extra::fileinput tests are periodically failing

[huonw]

Some tests in extra::fileinput are occasionally failing on unrelated PRs (that one is from #9051 on mac, and there was a failure on #9054 on windows)

Relevant part of the first one (in case the file disappears):

task <unnamed> failed at 'called `Result::unwrap()` on `Err` value: error opening tmp/lib-fileinput-test-input-vec-2.tmp', /Users/rustbuild/src/rust-buildbot/slave/auto-mac-32-opt/build/src/libstd/result.rs:120
task <unnamed> failed at 'called `Result::unwrap()` on `Err` value: error opening tmp/lib-fileinput-test-input-vec-state-1.tmp', /Users/rustbuild/src/rust-buildbot/slave/auto-mac-32-opt/build/src/libstd/result.rs:120
test fileinput::test::test_fileinput_read_byte ... ok
test json::tests::test_decode_enum ... ok
task <unnamed> failed at 'called `Result::unwrap()` on `Err` value: error opening tmp/lib-fileinput-test-next-file-1.tmp', /Users/rustbuild/src/rust-buildbot/slave/auto-mac-32-opt/build/src/libstd/result.rs:120
test hex::tests::test_to_hex_all_bytes ... ok
test hex::tests::test_from_hex_all_bytes ... ok
test json::tests::test_decode_identifiers ... ok
test json::tests::test_decode_list ... ok
test json::tests::test_decode_map ... ok
test json::tests::test_decode_numbers ... ok
test json::tests::test_decode_option ... ok
test json::tests::test_decode_str ... ok
test fileinput::test::test_input_vec ... FAILED
test fileinput::test::test_next_file ... FAILED
test json::tests::test_multiline_errors ... ok
test json::tests::test_decode_struct ... ok
test json::tests::test_read_identifiers ... ok
test json::tests::test_read_list ... ok
test json::tests::test_read_number ... ok
test fileinput::test::test_input_vec_state ... FAILED

And the failure message on windows (only test_next_file failed there):

task <unnamed> failed at 'called `Result::unwrap()` on `Err` value: error opening tmp\lib-fileinput-test-next-file-0.tmp', C:\bot\slave\auto-win-32-nopt-t\build\src\libstd\result.rs:120

[alexcrichton]

I tried to reproduce this by running the tests a few hundred times back-to-back, but to no avail (OSX x86_64)

[alexcrichton]

I believe that this was fixed when tests stopped using change_dir_locked