[clang-tools-extra] [clang-tidy] Fix false positive in cert-ctr56-cpp(PointerArithmeticOnPolymorphicObjectCheck) (PR #187452)

[via cfe-commits]

https://github.com/IamYJLee created https://github.com/llvm/llvm-project/pull/187452

## Summary
This change adds `unless(isInstantiationDependent())` to the `ArraySubscript` matcher.

## Motivation
In template code, some array subscript expressions are not fully resolved yet.
Because of this, the matcher may treat them incorrectly and produce false positives.

## Change
This patch skips instantiation-dependent expressions in templates. 
It helps the matcher work only on resolved expressions.

Closes https://github.com/llvm/llvm-project/issues/187009.

>From 44205cbf91abd508c2f8737811d96458cb9e5a5c Mon Sep 17 00:00:00 2001
From: LeeYoungJoon <dog3hk.dev at gmail.com>
Date: Thu, 19 Mar 2026 16:39:14 +0900
Subject: [PATCH] [clang-tidy] Fix false positive in
 cert-ctr56-cpp(PointerArithmeticOnPolymorphicObjectCheck)

- Add 'unless(isInstantiationDependent())' to the ArraySubscript matcher to skip expressions that are not yet resolved in templates.
---
 .../bugprone/PointerArithmeticOnPolymorphicObjectCheck.cpp     | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/clang-tools-extra/clang-tidy/bugprone/PointerArithmeticOnPolymorphicObjectCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/PointerArithmeticOnPolymorphicObjectCheck.cpp
index c21abad947912..ac886143b8d98 100644
--- a/clang-tools-extra/clang-tidy/bugprone/PointerArithmeticOnPolymorphicObjectCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/PointerArithmeticOnPolymorphicObjectCheck.cpp
@@ -53,7 +53,8 @@ void PointerArithmeticOnPolymorphicObjectCheck::registerMatchers(
                                        ? PointerExprWithVirtualMethod
                                        : PolymorphicPointerExpr;
 
-  const auto ArraySubscript = arraySubscriptExpr(hasBase(SelectedPointerExpr));
+  const auto ArraySubscript = expr(arraySubscriptExpr(hasBase(SelectedPointerExpr)),
+                                   unless(isInstantiationDependent()));
 
   const auto BinaryOperators =
       binaryOperator(hasAnyOperatorName("+", "-", "+=", "-="),