From 225b91e6cbba31ff1ce787a152a67977d08fdcab 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: [PATCH] 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.
---
 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 32ca7643a760..d2feb1c10f06 100644
--- a/clang/lib/AST/TypePrinter.cpp
+++ b/clang/lib/AST/TypePrinter.cpp
@@ -1467,8 +1467,7 @@ 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 7b44b1ecece2..12801a701812 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>