[PATCH] D62845: [clang-tidy] Fix make-unique tests on C++2a.

[Haojian Wu via Phabricator via cfe-commits]

hokein added a comment.

In D62845#1528791 <https://reviews.llvm.org/D62845#1528791>, @gribozavr wrote:

> I'd suggest to add a separate file that covers the exact language modes needed.
>
> The C++14 test that we have right now is about C++14-or-later, testing the availability of std::make_unique.


The test file name ("modernize-make-unique-cxx14") indicates this test is for C++14, and since we change the existing `modernize-make-unique` test (which covers more cases) to C++14 or later, I think it is reasonable to restrict the `cxx14` test to run only on C++14. or am I missing anything?

> I'm also not sure what the intent behind these tests is. Maybe the right fix is to add a constructor that can be called?

sorry, the check is too complicated to catch up, the test cases are testing the code path https://github.com/llvm/llvm-project/blob/master/clang-tools-extra/clang-tidy/modernize/MakeSmartPtrCheck.cpp#L405.

Unfortunately, adding a default constructor doesn't fix the problem: the AST tree is different in C++14/17 and C++2a, which causes different behavior in the check.

e.g. `new NoCopyMoveCtor{}`

In C++14/17, it looks like below, the check thinks it is an aggregate initialization (with deleted copy/move constructor) and doesn't generate the fix.

  |-CXXNewExpr <line:26:3, col:22> 'NoCopyMoveCtor *' Function 0x5614cfece8f0 'operator new' 'void *(std::size_t)'
      | `-InitListExpr <col:21, col:22> 'NoCopyMoveCtor'

However, in C++2a, the AST is like below, the check thinks it is a direct initialization with default constructor, and generate the fix.

  `-CXXNewExpr <line:26:3, col:22> 'NoCopyMoveCtor *' Function 0x55c9b1b24ba0 'operator new' 'void *(std::size_t)'
        `-CXXConstructExpr <col:7, col:22> 'NoCopyMoveCtor' 'void () noexcept' list zeroing




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