[clang] [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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@@ -5148,6 +5153,14 @@ QualType ASTContext::getDependentBitIntType(bool IsUnsigned,
   return QualType(New, 0);
 }
 
+QualType ASTContext::getPredefinedSugarType(uint32_t KD,
+                                            QualType UnderlyingType) const {
+  auto *New = new (*this, alignof(PredefinedSugarType)) PredefinedSugarType(
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mizvekov wrote:

This should be uniqued like the other types.
If you drop the UnderlyingType, then this is really simple, as there are only three kinds and you can use a small array instead of a folding set node.

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