[clang] Fix a bug with the hasAncestor AST matcher when a node has several parents without pointer identity (PR #118511)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Loïc Joly (loic-joly-sonarsource)

<details>
<summary>Changes</summary>

Before the change, getMemoizationData is used as a key to stop visiting the parents, but if a node has no identity, this is nullptr, which means that the visit will stop as soon as a second node with no identity is visited.

---
Full diff: https://github.com/llvm/llvm-project/pull/118511.diff


2 Files Affected:

- (modified) clang/lib/ASTMatchers/ASTMatchFinder.cpp (+2-1) 
- (modified) clang/unittests/ASTMatchers/ASTMatchersTraversalTest.cpp (+18) 


``````````diff
diff --git a/clang/lib/ASTMatchers/ASTMatchFinder.cpp b/clang/lib/ASTMatchers/ASTMatchFinder.cpp
index 3d01a70395a9bb..a7ef5ae6949537 100644
--- a/clang/lib/ASTMatchers/ASTMatchFinder.cpp
+++ b/clang/lib/ASTMatchers/ASTMatchFinder.cpp
@@ -1237,7 +1237,8 @@ class MatchASTVisitor : public RecursiveASTVisitor<MatchASTVisitor>,
           // Make sure we do not visit the same node twice.
           // Otherwise, we'll visit the common ancestors as often as there
           // are splits on the way down.
-          if (Visited.insert(Parent.getMemoizationData()).second)
+          if (Parent.getMemoizationData() == nullptr ||
+            Visited.insert(Parent.getMemoizationData()).second)
             Queue.push_back(Parent);
         }
         Queue.pop_front();
diff --git a/clang/unittests/ASTMatchers/ASTMatchersTraversalTest.cpp b/clang/unittests/ASTMatchers/ASTMatchersTraversalTest.cpp
index 1d18869a6b8afc..17b058e4783018 100644
--- a/clang/unittests/ASTMatchers/ASTMatchersTraversalTest.cpp
+++ b/clang/unittests/ASTMatchers/ASTMatchersTraversalTest.cpp
@@ -5536,6 +5536,24 @@ TEST(HasAncestor, MatchesInImplicitCode) {
         hasAncestor(recordDecl(hasName("A")))))))));
 }
 
+TEST(HasAncestor, MatchesWithMultipleParentsWithoutPointerIdentity) {
+    EXPECT_TRUE(matches(
+    R"cpp(
+template <int i> class Fact {};
+template <class T> class W {};
+template <class T> struct A
+{
+    static void f() {
+        W<Fact<12>> fact12;
+    }
+};
+void f() {
+    A<int>::f();
+    A<double>::f();
+})cpp",
+    integerLiteral(hasAncestor(functionDecl()))));
+}
+
 TEST(HasParent, MatchesOnlyParent) {
   EXPECT_TRUE(matches(
     "void f() { if (true) { int x = 42; } }",

``````````

</details>


https://github.com/llvm/llvm-project/pull/118511