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

[via cfe-commits]

================
@@ -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();
+    QualType qualtype = info->getType();
+    const Type *type = qualtype.getTypePtr();
+    if (type->isUnionType())
+      unions += 1;
+    else if (type->isEnumeralType())
+      tags += 1;
+    if (tags > 1 || unions > 1)
+      return true;
+  }
----------------
isuckatcs wrote:

How about this simplified version instead?
```suggestion
static bool hasMultipleUnionsOrEnums(const RecordDecl *rec) {
  size_t Enums = 0;
  size_t Unions = 0;

  for(const auto&& Field : rec->fields()) {
    QualType Type = Field->getType();

    Enums += Type->isEnumeralType();
    Unions += Type->isUnionType();
  }

  return Enums > 1 || Unions > 1;
  }
```

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