[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]

================
@@ -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(
+      static_cast<Kind>(KD), getUnderlyingType(*this, static_cast<Kind>(KD)));
----------------
mizvekov wrote:

These should already be canonical types, right?
```suggestion
  auto getCanonicalType = [](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(
      static_cast<Kind>(KD), getCanonicalType(*this, static_cast<Kind>(KD)));
```

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