ICE: a type named ... has already been imported in this module.

[tbu-]

$ RUST_BACKTRACE=1 make
cfg: version 1.3.0-dev (fd8e175c4 2015-07-08)
cfg: build triple x86_64-unknown-linux-gnu
cfg: host triples x86_64-unknown-linux-gnu
cfg: target triples x86_64-unknown-linux-gnu
cfg: host for x86_64-unknown-linux-gnu is x86_64
cfg: os for x86_64-unknown-linux-gnu is unknown-linux-gnu
cfg: good valgrind for x86_64-unknown-linux-gnu is 1
cfg: using CC=gcc (CFG_CC)
cfg: enabling valgrind run-pass tests (CFG_ENABLE_VALGRIND_RPASS)
cfg: valgrind-rpass command set to "/usr/bin/valgrind" --error-exitcode=100 --fair-sched=try --quiet --soname-synonyms=somalloc=NONE --suppressions=<path>/rust/src/etc/x86.supp  --tool=memcheck --leak-check=full
cfg: no pandoc found, omitting PDF and EPUB docs
rustc: x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib/libstd
src/libstd/sys/unix/os.rs:24:5: 24:9 error: a type named `libc` has already been imported in this module [E0252]
src/libstd/sys/unix/os.rs:24 use libc;
                                 ^~~~
src/libstd/sys/unix/os.rs:24:5: 24:9 help: run `rustc --explain E0252` to see a detailed explanation
error: internal compiler error: unexpected panic
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
note: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'expected item, found unknown node (id=77573)', /home/rustbuild/src/rust-buildbot/slave/snap3-linux/build/src/libsyntax/ast_map/mod.rs:332

stack backtrace:
   1:     0x7f4ddcfa6889 - sys::backtrace::write::h8a79f17bd32af79cw6r
   2:     0x7f4ddcfaaf99 - panicking::on_panic::h006e51db1ed1fe0aHMw
   3:     0x7f4ddcf87e92 - rt::unwind::begin_unwind_inner::hc3f0d363d76c49d8Rrw
   4:     0x7f4ddcf88977 - rt::unwind::begin_unwind_fmt::hc35fd2b409178390Xqw
   5:     0x7f4ddcc9b164 - ast_map::Map<'ast>::expect_item::h5aa30640bac7278eFNw
   6:     0x7f4ddb75d00a - resolve_imports::ImportResolver<'a, 'b, 'tcx>::check_for_conflicting_import::h6ea3619a6cd9fe3bH4c
   7:     0x7f4ddb75c6ec - resolve_imports::ImportResolver<'a, 'b, 'tcx>::resolve_single_import::closure.15532
   8:     0x7f4ddb75922c - resolve_imports::ImportResolver<'a, 'b, 'tcx>::resolve_import_for_module::hadc6af6523c7b803ydc
   9:     0x7f4ddb755964 - resolve_imports::ImportResolver<'a, 'b, 'tcx>::resolve_imports_for_module_subtree::hd897beb4adc12cb3d6b
  10:     0x7f4ddb756122 - resolve_imports::ImportResolver<'a, 'b, 'tcx>::resolve_imports_for_module_subtree::hd897beb4adc12cb3d6b
  11:     0x7f4ddb756122 - resolve_imports::ImportResolver<'a, 'b, 'tcx>::resolve_imports_for_module_subtree::hd897beb4adc12cb3d6b
  12:     0x7f4ddb798efc - resolve_crate::h099d31118e996bc7Tai
  13:     0x7f4ddb4bae52 - driver::phase_3_run_analysis_passes::hb2cfd88f31771c50GGa
  14:     0x7f4ddb49fc8c - driver::compile_input::he676e67531d7acc5Qba
  15:     0x7f4ddb555e51 - run_compiler::h79d396569d40b0bao6b
  16:     0x7f4ddb5536a2 - boxed::F.FnBox<A>::call_box::h2275685322063474542
  17:     0x7f4ddb552e79 - rt::unwind::try::try_fn::h16543066540276063477
  18:     0x7f4ddcfb0378 - rust_try_inner
  19:     0x7f4ddcfb0365 - rust_try
  20:     0x7f4ddcf9e727 - rt::unwind::try::inner_try::hf64073dde2f58c9eKnw
  21:     0x7f4ddb5530aa - boxed::F.FnBox<A>::call_box::h222783876647075817
  22:     0x7f4ddcfa9dd1 - sys::thread::Thread::new::thread_start::ha4e6321e5d782d8c0xv
  23:     0x7f4ddaed6353 - start_thread
  24:     0x7f4dda2eebfc - __clone
  25:                0x0 - <unknown>

<path>/git/rust/mk/target.mk:171: recipe for target 'x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib/stamp.std' failed
make: *** [x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib/stamp.std] Error 101

Using the following diff:

$ git diff
diff --git a/src/libstd/sys/unix/os.rs b/src/libstd/sys/unix/os.rs
index 334dd6b..b60faf6 100644
--- a/src/libstd/sys/unix/os.rs
+++ b/src/libstd/sys/unix/os.rs
@@ -21,6 +21,7 @@ use fmt;
 use io;
 use iter;
 use libc::{self, c_int, c_char, c_void};
+use libc;
 use mem;
 use ptr;
 use path::{self, PathBuf};

[euclio]

Got this today. Can reproduce with something as simple as

use std::sync::{Arc};
use std::sync::Arc;

[arielb1]

does not affect 1.3+

[tbu-]

Can confirm, no longer a problem. Should I close this issue?

[alexcrichton]

It'd probably good to check in a test just to make sure, and now that this has E-needstest it'll just make its way into src/test at some point

[Manishearth]

Opened #29273