[PATCH] D71918: fix river's comment and add the test

[pre-merge checks [bot] via Phabricator via llvm-commits]

merge_guards_bot added a comment.

{icon question-circle color=gray} Unit tests: unknown.

{icon question-circle color=gray} clang-tidy: unknown.

{icon question-circle color=gray} clang-format: unknown.

Build artifacts <http://results.llvm-merge-guard.org/amd64_debian_testing_clang8-664>: diff.json <http://results.llvm-merge-guard.org/amd64_debian_testing_clang8-664/diff.json>, console-log.txt <http://results.llvm-merge-guard.org/amd64_debian_testing_clang8-664/console-log.txt>


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D71918/new/

https://reviews.llvm.org/D71918