StringCompareCheck.cpp

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//===-- StringCompareCheck.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 "StringCompareCheck.h"
#include "../utils/FixItHintUtils.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/Tooling/FixIt.h"
 
using namespace clang::ast_matchers;
 
namespace clang::tidy::readability {
 
static const StringRef CompareMessage = "do not use 'compare' to test equality "
                                        "of strings; use the string equality "
                                        "operator instead";
 
void StringCompareCheck::registerMatchers(MatchFinder *Finder) {
  const auto StrCompare = cxxMemberCallExpr(
      callee(cxxMethodDecl(hasName("compare"),
                           ofClass(classTemplateSpecializationDecl(
                               hasName("::std::basic_string"))))),
      hasArgument(0, expr().bind("str2")), argumentCountIs(1),
      callee(memberExpr().bind("str1")));
 
  // First and second case: cast str.compare(str) to boolean.
  Finder->addMatcher(
      traverse(TK_AsIs,
               implicitCastExpr(hasImplicitDestinationType(booleanType()),
                                has(StrCompare))
                   .bind("match1")),
      this);
 
  // Third and fourth case: str.compare(str) == 0 and str.compare(str) != 0.
  Finder->addMatcher(
      binaryOperator(hasAnyOperatorName("==", "!="),
                     hasOperands(StrCompare.bind("compare"),
                                 integerLiteral(equals(0)).bind("zero")))
          .bind("match2"),
      this);
}
 
void StringCompareCheck::check(const MatchFinder::MatchResult &Result) {
  if (const auto *Matched = Result.Nodes.getNodeAs<Stmt>("match1")) {
    diag(Matched->getBeginLoc(), CompareMessage);
    return;
  }
 
  if (const auto *Matched = Result.Nodes.getNodeAs<Stmt>("match2")) {
    const ASTContext &Ctx = *Result.Context;
 
    if (const auto *Zero = Result.Nodes.getNodeAs<Stmt>("zero")) {
      const auto *Str1 = Result.Nodes.getNodeAs<MemberExpr>("str1");
      const auto *Str2 = Result.Nodes.getNodeAs<Stmt>("str2");
      const auto *Compare = Result.Nodes.getNodeAs<Stmt>("compare");
 
      auto Diag = diag(Matched->getBeginLoc(), CompareMessage);
 
      if (Str1->isArrow())
        Diag << FixItHint::CreateInsertion(Str1->getBeginLoc(), "*");
 
      Diag << tooling::fixit::createReplacement(*Zero, *Str2, Ctx)
           << tooling::fixit::createReplacement(*Compare, *Str1->getBase(),
                                                Ctx);
    }
  }
 
  // FIXME: Add fixit to fix the code for case one and two (match1).
}
 
} // namespace clang::tidy::readability