[clang-tools-extra] [clang-tidy] Support C++26 placeholder bindings (PR #207604)

[Yanzuo Liu via cfe-commits]

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@@ -0,0 +1,76 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "UsePlaceholderBindingCheck.h"
+#include "../utils/DeclRefExprUtils.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::modernize {
+
+namespace {
+AST_POLYMORPHIC_MATCHER(isInMacro,
+                        AST_POLYMORPHIC_SUPPORTED_TYPES(Stmt, Decl)) {
+  return Node.getBeginLoc().isMacroID() || Node.getEndLoc().isMacroID();
+}
+
+AST_MATCHER(VarDecl, hasAutomaticStorageDurationAndNoSpecifiers) {
+  return !Node.hasAttrs() && Node.getStorageClass() == SC_None &&
+         Node.getTSCSpec() == TSCS_unspecified;
+}
+} // namespace
+
+void UsePlaceholderBindingCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      cStyleCastExpr(
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zwuis wrote:

Use `explicitCastExpr` to match `void(x)` and `static_cast<void>(x)`.

https://github.com/llvm/llvm-project/pull/207604