" "-l" "pthread" "-l" "rt" "-l" "gcc_s" "-l" "pthread" "-l" "c" "-l" "m" "-l" "compiler-rt"
note: /home/neikos/projects/rust/rpg/target/debug/rpg.o: In function `rpg::main':
/home/neikos/projects/rust/rpg/src/main.rs:42: undefined reference to `player::Player::get_id::hf61907f5ded04b74cfa'
collect2: error: ld returned 1 exit status

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

To learn more, run the command again with --verbose.
neikos@celestias-palace ~/p/r/rpg> cargo -V
cargo 0.4.0-nightly (90422d6 2015-07-07) (built 2015-07-06)
neikos@celestias-palace ~/p/r/rpg> 

I think I am right to assume that rustc should error rather than the linker, as I found out the fix for this by random chance.

[alexcrichton]

I believe that this is a dupe of #16734, so closing in favor of that.