Fix crash getting name of a template decl

NamedDecl::getIdentifier can return a nullptr when
DeclarationName::isIdentifier is false, which leads to a null pointer
dereference when TypePrinter::printTemplateId calls ->getName().

NamedDecl::getName does the same thing in the successful case and
returns an empty string in the failure case.

This crash affects the llvm 14 packages on llvm.org.

(cherry picked from commit 225b91e)

Author: tblah

clang/lib/AST/TypePrinter.cpp

@@ -1466,8 +1466,7 @@ void TypePrinter::printTemplateId(const TemplateSpecializationType *T,
     if (!Policy.SuppressScope)
       AppendScope(TD->getDeclContext(), OS, TD->getDeclName());
 
-    IdentifierInfo *II = TD->getIdentifier();
-    OS << II->getName();
+    OS << TD->getName();
   } else {
     T->getTemplateName().print(OS, Policy);
   }

clang/unittests/AST/TypePrinterTest.cpp

@@ -64,6 +64,22 @@ TEST(TypePrinter, TemplateId) {
       [](PrintingPolicy &Policy) { Policy.FullyQualifiedName = true; }));
 }
 
+TEST(TypePrinter, TemplateId2) {
+  std::string Code = R"cpp(
+      template <template <typename ...> class TemplatedType>
+      void func(TemplatedType<int> Param);
+    )cpp";
+  auto Matcher = parmVarDecl(hasType(qualType().bind("id")));
+
+  // Regression test ensuring we do not segfault getting the QualType as a
+  // string.
+  ASSERT_TRUE(PrintedTypeMatches(Code, {}, Matcher, "<int>",
+                                 [](PrintingPolicy &Policy) {
+                                   Policy.FullyQualifiedName = true;
+                                   Policy.PrintCanonicalTypes = true;
+                                 }));
+}
+
 TEST(TypePrinter, ParamsUglified) {
   llvm::StringLiteral Code = R"cpp(
     template <typename _Tp, template <typename> class __f>