[clang-tools-extra] [clang-tidy] Add new check bugprone-tagged-union-member-count (PR #89925)

[Piotr Zegar via cfe-commits]

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@@ -0,0 +1,125 @@
+//===--- TaggedUnionMemberCountCheck.cpp - clang-tidy ---------------------===//
+//
+// 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 "TaggedUnionMemberCountCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/Expr.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+#include "clang/AST/PrettyPrinter.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/Support/Casting.h"
+#include <limits>
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::bugprone {
+
+void TaggedUnionMemberCountCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      recordDecl(
+          allOf(isStruct(),
+                has(fieldDecl(hasType(recordDecl(isUnion()).bind("union")))),
+                has(fieldDecl(hasType(enumDecl().bind("tags"))))))
+          .bind("root"),
+      this);
+}
+
+static bool hasMultipleUnionsOrEnums(const RecordDecl *rec) {
+  int tags = 0;
+  int unions = 0;
+  for (const FieldDecl *r : rec->fields()) {
+    TypeSourceInfo *info = r->getTypeSourceInfo();
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PiotrZSL wrote:

per codding standard local variables should be CammelCase

https://github.com/llvm/llvm-project/pull/89925