From 3bfae7816bdb5b09930f073f1eb99f72015d9f78 Mon Sep 17 00:00:00 2001
From: Tom Eccles <tom.eccles@codethink.co.uk>
Date: Fri, 22 Apr 2022 13:03:28 -0400
Subject: 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 225b91e6cbba31ff1ce787a152a67977d08fdcab)
---
 clang/lib/AST/TypePrinter.cpp           |  3 +--
 clang/unittests/AST/TypePrinterTest.cpp | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/clang/lib/AST/TypePrinter.cpp b/clang/lib/AST/TypePrinter.cpp
index bba323f651aa..6e827530f41b 100644
--- a/clang/lib/AST/TypePrinter.cpp
+++ b/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);
   }
diff --git a/clang/unittests/AST/TypePrinterTest.cpp b/clang/unittests/AST/TypePrinterTest.cpp
index 8500d518d25f..d60ecedea95f 100644
--- a/clang/unittests/AST/TypePrinterTest.cpp
+++ b/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>
-- 
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