[clang] [Clang] add user-level sizeless attribute (PR #71894)

[Timm Baeder via cfe-commits]

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@@ -2400,7 +2402,66 @@ bool Type::isWebAssemblyTableType() const {
   return false;
 }
 
-bool Type::isSizelessType() const { return isSizelessBuiltinType(); }
+bool Type::isSizelessType() const {
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tbaederr wrote:

The name of this function sounds like this is a simple getter, but it's quite expensive. Are the other `Type::is*Type()` functions similarly complex or can we rename this?

https://github.com/llvm/llvm-project/pull/71894