[clang] [clang][Index] check `TemplateTypeParmTypeLoc ::getDecl()` against `nullptr` in `TypeIndexer` and `CursorVisitor` (PR #89392)

[Julian Schmidt via cfe-commits]

https://github.com/5chmidti created https://github.com/llvm/llvm-project/pull/89392

In the added testcase, which is invalid code, the result of `getDecl()` called on a `TemplateTypeParmTypeLoc` was
a `nullptr`. However, `IndexingContext::handleReference` expects the parameter `D` to not be a `nullptr` and
passed it to `isa<>` without checking it. Similarly `MakeCursorTypeRef` expects `D` to not be a `nullptr` as well.

Fixes: clangd/clangd#2016, #89389


>From 2ebb3ec2f0f654b39283947e39adf182fc799683 Mon Sep 17 00:00:00 2001
From: Julian Schmidt <git.julian.schmidt at gmail.com>
Date: Fri, 19 Apr 2024 16:41:50 +0200
Subject: [PATCH] [clang][Index] check `TemplateTypeParmTypeLoc ::getDecl()`
 against `nullptr` in `TypeIndexer` and `CursorVisitor`

In the added testcase, which is invalid code, the result of `getDecl()` called on a `TemplateTypeParmTypeLoc` was
a `nullptr`. However, `IndexingContext::handleReference` expects the parameter `D` to not be a `nullptr` and
passed it to `isa<>` without checking it. Similarly `MakeCursorTypeRef` expects `D` to not be a `nullptr` as well.

Fixes: clangd/clangd#2016, #89389
---
 clang/lib/Index/IndexTypeSourceInfo.cpp |  3 +++
 clang/test/Index/gh89389.cpp            | 16 +++++++++++++++
 clang/tools/libclang/CIndex.cpp         |  8 ++++++--
 clang/unittests/Index/IndexTests.cpp    | 27 +++++++++++++++++++++++++
 4 files changed, 52 insertions(+), 2 deletions(-)
 create mode 100644 clang/test/Index/gh89389.cpp

diff --git a/clang/lib/Index/IndexTypeSourceInfo.cpp b/clang/lib/Index/IndexTypeSourceInfo.cpp
index b986ccde574525..58ad0799062ca3 100644
--- a/clang/lib/Index/IndexTypeSourceInfo.cpp
+++ b/clang/lib/Index/IndexTypeSourceInfo.cpp
@@ -52,6 +52,9 @@ class TypeIndexer : public RecursiveASTVisitor<TypeIndexer> {
   bool VisitTemplateTypeParmTypeLoc(TemplateTypeParmTypeLoc TTPL) {
     SourceLocation Loc = TTPL.getNameLoc();
     TemplateTypeParmDecl *TTPD = TTPL.getDecl();
+    if (!TTPD)
+      return false;
+
     return IndexCtx.handleReference(TTPD, Loc, Parent, ParentDC,
                                     SymbolRoleSet());
   }
diff --git a/clang/test/Index/gh89389.cpp b/clang/test/Index/gh89389.cpp
new file mode 100644
index 00000000000000..0458d0a64083d8
--- /dev/null
+++ b/clang/test/Index/gh89389.cpp
@@ -0,0 +1,16 @@
+// RUN: c-index-test -test-load-source all %s -std=gnu++20 -fno-delayed-template-parsing
+
+namespace test18 {
+template<typename T>
+concept False = false;
+
+template <typename T> struct Foo { T t; };
+
+template<typename T> requires False<T>
+Foo(T) -> Foo<int>;
+
+template <typename U>
+using Bar = Foo<U>;
+
+Bar s = {1};
+} // namespace test18
diff --git a/clang/tools/libclang/CIndex.cpp b/clang/tools/libclang/CIndex.cpp
index cbc1d85bb33dfc..8fd723a90e5565 100644
--- a/clang/tools/libclang/CIndex.cpp
+++ b/clang/tools/libclang/CIndex.cpp
@@ -1693,12 +1693,16 @@ bool CursorVisitor::VisitTagTypeLoc(TagTypeLoc TL) {
 }
 
 bool CursorVisitor::VisitTemplateTypeParmTypeLoc(TemplateTypeParmTypeLoc TL) {
-  if (const auto *TC = TL.getDecl()->getTypeConstraint()) {
+  TemplateTypeParmDecl *D = TL.getDecl();
+  if (!D)
+    return true;
+
+  if (const auto *TC = D->getTypeConstraint()) {
     if (VisitTypeConstraint(*TC))
       return true;
   }
 
-  return Visit(MakeCursorTypeRef(TL.getDecl(), TL.getNameLoc(), TU));
+  return Visit(MakeCursorTypeRef(D, TL.getNameLoc(), TU));
 }
 
 bool CursorVisitor::VisitObjCInterfaceTypeLoc(ObjCInterfaceTypeLoc TL) {
diff --git a/clang/unittests/Index/IndexTests.cpp b/clang/unittests/Index/IndexTests.cpp
index 8e9a1c6bf88245..0db8a4b98c2025 100644
--- a/clang/unittests/Index/IndexTests.cpp
+++ b/clang/unittests/Index/IndexTests.cpp
@@ -453,6 +453,33 @@ TEST(IndexTest, ReadWriteRoles) {
                            WrittenAt(Position(6, 17))))));
 }
 
+TEST(IndexTest, gh89389) {
+  std::string Code = R"cpp(
+    namespace test18 {
+    template<typename T>
+    concept False = false;
+
+    template <typename T> struct Foo { T t; };
+
+    template<typename T> requires False<T>
+    Foo(T) -> Foo<int>;
+
+    template <typename U>
+    using Bar = Foo<U>;
+
+    Bar s = {1};
+    } // namespace test18
+  )cpp";
+  auto Index = std::make_shared<Indexer>();
+  IndexingOptions Opts;
+  Opts.IndexTemplateParameters = true;
+
+  // This test case is invalid code, so the expected return value is `false`.
+  // What is being tested is that there is no crash.
+  EXPECT_FALSE(tooling::runToolOnCodeWithArgs(
+      std::make_unique<IndexAction>(Index, Opts), Code, {"-std=c++20"}));
+}
+
 } // namespace
 } // namespace index
 } // namespace clang