[clang] Turn 'counted_by' into a type attribute and parse it into 'CountAttributedType' (PR #78000)

[Aaron Ballman via cfe-commits]

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@@ -7239,6 +7239,13 @@ QualType TreeTransform<Derived>::TransformAttributedType(TypeLocBuilder &TLB,
       });
 }
 
+template <typename Derived>
+QualType TreeTransform<Derived>::TransformCountAttributedType(
+    TypeLocBuilder &TLB, CountAttributedTypeLoc TL) {
+  // TODO
+  llvm_unreachable("Unexpected TreeTransform for CountAttributedType");
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AaronBallman wrote:

Hmmm this might be problematic sooner rather than later; the attribute is only allowed in C mode so we don't have to worry about needing this for template instantiation, but we do use `TreeTransform` in C for OpenMP: https://github.com/llvm/llvm-project/blob/d2a9df2c8ffd21fd52fbd8199a191d10078f41af/clang/lib/Sema/SemaOpenMP.cpp#L5591

https://github.com/llvm/llvm-project/pull/78000