Internal error: Could not find class when running hh_client --lint --json

[Atry]

I am creating a test triggering hh_client --lint --json against some temporary files.

The content of the temporary source file is like

/*
 *  Copyright (c) 2017-present, Facebook, Inc.
 *  All rights reserved.
 *
 *  This source code is licensed under the MIT license found in the
 *  LICENSE file in the root directory of this source tree.
 *
 */
final class Test {
  private static function testThis() {
    \SomeNamespace\__Private\SomeEnumName::SOME_VALUE;
  }
}

Even though this file should not type check, I would expect no lint errors should be reported.

However, when hh_client --lint path/to/the/temporary/file.hack --json is running, sometimes hh_client prints the following error:

{"descr":"Internal error: Could not find class","severity":"error","path":"\/workspaces\/hhast\/.var\/tmp\/hhast\/HHClientDuplicatedLintErrorTest\/1902a47e82576d16a1e026e177dc583b.php","line":9,"start":13,"end":16,"code":0,"bypass_changed_lines":false,"original":"","replacement":""}

To trigger this bug:

git clone https://github.com/atry/hhast.git --branch hhvm-bug-report && cd hhast && composer install && vendor/bin/hacktest tests/HHClientDuplicatedLintErrorTest.hack

This bug is not reproducible from manual execution of hh_client --lint --json, because it only happens when the temporary file is newly created (maybe while the typechecking is still running?) and there are many concurrent hh_client calls (some race condition?).