[clang-tools-extra] [clang-tidy] In C++17, callee is guaranteed to be sequenced before arguments. (PR #93623)

[Kefu Chai via cfe-commits]

================
@@ -175,6 +218,10 @@ bool UseAfterMoveFinder::findInternal(const CFGBlock *Block,
             MovingCall != nullptr &&
             Sequence->potentiallyAfter(MovingCall, Use);
 
+        // We default to false here and change this to true if required in
+        // find().
+        TheUseAfterMove->UseHappensInLaterLoopIteration = false;
+
----------------
tchaikov wrote:

agreed. but practically, we reference `EvaluationOrderUndefined` only if `UseAfterMoveFinder::find()` returns `true`, which indicates a use-after-move is identified. see https://github.com/llvm/llvm-project/blob/4d95850d052336a785651030eafa0b24651801a0/clang-tools-extra/clang-tidy/bugprone/UseAfterMoveCheck.cpp#L498-L501, and the only two places where we return `true` in `UseAfterMoveFinder::findInternal()` are

1. https://github.com/llvm/llvm-project/blob/4d95850d052336a785651030eafa0b24651801a0/clang-tools-extra/clang-tidy/bugprone/UseAfterMoveCheck.cpp#L178
2. https://github.com/llvm/llvm-project/blob/4d95850d052336a785651030eafa0b24651801a0/clang-tools-extra/clang-tidy/bugprone/UseAfterMoveCheck.cpp#L188

the 2nd case is a recursive call to `UseAfterMoveFinder::findInternal()`. and the 1st case is where we set `UseHappensInLaterLoopIteration` to `false`. and we may set this member variable to `true` later on.

probably a more readable implementation is to return an `optional<UseAfterMove>` from `UseAfterMoveFinder::find()`, so that it's obvious that `UseAfterMove` is always initialized and returned if we find a use-after-move. but that'd be a cleanup, and not directly related to this PR. if it acceptable to piggy back it into this PR, i will do it.

https://github.com/llvm/llvm-project/pull/93623