[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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@@ -2258,6 +2258,27 @@ class alignas(TypeAlignment) Type : public ExtQualsTypeCommonBase {
     unsigned NumExpansions;
   };
 
+  enum class PredefinedSugarKind {
+    /// The "size_t" type.
+    SizeT,
+
+    /// The "signed size_t" type.
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mizvekov wrote:

Well that's another good reason, but I was more worried about the inconsistency, and the fact that this is not even a valid type spelling: 'signed' is a specifier, not a qualifier, and it can't be attached to a typedef name.

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