clang-tools-extra/clang-tidy/modernize/UseOverrideCheck.cpp

//===----------------------------------------------------------------------===//
//
// 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 "UseOverrideCheck.h"
#include "../utils/LexerUtils.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/Lex/Lexer.h"

using namespace clang::ast_matchers;

namespace clang::tidy::modernize {

UseOverrideCheck::UseOverrideCheck(StringRef Name, ClangTidyContext *Context)
    : ClangTidyCheck(Name, Context),
      IgnoreDestructors(Options.get("IgnoreDestructors", false)),
      IgnoreTemplateInstantiations(
          Options.get("IgnoreTemplateInstantiations", false)),
      AllowOverrideAndFinal(Options.get("AllowOverrideAndFinal", false)),
      OverrideSpelling(Options.get("OverrideSpelling", "override")),
      FinalSpelling(Options.get("FinalSpelling", "final")) {}

void UseOverrideCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
  Options.store(Opts, "IgnoreDestructors", IgnoreDestructors);
  Options.store(Opts, "IgnoreTemplateInstantiations",
                IgnoreTemplateInstantiations);
  Options.store(Opts, "AllowOverrideAndFinal", AllowOverrideAndFinal);
  Options.store(Opts, "OverrideSpelling", OverrideSpelling);
  Options.store(Opts, "FinalSpelling", FinalSpelling);
}

void UseOverrideCheck::registerMatchers(MatchFinder *Finder) {
  auto IgnoreDestructorMatcher =
      IgnoreDestructors ? cxxMethodDecl(unless(cxxDestructorDecl()))
                        : cxxMethodDecl();
  auto IgnoreTemplateInstantiationsMatcher =
      IgnoreTemplateInstantiations
          ? cxxMethodDecl(unless(ast_matchers::isTemplateInstantiation()))
          : cxxMethodDecl();
  Finder->addMatcher(cxxMethodDecl(isOverride(),
                                   IgnoreTemplateInstantiationsMatcher,
                                   IgnoreDestructorMatcher)
                         .bind("method"),
                     this);
}

// Re-lex the tokens to get precise locations to insert 'override' and remove
// 'virtual'.
static SmallVector<Token, 16>
parseTokens(CharSourceRange Range, const MatchFinder::MatchResult &Result) {
  const SourceManager &Sources = *Result.SourceManager;
  const std::pair<FileID, unsigned> LocInfo =
      Sources.getDecomposedLoc(Range.getBegin());
  const StringRef File = Sources.getBufferData(LocInfo.first);
  const char *TokenBegin = File.data() + LocInfo.second;
  Lexer RawLexer(Sources.getLocForStartOfFile(LocInfo.first),
                 Result.Context->getLangOpts(), File.begin(), TokenBegin,
                 File.end());
  SmallVector<Token, 16> Tokens;
  Token Tok;
  int NestedParens = 0;
  while (!RawLexer.LexFromRawLexer(Tok)) {
    if ((Tok.is(tok::semi) || Tok.is(tok::l_brace)) && NestedParens == 0)
      break;
    if (Sources.isBeforeInTranslationUnit(Range.getEnd(), Tok.getLocation()))
      break;
    if (Tok.is(tok::l_paren))
      ++NestedParens;
    else if (Tok.is(tok::r_paren))
      --NestedParens;
    if (Tok.is(tok::raw_identifier)) {
      IdentifierInfo &Info = Result.Context->Idents.get(StringRef(
          Sources.getCharacterData(Tok.getLocation()), Tok.getLength()));
      Tok.setIdentifierInfo(&Info);
      Tok.setKind(Info.getTokenID());
    }
    Tokens.push_back(Tok);
  }
  return Tokens;
}

void UseOverrideCheck::check(const MatchFinder::MatchResult &Result) {
  const auto *Method = Result.Nodes.getNodeAs<FunctionDecl>("method");
  const SourceManager &Sources = *Result.SourceManager;

  ASTContext &Context = *Result.Context;

  assert(Method != nullptr);
  if (Method->getInstantiatedFromMemberFunction() != nullptr)
    Method = Method->getInstantiatedFromMemberFunction();

  if (Method->isImplicit() || Method->getLocation().isMacroID() ||
      Method->isOutOfLine())
    return;

  const bool HasVirtual = Method->isVirtualAsWritten();
  const bool HasOverride = Method->getAttr<OverrideAttr>();
  const bool HasFinal = Method->getAttr<FinalAttr>();

  const bool OnlyVirtualSpecified = HasVirtual && !HasOverride && !HasFinal;
  const unsigned KeywordCount = HasVirtual + HasOverride + HasFinal;

  if ((!OnlyVirtualSpecified && KeywordCount == 1) ||
      (!HasVirtual && HasOverride && HasFinal && AllowOverrideAndFinal))
    return; // Nothing to do.

  std::string Message;
  if (OnlyVirtualSpecified) {
    Message = "prefer using '%0' or (rarely) '%1' instead of 'virtual'";
  } else if (KeywordCount == 0) {
    Message = "annotate this function with '%0' or (rarely) '%1'";
  } else {
    const StringRef Redundant =
        HasVirtual ? (HasOverride && HasFinal && !AllowOverrideAndFinal
                          ? "'virtual' and '%0' are"
                          : "'virtual' is")
                   : "'%0' is";
    const StringRef Correct = HasFinal ? "'%1'" : "'%0'";

    Message = (llvm::Twine(Redundant) +
               " redundant since the function is already declared " + Correct)
                  .str();
  }

  auto Diag = diag(Method->getLocation(), Message)
              << OverrideSpelling << FinalSpelling;

  const CharSourceRange FileRange = Lexer::makeFileCharRange(
      CharSourceRange::getTokenRange(Method->getSourceRange()), Sources,
      getLangOpts());

  if (!FileRange.isValid())
    return;

  // FIXME: Instead of re-lexing and looking for the 'virtual' token,
  // store the location of 'virtual' in each FunctionDecl.
  SmallVector<Token, 16> Tokens = parseTokens(FileRange, Result);

  // Add 'override' on inline declarations that don't already have it.
  if (!HasFinal && !HasOverride) {
    // If the override macro has been specified just ensure it exists,
    // if not don't apply a fixit but keep the warning.
    if (OverrideSpelling != "override" &&
        !Context.Idents.get(OverrideSpelling).hasMacroDefinition())
      return;

    Diag << FixItHint::CreateInsertion(
        Lexer::getLocForEndOfToken(
            Method->getTypeSourceInfo()->getTypeLoc().getEndLoc(), 0, Sources,
            getLangOpts()),
        (" " + OverrideSpelling).str());
  }

  if (HasFinal && HasOverride && !AllowOverrideAndFinal)
    Diag << FixItHint::CreateRemoval(
        Method->getAttr<OverrideAttr>()->getLocation());

  if (HasVirtual) {
    for (const Token Tok : Tokens) {
      if (Tok.is(tok::kw_virtual)) {
        std::optional<Token> NextToken =
            utils::lexer::findNextTokenIncludingComments(
                Tok.getEndLoc(), Sources, getLangOpts());
        if (NextToken.has_value()) {
          Diag << FixItHint::CreateRemoval(CharSourceRange::getCharRange(
              Tok.getLocation(), NextToken->getLocation()));
          break;
        }
      }
    }
  }
}

} // namespace clang::tidy::modernize