[clang] [clang] Fix elaborated keyword canonicalization (PR #135916)

[Erich Keane via cfe-commits]

================
@@ -1938,6 +1938,17 @@ TagDecl *Type::getAsTagDecl() const {
   return nullptr;
 }
 
+const TemplateSpecializationType *
+Type::getAsNonAliasTemplateSpecializationType() const {
+  for (const auto *T = this; /**/; /**/) {
+    const TemplateSpecializationType *TST =
+        T->getAs<TemplateSpecializationType>();
+    if (!TST || !TST->isTypeAlias())
+      return TST;
+    T = TST->desugar().getTypePtr();
+  }
+}
----------------
erichkeane wrote:

Ah, right, so:

```
const auto *TST = this->getAs<TemplateSpecializationType>();

while (TST && TST->isTypeAlias()) {
  TST = TST->desugar()->getAs<TemplateSpecializationType>();
}
return TST;
```
Right?  I think that does what you were intending.  Effectively a 'while is-type-specialization-type and is-type-alias'.

https://github.com/llvm/llvm-project/pull/135916