From cca10be3f60dd30055acc70d117649f889da779d Mon Sep 17 00:00:00 2001
From: Adam Czachorowski <adamcz@google.com>
Date: Wed, 8 Apr 2020 13:42:10 +0200
Subject: [PATCH] [clangd] Fix a crash bug in AddUsing tweak around template
 handling.

Summary:
The crash happened on cases like:
template<typename TT> using one = two::three<T^T>;
because we tried to call getName() on getBaseTypeIdentifier(), which can
be nullptr.

Ideally we would support this use case as well, but for now not crashing
will do.

Reviewers: sammccall

Reviewed By: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D77656
---
 clang-tools-extra/clangd/refactor/tweaks/AddUsing.cpp | 8 +++++---
 clang-tools-extra/clangd/unittests/TweakTests.cpp     | 5 +++++
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/clang-tools-extra/clangd/refactor/tweaks/AddUsing.cpp b/clang-tools-extra/clangd/refactor/tweaks/AddUsing.cpp
index 411c685e2b7d..f2ef235c43f7 100644
--- a/clang-tools-extra/clangd/refactor/tweaks/AddUsing.cpp
+++ b/clang-tools-extra/clangd/refactor/tweaks/AddUsing.cpp
@@ -206,9 +206,11 @@ bool AddUsing::prepare(const Selection &Inputs) {
     Name = D->getDecl()->getName();
   } else if (auto *T = Node->ASTNode.get<TypeLoc>()) {
     if (auto E = T->getAs<ElaboratedTypeLoc>()) {
-      QualifierToRemove = E.getQualifierLoc();
-      Name =
-          E.getType().getUnqualifiedType().getBaseTypeIdentifier()->getName();
+      if (auto *BaseTypeIdentifier =
+              E.getType().getUnqualifiedType().getBaseTypeIdentifier()) {
+        Name = BaseTypeIdentifier->getName();
+        QualifierToRemove = E.getQualifierLoc();
+      }
     }
   }
 
diff --git a/clang-tools-extra/clangd/unittests/TweakTests.cpp b/clang-tools-extra/clangd/unittests/TweakTests.cpp
index 979ee44f4474..b93cca23e6b6 100644
--- a/clang-tools-extra/clangd/unittests/TweakTests.cpp
+++ b/clang-tools-extra/clangd/unittests/TweakTests.cpp
@@ -2436,6 +2436,7 @@ TEST_F(AddUsingTest, Prepare) {
 #define NS(name) one::two::name
 namespace one {
 void oo() {}
+template<typename TT> class tt {};
 namespace two {
 enum ee {};
 void ff() {}
@@ -2458,6 +2459,10 @@ public:
   EXPECT_UNAVAILABLE(Header +
                      "void fun() { o^n^e^:^:^t^w^o^:^:^c^c^:^:^s^t inst; }");
   EXPECT_UNAVAILABLE(Header + "void fun() { N^S(c^c) inst; }");
+  // This used to crash. Ideally we would support this case, but for now we just
+  // test that we don't crash.
+  EXPECT_UNAVAILABLE(Header +
+                     "template<typename TT> using foo = one::tt<T^T>;");
 }
 
 TEST_F(AddUsingTest, Apply) {
-- 
2.34.1