Running compile-fail tests after changing code results in "found crate std compiled by an incompatible version of rustc"

[shepmaster]

I was trying to follow a TDD-like process:

1. python ../x.py test ../src/test/compile-fail/ - note that only my test is failing, as expected
2. Make changes to src/librustc_typeck/check/mod.rs to address the failure
3. python ../x.py test ../src/test/compile-fail/ - all tests fail

The error from one of the tests:

------------------------------------------
error[E0514]: found crate `std` compiled by an incompatible version of rustc
  |
  = help: please recompile that crate using this compiler (rustc 1.17.0-dev (bf431b0f5 2017-02-10))
  = note: crate `std` path #1: /Users/shep/Projects/rust/build-release/build/x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-darwin/lib/libstd_unicode-5f2b70390d6f06f4.rlib compiled by "rustc 1.17.0-dev (435bb1c45 2017-02-10)"
  = note: crate `std` path #2: /Users/shep/Projects/rust/build-release/build/x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-darwin/lib/libstd_shim-6945dd0664fb6a35.rlib compiled by "rustc 1.17.0-dev (435bb1c45 2017-02-10)"
  = note: crate `std` path #3: /Users/shep/Projects/rust/build-release/build/x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-darwin/lib/libstd-6ce95fc10b65dc43.rlib compiled by "rustc 1.17.0-dev (435bb1c45 2017-02-10)"
  = note: crate `std` path #4: /Users/shep/Projects/rust/build-release/build/x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-darwin/lib/libstd-6ce95fc10b65dc43.dylib compiled by "rustc 1.17.0-dev (435bb1c45 2017-02-10)"

error: aborting due to previous error

The build script says that the build is complete:

$ python ../x.py build
    Finished debug [unoptimized] target(s) in 0.0 secs
Synchronizing submodule url for 'src/compiler-rt'
Synchronizing submodule url for 'src/jemalloc'
Synchronizing submodule url for 'src/liblibc'
Synchronizing submodule url for 'src/llvm'
Synchronizing submodule url for 'src/rt/hoedown'
Synchronizing submodule url for 'src/rust-installer'
HEAD is now at d30da544 Merge pull request #30 from japaric/msan
HEAD is now at 11bfb0d Merge pull request #16 from glandium/rust
HEAD is now at 8d8264b96 Auto merge of #512 - dumbbell:support-aarch64-unknown-freebsd, r=alexcrichton
HEAD is now at ceb177eeefa Merge pull request #60 from japaric/gh38406
HEAD is now at da282f1 Merge pull request #8 from GuillaumeGomez/line_information
HEAD is now at 4f99485 Merge pull request #54 from brson/docdir
Building stage0 std artifacts (x86_64-apple-darwin -> x86_64-apple-darwin)
    Finished release [optimized] target(s) in 0.0 secs
Copying stage0 std from stage0 (x86_64-apple-darwin -> x86_64-apple-darwin / x86_64-apple-darwin)
Building stage0 test artifacts (x86_64-apple-darwin -> x86_64-apple-darwin)
    Finished release [optimized] target(s) in 0.0 secs
Copying stage0 test from stage0 (x86_64-apple-darwin -> x86_64-apple-darwin / x86_64-apple-darwin)
Building stage0 compiler artifacts (x86_64-apple-darwin -> x86_64-apple-darwin)
    Finished release [optimized] target(s) in 0.0 secs
Copying stage0 rustc from stage0 (x86_64-apple-darwin -> x86_64-apple-darwin / x86_64-apple-darwin)
Copying stage1 compiler (x86_64-apple-darwin)
Building stage1 std artifacts (x86_64-apple-darwin -> x86_64-apple-darwin)
    Finished release [optimized] target(s) in 0.0 secs
Copying stage1 std from stage1 (x86_64-apple-darwin -> x86_64-apple-darwin / x86_64-apple-darwin)
Building stage1 test artifacts (x86_64-apple-darwin -> x86_64-apple-darwin)
    Finished release [optimized] target(s) in 0.0 secs
Copying stage1 test from stage1 (x86_64-apple-darwin -> x86_64-apple-darwin / x86_64-apple-darwin)
Building stage1 compiler artifacts (x86_64-apple-darwin -> x86_64-apple-darwin)
    Finished release [optimized] target(s) in 0.0 secs
Copying stage1 rustc from stage1 (x86_64-apple-darwin -> x86_64-apple-darwin / x86_64-apple-darwin)
Copying stage2 compiler (x86_64-apple-darwin)
Copying stage2 std from stage1 (x86_64-apple-darwin -> x86_64-apple-darwin / x86_64-apple-darwin)
Copying stage2 test from stage1 (x86_64-apple-darwin -> x86_64-apple-darwin / x86_64-apple-darwin)
Copying stage2 rustc from stage1 (x86_64-apple-darwin -> x86_64-apple-darwin / x86_64-apple-darwin)
Build completed in 0:00:03

This is using 2425b22.

[keeperofdakeys]

I've had the same issues a few times myself.

[alexcrichton]

I believe this is a dupe of #39396, so closing in favor of that.

[alexcrichton]

@shepmaster oh this may actually be a preexisting bug in the build system.

If you make a commit while you're working then the artifacts can get mixed up because the version has the git rev in it.

[shepmaster]

I forget if I made a commit or not. It's possible I might have, under the impression that changing the HEAD commit would force a rebuild of the appropriate tools.

[alexcrichton]

Yeah changing the head commit is something we don't check for right now but probably should! It looks like though that this is separate from #39396 so I'm gonna reopen.

[nikomatsakis]

Is there a workaround for this? I've just done ./x.py clean but ... that takes a while!

[alexcrichton]

@nikomatsakis

rm -rf build/*/stage0-tools

That should just recompile compiletest

[xiongmao86]

rm -rf build/*/stage0-std works for me.

[RalfJung]

touch src/librustc_metadata/lib.rs is another work-around suggested by @arielb1 that works well for me.

[Mark-Simulacrum]

This should be fixed by #43421, which will recompile the necessary crates based on their environment dependencies.