[demangler][NFC] Tweak legacy uuidof handling

We have to special-case 'u 8__uuidof [tz]' demangling for legacy
support.  That handling is a little duplicative.

* It seems better to just push the single expected node.

* We can also use 'consumeIf' rather than open-coding the peeking and increment.

* We don't need the numLeft < 2 check, as if there are few than that
  other paths will end up with detecting the error.

FWIW This simplifies a future change adding operator precedence.

Reviewed By: ChuanqiXu

Differential Revision: https://reviews.llvm.org/D119543

GitOrigin-RevId: 880e87580a219996f96ebf2cc9be9740f1a99a4c

src/demangle/ItaniumDemangle.h

diff --git a/src/demangle/ItaniumDemangle.h b/src/demangle/ItaniumDemangle.h
index 7d28f4d..a8d96fd 100644
--- a/src/demangle/ItaniumDemangle.h
+++ b/src/demangle/ItaniumDemangle.h
@@ -5032,30 +5032,29 @@
     // interpreted as <type> node 'short' or 'ellipsis'. However, neither
     // __uuidof(short) nor __uuidof(...) can actually appear, so there is no
     // actual conflict here.
+    bool IsUUID = false;
+    Node *UUID = nullptr;
     if (Name->getBaseName() == "__uuidof") {
-      if (numLeft() < 2)
-        return nullptr;
-      if (*First == 't') {
-        ++First;
-        Node *Ty = getDerived().parseType();
-        if (!Ty)
-          return nullptr;
-        return make<CallExpr>(Name, makeNodeArray(&Ty, &Ty + 1));
-      }
-      if (*First == 'z') {
-        ++First;
-        Node *Ex = getDerived().parseExpr();
-        if (!Ex)
-          return nullptr;
-        return make<CallExpr>(Name, makeNodeArray(&Ex, &Ex + 1));
+      if (consumeIf('t')) {
+        UUID = getDerived().parseType();
+        IsUUID = true;
+      } else if (consumeIf('z')) {
+        UUID = getDerived().parseExpr();
+        IsUUID = true;
       }
     }
     size_t ExprsBegin = Names.size();
-    while (!consumeIf('E')) {
-      Node *E = getDerived().parseTemplateArg();
-      if (E == nullptr)
-        return E;
-      Names.push_back(E);
+    if (IsUUID) {
+      if (UUID == nullptr)
+        return nullptr;
+      Names.push_back(UUID);
+    } else {
+      while (!consumeIf('E')) {
+        Node *E = getDerived().parseTemplateArg();
+        if (E == nullptr)
+          return E;
+        Names.push_back(E);
+      }
     }
     return make<CallExpr>(Name, popTrailingNodeArray(ExprsBegin));
   }