Intermittent travis macOS test failures in leantest_non_meta_rec_fn.lean

[bryangingechen]

Sometimes the macOS clang++ travis build fails during the ctest step in leantest_non_meta_rec_fn.lean like this:

379/1325 Test #283: leantest_non_meta_rec_fn.lean ...............................***Failed    0.05 sec

-- testing non_meta_rec_fn.lean

-- using result from test_all.sh

--- non_meta_rec_fn.lean.expected.out	2019-10-17 20:25:29.000000000 +0000

+++ non_meta_rec_fn.lean.produced.out	2019-10-17 20:34:55.000000000 +0000

@@ -1,4 +1,4 @@

-non_meta_rec_fn.lean:3:36: error: failed to prove recursive application is decreasing, well founded relation

+non_meta_rec_fn.lean:3:0: error: failed to prove recursive application is decreasing, well founded relation

   @has_well_founded.r true (@has_well_founded_of_has_sizeof true (default_has_sizeof true))

 Possible solutions: 

   - Use 'using_well_founded' keyword in the end of your definition to specify tactics for synthesizing well founded relations and decreasing proofs.

ERROR: file non_meta_rec_fn.lean.produced.out does not match non_meta_rec_fn.lean.expected.out

It seems to happen randomly; I think I've seen it go away after the job was restarted.

cf. #69 (comment)

Here are a bunch of other instances I found in the travis "build history" tab which go back several months:

• https://travis-ci.org/leanprover-community/lean/jobs/599329732#L1895
• https://travis-ci.org/leanprover-community/lean/jobs/559029182#L4601
• https://travis-ci.org/leanprover-community/lean/jobs/594302054#L4955
• https://travis-ci.org/leanprover-community/lean/jobs/543879667#L4469
• https://travis-ci.org/leanprover-community/lean/jobs/542915441#L4462
• https://travis-ci.org/leanprover-community/lean/jobs/538388974#L4422

[bryangingechen]

This should be fixed by #104.