[PATCH] D137205: [clang-tidy] Add performance-unnecessary-copy-on-last-use check

[Fabian Keßler via Phabricator via cfe-commits]

Febbe added a comment.

In D137205#3912243 <https://reviews.llvm.org/D137205#3912243>, @Skylion007 wrote:

> One other bug I found with this diff, is it seems to suggest calling std::move() on function args that are references, despite the fact that invalidating the reference to the input arg could be undesirable. For instance take a function that takes in a reference to a String, assigns a new value to the arg reference, and then returns the value of the reference. It suggests calling std::move() on the arg ref when it is returned, which invalidate the reference to the argument.

Oh, that's not good. Actually, it should not run on references, only  `declRefExpr(hasType(qualType(unless(anyOf(

  isConstQualified(), referenceType(), pointerType() ,..)` are allowed to be parsed.

Did you run this check alone, without other checks?

Regarding the appearance of `std::move(std::move( var );`, was there a move already? Does it occur in a header file? In case of running clang-tidy with fixups in parallel over multiple sources, it can happen, that a header file is parsed twice at the same time, resulting in duplicate insertions.

And last but not least, can you provide a source snipped or AST for both appearances?


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  https://reviews.llvm.org/D137205/new/

https://reviews.llvm.org/D137205