[clang] Fix false match on nullPointerConstant for array indices (PR #201893)

[Kay Hicketts via cfe-commits]

https://github.com/KHicketts updated https://github.com/llvm/llvm-project/pull/201893

>From f238457992ea5315c63430927c39c1d1c8d494dd Mon Sep 17 00:00:00 2001
From: khickett <khicketts at bloomberg.net>
Date: Fri, 5 Jun 2026 18:03:02 +0100
Subject: [PATCH 1/3] Fix false match on nullPointerConstant for array indices

---
 clang/include/clang/ASTMatchers/ASTMatchers.h            | 2 +-
 clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/clang/include/clang/ASTMatchers/ASTMatchers.h b/clang/include/clang/ASTMatchers/ASTMatchers.h
index bc0f35898a2c9..24d9eea98df9b 100644
--- a/clang/include/clang/ASTMatchers/ASTMatchers.h
+++ b/clang/include/clang/ASTMatchers/ASTMatchers.h
@@ -8369,7 +8369,7 @@ extern const internal::VariadicDynCastAllOfMatcher<Stmt, CUDAKernelCallExpr>
 AST_MATCHER_FUNCTION(internal::Matcher<Expr>, nullPointerConstant) {
   return anyOf(
       gnuNullExpr(), cxxNullPtrLiteralExpr(),
-      integerLiteral(equals(0), hasParent(expr(hasType(pointerType())))));
+      integerLiteral(equals(0), hasParent(castExpr(hasCastKind(CK_NullToPointer)))));
 }
 
 /// Matches the DecompositionDecl the binding belongs to.
diff --git a/clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp b/clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp
index d9647c201fc30..d51f70b867ac9 100644
--- a/clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp
+++ b/clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp
@@ -4049,6 +4049,7 @@ TEST_P(ASTMatchersTest, NullPointerConstant) {
   EXPECT_TRUE(matches("char *cp = (char *)0;", expr(nullPointerConstant())));
   EXPECT_TRUE(matches("int *ip = 0;", expr(nullPointerConstant())));
   EXPECT_FALSE(matches("int i = 0;", expr(nullPointerConstant())));
+  EXPECT_FALSE(matches("int *p[1]; (void)p[0];", expr(nullPointerConstant())));
 }
 
 TEST_P(ASTMatchersTest, NullPointerConstant_GNUNull) {

>From 22f22c2dd231d97f1fa95712c809e93287896a07 Mon Sep 17 00:00:00 2001
From: khickett <khicketts at bloomberg.net>
Date: Thu, 18 Jun 2026 15:32:40 +0100
Subject: [PATCH 2/3] add release note

---
 clang/docs/ReleaseNotes.rst | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 8a6eb2003e5f0..be1a889019b0d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -980,6 +980,8 @@ AST Matchers
 ------------
 - Add ``functionTypeLoc`` matcher for matching ``FunctionTypeLoc``.
 - Add missing support for ``TraversalKind`` in some ``addMatcher()`` overloads.
+- Fixed ``nullPointerConstant`` matcher falsely matching integer literal ``0``
+  when used as an array subscript index.
 
 clang-format
 ------------

>From a0a0813e92e0ade4900e5be671cac9039c1cd1a8 Mon Sep 17 00:00:00 2001
From: khickett <khicketts at bloomberg.net>
Date: Wed, 24 Jun 2026 16:27:50 +0100
Subject: [PATCH 3/3] clang format

---
 clang/include/clang/ASTMatchers/ASTMatchers.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/clang/include/clang/ASTMatchers/ASTMatchers.h b/clang/include/clang/ASTMatchers/ASTMatchers.h
index 24d9eea98df9b..8108ee559acea 100644
--- a/clang/include/clang/ASTMatchers/ASTMatchers.h
+++ b/clang/include/clang/ASTMatchers/ASTMatchers.h
@@ -8367,9 +8367,9 @@ extern const internal::VariadicDynCastAllOfMatcher<Stmt, CUDAKernelCallExpr>
 ///   matches the initializer for v1, v2, v3, cp, and ip. Does not match the
 ///   initializer for i.
 AST_MATCHER_FUNCTION(internal::Matcher<Expr>, nullPointerConstant) {
-  return anyOf(
-      gnuNullExpr(), cxxNullPtrLiteralExpr(),
-      integerLiteral(equals(0), hasParent(castExpr(hasCastKind(CK_NullToPointer)))));
+  return anyOf(gnuNullExpr(), cxxNullPtrLiteralExpr(),
+               integerLiteral(equals(0), hasParent(castExpr(
+                                             hasCastKind(CK_NullToPointer)))));
 }
 
 /// Matches the DecompositionDecl the binding belongs to.