[clang] fba88ad - [Sema] Always perform ADL when searching for transormed operators in C++20

[Ilya Biryukov via cfe-commits]

Author: Ilya Biryukov
Date: 2022-08-12T16:07:02+02:00
New Revision: fba88adc8961fc8b8d7dece7bfecbfc31c652aff

URL: https://github.com/llvm/llvm-project/commit/fba88adc8961fc8b8d7dece7bfecbfc31c652aff
DIFF: https://github.com/llvm/llvm-project/commit/fba88adc8961fc8b8d7dece7bfecbfc31c652aff.diff

LOG: [Sema] Always perform ADL when searching for transormed operators in C++20

This fixes compilation errors in the following code with
latest libc++ and libstdc++:
```cpp

int main() {
  std::tuple<std::string> s;
  std::tuple<std::string_view> sv;
  s < sv;
}
```

See https://gcc.godbolt.org/z/vGvEhxWvh for the error.

This used to happen because repeated template instantiations during
C++20 constraint satisfaction will cause a call to `RebuildCXXRewrittenBinaryOperator`
with `PerformADL` set to false, see https://github.com/llvm/llvm-project/blob/59351fe340f20a605bae53260ed30a8e0fd95cb6/clang/lib/Sema/TreeTransform.h#L2737

Committing urgently to unbreak breakages we see in our configurations.
The change seems relatively safe and the right thing to do.

However, I will follow-up with tests and investigation on whether we
need to do this extra semantic checking in the first place next week.

Added: 
    

Modified: 
    clang/lib/Sema/SemaOverload.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index c88413b3e5de..91e308d0d0fe 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -13930,7 +13930,7 @@ ExprResult Sema::CreateOverloadedBinOp(SourceLocation OpLoc,
 
             R = CreateOverloadedBinOp(
                 OpLoc, Opc, Fns, IsReversed ? ZeroLiteral : R.get(),
-                IsReversed ? R.get() : ZeroLiteral, PerformADL,
+                IsReversed ? R.get() : ZeroLiteral, /*PerformADL=*/true,
                 /*AllowRewrittenCandidates=*/false);
 
             popCodeSynthesisContext();