[clang] [-Wunsafe-buffer-usage] Ignore constant safe indices in array subscripts (PR #80504)

[via cfe-commits]

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@@ -406,6 +406,31 @@ AST_MATCHER(CXXConstructExpr, isSafeSpanTwoParamConstruct) {
   }
   return false;
 }
+
+AST_MATCHER(ArraySubscriptExpr, isSafeArraySubscript) {
+  const DeclRefExpr * BaseDRE = dyn_cast_or_null<DeclRefExpr>(Node.getBase()->IgnoreParenImpCasts());
+  if (!BaseDRE)
+    return false;
+  if (!BaseDRE->getDecl())
+    return false;
+  auto BaseVarDeclTy = BaseDRE->getDecl()->getType();
+  if (!BaseVarDeclTy->isConstantArrayType())
+    return false;
+  const auto * CATy = dyn_cast_or_null<ConstantArrayType>(BaseVarDeclTy);
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jkorous-apple wrote:

Take a look getAsConstantArrayType().

https://github.com/llvm/llvm-project/pull/80504