[libcxx-commits] [PATCH] D62719: A hot fix for exclusive_scan

[Marshall Clow via Phabricator via libcxx-commits]

mclow.lists added a comment.

In D62719#1527089 <https://reviews.llvm.org/D62719#1527089>, @MikeDvorskiy wrote:

> In D62719#1525450 <https://reviews.llvm.org/D62719#1525450>, @rodgert wrote:
>
> > Actually, we should probably get a test of some sort here before accepting the change. Yes, it's fairly obviously wrong and the fix is fairly obviously correct, but it's a regression and we should provide tests for regressions, lest certain standard library maintainers ask uncomfortable questions.
>
>
> Do you mean a test should we added which will coverage the fixed error? In other words we need a test which checks following thing:
>
> "Parallel algorithms shall not participate in overload resolution unless is_execution_policy_v<decay_-
>  t<ExecutionPolicy>> is true."
>
> Right?


Right.

> As far as I understand we should one call pear each algorithm with "fake" policy for  is_execution_policy_v<fake_policy> is false and get a compilation error like "exclusive_scan(....).... is not found".
>  Otherwise, test "fail". So, it is "negative" test, right?
>  So, I have two questions:
> 
> 1. Does LLVM test system support a negative test?

Yes it does. See (for example) "test/std/iterators/iterator.container/empty.array.fail.cpp"

> 2. If yes, to cover the all cases (to be sure that "enable_if is present") we have to add more 80 negative test units.

Agreed.


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