[clang-tools-extra] [clang-tidy] add new check readability-enum-initial-value (PR #86129)

[Piotr Zegar via cfe-commits]

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@@ -0,0 +1,82 @@
+//===--- EnumInitialValueCheck.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 "EnumInitialValueCheck.h"
+#include "../utils/LexerUtils.h"
+#include "clang/AST/Decl.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/Basic/Diagnostic.h"
+#include "llvm/ADT/SmallString.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::readability {
+
+namespace {
+
+AST_MATCHER(EnumDecl, isNoneEnumeratorsInitialized) {
+  return llvm::all_of(Node.enumerators(), [](EnumConstantDecl const *ECD) {
+    return ECD->getInitExpr() == nullptr;
+  });
+}
+
+AST_MATCHER(EnumDecl, isOnlyFirstEnumeratorsInitialized) {
+  for (EnumConstantDecl const *ECD : Node.enumerators())
+    if (ECD == *Node.enumerator_begin()) {
+      if (ECD->getInitExpr() == nullptr)
+        return false;
+    } else {
+      if (ECD->getInitExpr() != nullptr)
+        return false;
+    }
+  return true;
+}
+
+AST_MATCHER(EnumDecl, isAllEnumeratorsInitialized) {
+  return llvm::all_of(Node.enumerators(), [](EnumConstantDecl const *ECD) {
+    return ECD->getInitExpr() != nullptr;
+  });
+}
+
+} // namespace
+
+void EnumInitialValueCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(enumDecl(unless(anyOf(isNoneEnumeratorsInitialized(),
+                                           isOnlyFirstEnumeratorsInitialized(),
+                                           isAllEnumeratorsInitialized())))
+                         .bind("enum"),
+                     this);
+}
+
+void EnumInitialValueCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *Enum = Result.Nodes.getNodeAs<EnumDecl>("enum");
+  assert(Enum != nullptr);
+  SourceLocation Loc = Enum->getBeginLoc();
+  if (Loc.isInvalid() || Loc.isMacroID())
+    return;
+  DiagnosticBuilder Diag =
+      diag(Loc, "inital value in enum %0 has readability issue, "
----------------
PiotrZSL wrote:

no need to mention "readability issue", better would be to say that Enum initialization is not consistent , and "initialize first, all or none"

https://github.com/llvm/llvm-project/pull/86129