[clang] [Clang][WIP][RFC] Bypass TAD during overload resolution if a perfect match exists (PR #133426)

[Younan Zhang via cfe-commits]

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@@ -10918,7 +11083,44 @@ bool OverloadCandidate::NotValidBecauseConstraintExprHasError() const {
 OverloadingResult
 OverloadCandidateSet::BestViableFunction(Sema &S, SourceLocation Loc,
                                          iterator &Best) {
+
+  bool TwoPhaseResolution =
+      !NonDeducedCandidates.empty() && Kind != CSK_CodeCompletion &&
+      Kind != CSK_InitByUserDefinedConversion && Kind != CSK_InitByConstructor;
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zyn0217 wrote:

I must be missing something, are `CSK_InitByUserDefinedConversion` and `CSK_InitByConstructor` something special that we can't apply to them?

(explanations are appreciated!)

https://github.com/llvm/llvm-project/pull/133426