heisenbug

[John-Colvin]

This happened on one travis run. It's passed before, looks like a heisenbug.

LDC - the LLVM D compiler (1.0.0):
  based on DMD v2.070.2 and LLVM 3.8.0
  built with LDC - the LLVM D compiler (1.0.0)
  Default target: x86_64-unknown-linux-gnu
  Host CPU: ivybridge
  http://dlang.org - http://wiki.dlang.org/LDC
  Registered Targets:
    x86    - 32-bit X86: Pentium-Pro and above
    x86-64 - 64-bit X86: EM64T and AMD64
$ dub --help | tail -n 1
DUB version 1.1.1, built on Dec  2 2016
4.24s$ dub test --compiler=$DC
Generating test runner configuration '__test__lib__' for 'lib' (library).
Performing "unittest" build using ldc2 for x86_64.
parallel-algorithms ~master: building configuration "__test__lib__"...
Running ./__test__lib__ 
core.exception.AssertError@source/parallel_algorithm.d(815): Assertion failure