RedundantLambdaParameterListCheck.cpp

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//===----------------------------------------------------------------------===//
//
// 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 "RedundantLambdaParameterListCheck.h"
#include "../utils/LexerUtils.h"
 
using namespace clang::ast_matchers;
 
namespace clang::tidy::readability {
 
namespace {
 
AST_MATCHER(LambdaExpr, hasRedundantParens) {
  return Node.hasExplicitParameters() &&
         Node.getCallOperator()->getNumParams() == 0 &&
         !Node.getCallOperator()->getTrailingRequiresClause();
}
 
} // namespace
 
void RedundantLambdaParameterListCheck::registerMatchers(MatchFinder *Finder) {
  Finder->addMatcher(lambdaExpr(hasRedundantParens()).bind("lambda"), this);
}
 
void RedundantLambdaParameterListCheck::check(
    const MatchFinder::MatchResult &Result) {
  const auto *Lambda = Result.Nodes.getNodeAs<LambdaExpr>("lambda");
 
  const LangOptions &LangOpts = getLangOpts();
 
  const FunctionTypeLoc FTL = Lambda->getCallOperator()->getFunctionTypeLoc();
  const SourceLocation LParenLoc = FTL.getLParenLoc();
  const SourceLocation RParenLoc = FTL.getRParenLoc();
 
  if (LParenLoc.isInvalid() || RParenLoc.isInvalid())
    return;
 
  // Ensure parens are truly empty (reject "(void)")
  const std::optional<Token> FirstInParens =
      utils::lexer::findNextTokenSkippingComments(
          LParenLoc, *Result.SourceManager, LangOpts);
 
  if (!FirstInParens || FirstInParens->getLocation() != RParenLoc)
    return;
 
  const std::optional<Token> NextAfterParenTok =
      utils::lexer::findNextTokenSkippingComments(
          RParenLoc, *Result.SourceManager, LangOpts);
 
  if (!NextAfterParenTok || NextAfterParenTok->is(tok::l_square))
    return;
 
  if (!LangOpts.CPlusPlus23 && NextAfterParenTok->isNot(tok::l_brace))
    return;
 
  diag(LParenLoc, "redundant empty parameter list in lambda expression")
      << FixItHint::CreateRemoval(LParenLoc)
      << FixItHint::CreateRemoval(RParenLoc);
}
 
} // namespace clang::tidy::readability