[clang-tools-extra] [clang-tidy] Add modernize-use-to-underlying check (PR #210459)

[Baranov Victor via cfe-commits]

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@@ -0,0 +1,158 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "UseToUnderlyingCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Tooling/FixIt.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy {
+
+template <>
+struct OptionEnumMapping<modernize::UseToUnderlyingCheck::ImpreciseCastsKind> {
+  static llvm::ArrayRef<
+      std::pair<modernize::UseToUnderlyingCheck::ImpreciseCastsKind, StringRef>>
+  getEnumMapping() {
+    using ImpreciseCastsKind =
+        modernize::UseToUnderlyingCheck::ImpreciseCastsKind;
+    static constexpr std::pair<ImpreciseCastsKind, StringRef> Mapping[] = {
+        {ImpreciseCastsKind::Ignore, "Ignore"},
+        {ImpreciseCastsKind::Warn, "Warn"},
+        {ImpreciseCastsKind::PreserveType, "PreserveType"},
+        {ImpreciseCastsKind::UseUnderlyingType, "UseUnderlyingType"},
+    };
+    return {Mapping};
+  }
+};
+
+} // namespace clang::tidy
+
+namespace clang::tidy::modernize {
+
+UseToUnderlyingCheck::UseToUnderlyingCheck(StringRef Name,
+                                           ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      ImpreciseCasts(Options.get("ImpreciseCasts", ImpreciseCastsKind::Warn)),
+      ReplacementFunction(
+          Options.get("ReplacementFunction", "std::to_underlying")),
+      ReplacementFunctionHeader(Options.get("ReplacementFunctionHeader", "")),
+      IncludeInserter(Options.getLocalOrGlobal("IncludeStyle",
+                                               utils::IncludeSorter::IS_LLVM),
+                      areDiagsSelfContained()) {
+  if (ReplacementFunction == "std::to_underlying") {
+    if (ReplacementFunctionHeader.empty())
+      ReplacementFunctionHeader = "<utility>";
+    else if (ReplacementFunctionHeader != "<utility>")
+      configurationDiag("'std::to_underlying' is declared in '<utility>', but "
+                        "'ReplacementFunctionHeader' is set to '%0'")
+          << ReplacementFunctionHeader;
+  }
+}
+
+bool UseToUnderlyingCheck::isLanguageVersionSupported(
+    const LangOptions &LangOpts) const {
+  // std::to_underlying is a C++23 library facility, but a user-provided
+  // replacement (e.g. llvm::to_underlying) only requires scoped enumerations,
+  // which are available since C++11.
+  if (ReplacementFunction == "std::to_underlying")
+    return LangOpts.CPlusPlus23;
+  return LangOpts.CPlusPlus11;
+}
+
+void UseToUnderlyingCheck::registerPPCallbacks(const SourceManager &SM,
+                                               Preprocessor *PP,
+                                               Preprocessor *ModuleExpanderPP) {
+  IncludeInserter.registerPreprocessor(PP);
+}
+
+void UseToUnderlyingCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "ImpreciseCasts", ImpreciseCasts);
+  Options.store(Opts, "ReplacementFunction", ReplacementFunction);
+  Options.store(Opts, "IncludeStyle", IncludeInserter.getStyle());
+  Options.store(Opts, "ReplacementFunctionHeader", ReplacementFunctionHeader);
+}
+
+void UseToUnderlyingCheck::registerMatchers(MatchFinder *Finder) {
+  // Match an explicit cast (``static_cast``, C-style or functional) from a
+  // scoped enumeration to an integer type. Enum-to-enum casts and casts to a
+  // floating-point or pointer type are excluded here; whether the conversion is
+  // precise or imprecise is decided in check().
+  Finder->addMatcher(
+      explicitCastExpr(
+          hasDestinationType(
+              qualType(isInteger(), unless(hasCanonicalType(enumType())))),
+          hasSourceExpression(
+              expr(hasType(hasCanonicalType(enumType(
+                       hasDeclaration(enumDecl(isScoped()).bind("enum"))))))
+                  .bind("operand")))
+          .bind("cast"),
+      this);
+}
+
+void UseToUnderlyingCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *Cast = Result.Nodes.getNodeAs<ExplicitCastExpr>("cast");
+  const auto *Operand = Result.Nodes.getNodeAs<Expr>("operand");
+  const auto *Enum = Result.Nodes.getNodeAs<EnumDecl>("enum");
+
+  const QualType DestType = Cast->getType().getCanonicalType();
+  const QualType UnderlyingType =
+      Enum->getIntegerType().getCanonicalType().getUnqualifiedType();
+  const QualType DestUnqualified = DestType.getUnqualifiedType();
+  const bool IsPrecise = UnderlyingType == DestUnqualified;
+
+  // A cast to ``bool`` that is not precise (i.e. the underlying type is not
+  // ``bool``) expresses a truthiness test rather than a request for the
+  // underlying value, so it is left untouched.
+  if (DestType->isBooleanType() && !IsPrecise)
+    return;
+
+  // Ignore imprecise casts if asked to do so.
+  if (!IsPrecise && ImpreciseCasts == ImpreciseCastsKind::Ignore)
+    return;
+
+  auto Diag = diag(Cast->getBeginLoc(),
+                   "use '%0' to convert a scoped enumeration to its "
+                   "underlying type")
+              << ReplacementFunction;
+
+  // In Warn mode an imprecise cast is diagnosed without a fix-it
----------------
vbvictor wrote:

Same as above

https://github.com/llvm/llvm-project/pull/210459