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

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In-Reply-To: <llvm.org/llvm/llvm-project/pull/89925 at github.com>


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@@ -0,0 +1,192 @@
+//===--- 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 "../utils/OptionsUtils.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallSet.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::bugprone {
+
+static constexpr llvm::StringLiteral StrictModeOptionName = "StrictMode";
+static constexpr llvm::StringLiteral EnableCountingEnumHeuristicOptionName =
+    "EnableCountingEnumHeuristic";
+static constexpr llvm::StringLiteral CountingEnumPrefixesOptionName =
+    "CountingEnumPrefixes";
+static constexpr llvm::StringLiteral CountingEnumSuffixesOptionName =
+    "CountingEnumSuffixes";
+
+static constexpr bool StrictModeOptionDefaultValue = false;
+static constexpr bool EnableCountingEnumHeuristicOptionDefaultValue = true;
+static constexpr llvm::StringLiteral CountingEnumPrefixesOptionDefaultValue =
+    "";
+static constexpr llvm::StringLiteral CountingEnumSuffixesOptionDefaultValue =
+    "count";
+
+static constexpr llvm::StringLiteral RootMatchBindName = "root";
+static constexpr llvm::StringLiteral UnionMatchBindName = "union";
+static constexpr llvm::StringLiteral TagMatchBindName = "tags";
+
+namespace {
+AST_MATCHER(FieldDecl, isUnion) {
+  const Type *T = Node.getType().getCanonicalType().getTypePtr();
+  assert(T);
+  return T->isUnionType();
+}
+
+AST_MATCHER(FieldDecl, isEnum) {
+  const Type *T = Node.getType().getCanonicalType().getTypePtr();
+  assert(T);
+  return T->isEnumeralType();
+}
+
+AST_MATCHER_P2(RecordDecl, fieldCountOfKindIsGT,
+               ast_matchers::internal::Matcher<FieldDecl>, InnerMatcher,
+               unsigned, N) {
+  unsigned matchCount = 0;
+  for (const auto field : Node.fields()) {
+    if (InnerMatcher.matches(*field, Finder, Builder)) {
+      matchCount += 1;
+    }
+  }
+  return matchCount > N;
+}
+}; // namespace
+
+TaggedUnionMemberCountCheck::TaggedUnionMemberCountCheck(
+    StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      StrictMode(
+          Options.get(StrictModeOptionName, StrictModeOptionDefaultValue)),
+      EnableCountingEnumHeuristic(
+          Options.get(EnableCountingEnumHeuristicOptionName,
+                      EnableCountingEnumHeuristicOptionDefaultValue)),
+      CountingEnumPrefixes(utils::options::parseStringList(
+          Options.get(CountingEnumPrefixesOptionName,
+                      CountingEnumPrefixesOptionDefaultValue))),
+      CountingEnumSuffixes(utils::options::parseStringList(
+          Options.get(CountingEnumSuffixesOptionName,
+                      CountingEnumSuffixesOptionDefaultValue))) {
+  if (!EnableCountingEnumHeuristic) {
+    if (Options.get(CountingEnumPrefixesOptionName))
+      configurationDiag("%0: Counting enum heuristic is disabled but "
+                        "%1 is set")
+          << Name << CountingEnumPrefixesOptionName;
+    if (Options.get(CountingEnumSuffixesOptionName))
+      configurationDiag("%0: Counting enum heuristic is disabled but "
+                        "%1 is set")
+          << Name << CountingEnumSuffixesOptionName;
+  }
+}
+
+void TaggedUnionMemberCountCheck::storeOptions(
+    ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, StrictModeOptionName, StrictMode);
+  Options.store(Opts, EnableCountingEnumHeuristicOptionName,
+                EnableCountingEnumHeuristic);
+  Options.store(Opts, CountingEnumPrefixesOptionName,
+                utils::options::serializeStringList(CountingEnumPrefixes));
+  Options.store(Opts, CountingEnumSuffixesOptionName,
+                utils::options::serializeStringList(CountingEnumSuffixes));
+}
+
+void TaggedUnionMemberCountCheck::registerMatchers(MatchFinder *Finder) {
+
+  static const auto hasMultipleUnionsOrEnums = anyOf(
+      fieldCountOfKindIsGT(isUnion(), 1), fieldCountOfKindIsGT(isEnum(), 1));
+
+  Finder->addMatcher(
+      recordDecl(anyOf(isStruct(), isClass()),
+                 unless(anyOf(isImplicit(), hasMultipleUnionsOrEnums)),
+                 has(fieldDecl(isUnion()).bind(UnionMatchBindName)),
+                 has(fieldDecl(isEnum()).bind(TagMatchBindName)))
+          .bind(RootMatchBindName),
+      this);
+}
+
+bool TaggedUnionMemberCountCheck::isCountingEnumLikeName(StringRef Name) const {
+  if (llvm::any_of(CountingEnumPrefixes, [Name](StringRef Prefix) -> bool {
+        return Name.starts_with_insensitive(Prefix);
+      }))
+    return true;
+  if (llvm::any_of(CountingEnumSuffixes, [Name](StringRef Suffix) -> bool {
+        return Name.ends_with_insensitive(Suffix);
+      }))
+    return true;
+  return false;
+}
+
+std::pair<const std::size_t, const EnumConstantDecl *>
+TaggedUnionMemberCountCheck::getNumberOfEnumValues(const EnumDecl *ED) {
+  llvm::SmallSet<llvm::APSInt, 32> EnumValues;
+
+  const EnumConstantDecl *LastEnumConstant = nullptr;
+  for (const auto Enumerator : ED->enumerators()) {
+    EnumValues.insert(Enumerator->getInitVal());
+    LastEnumConstant = Enumerator;
+  }
+
+  if (EnableCountingEnumHeuristic && LastEnumConstant) {
+    if (isCountingEnumLikeName(LastEnumConstant->getName())) {
+      if (LastEnumConstant->getInitVal() == (EnumValues.size() - 1)) {
+        return {EnumValues.size() - 1, LastEnumConstant};
+      }
+    }
+  }
----------------
whisperity wrote:

```suggestion
  if (EnableCountingEnumHeuristic && LastEnumConstant &&
      isCountingEnumLikeName(LastEnumConstant->getName()) &&
      (LastEnumConstant->getInitVal() == EnumValues.size() - 1))
    return {EnumValues.size() - 1, LastEnumConstant};
```

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