[clang] [clang-tools-extra] [Clang] Make the SizeType, SignedSizeType and PtrdiffType be named sugar types instead of built-in types (PR #143653)

[Matheus Izvekov via cfe-commits]

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@@ -5216,6 +5237,25 @@ QualType ASTContext::getDependentBitIntType(bool IsUnsigned,
   return QualType(New, 0);
 }
 
+QualType ASTContext::getPredefinedSugarType(uint32_t KD) const {
+  using Kind = PredefinedSugarType::Kind;
+  auto getUnderlyingType = [](const ASTContext &Ctx, Kind KDI) -> QualType {
+    switch (KDI) {
+    case Kind::SizeT:
+      return Ctx.getFromTargetType(Ctx.Target->getSizeType());
+    case Kind::SignedSizeT:
+      return Ctx.getFromTargetType(Ctx.Target->getSignedSizeType());
+    case Kind::PtrdiffT:
+      return Ctx.getFromTargetType(Ctx.Target->getPtrDiffType(LangAS::Default));
+    }
+    llvm_unreachable("unexpected kind");
+  };
+  auto *New = new (*this, alignof(PredefinedSugarType)) PredefinedSugarType(
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mizvekov wrote:

I'd have a preference to unique the types here, instead of relying on us only calling this once and storing these on ad-hoc named members of ASTContext, just because its harder to make mistakes.

https://github.com/llvm/llvm-project/pull/143653