clang-tools-extra/clang-tidy/readability/StringCompareCheck.cpp

   1 //===-- StringCompareCheck.cpp - clang-tidy--------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "StringCompareCheck.h"
  10 #include "../utils/FixItHintUtils.h"
  11 #include "clang/AST/ASTContext.h"
  12 #include "clang/ASTMatchers/ASTMatchFinder.h"
  13 #include "clang/Tooling/FixIt.h"
  14
  15 using namespace clang::ast_matchers;
  16
  17 namespace clang::tidy::readability {
  18
  19 static const StringRef CompareMessage = "do not use 'compare' to test equality "
  20                                         "of strings; use the string equality "
  21                                         "operator instead";
  22
  23 void StringCompareCheck::registerMatchers(MatchFinder *Finder) {
  24   const auto StrCompare = cxxMemberCallExpr(
  25       callee(cxxMethodDecl(hasName("compare"),
  26                            ofClass(classTemplateSpecializationDecl(
  27                                hasName("::std::basic_string"))))),
  28       hasArgument(0, expr().bind("str2")), argumentCountIs(1),
  29       callee(memberExpr().bind("str1")));
  30
  31   // First and second case: cast str.compare(str) to boolean.
  32   Finder->addMatcher(
  33       traverse(TK_AsIs,
  34                implicitCastExpr(hasImplicitDestinationType(booleanType()),
  35                                 has(StrCompare))
  36                    .bind("match1")),
  37       this);
  38
  39   // Third and fourth case: str.compare(str) == 0 and str.compare(str) != 0.
  40   Finder->addMatcher(
  41       binaryOperator(hasAnyOperatorName("==", "!="),
  42                      hasOperands(StrCompare.bind("compare"),
  43                                  integerLiteral(equals(0)).bind("zero")))
  44           .bind("match2"),
  45       this);
  46 }
  47
  48 void StringCompareCheck::check(const MatchFinder::MatchResult &Result) {
  49   if (const auto *Matched = Result.Nodes.getNodeAs<Stmt>("match1")) {
  50     diag(Matched->getBeginLoc(), CompareMessage);
  51     return;
  52   }
  53
  54   if (const auto *Matched = Result.Nodes.getNodeAs<Stmt>("match2")) {
  55     const ASTContext &Ctx = *Result.Context;
  56
  57     if (const auto *Zero = Result.Nodes.getNodeAs<Stmt>("zero")) {
  58       const auto *Str1 = Result.Nodes.getNodeAs<MemberExpr>("str1");
  59       const auto *Str2 = Result.Nodes.getNodeAs<Stmt>("str2");
  60       const auto *Compare = Result.Nodes.getNodeAs<Stmt>("compare");
  61
  62       auto Diag = diag(Matched->getBeginLoc(), CompareMessage);
  63
  64       if (Str1->isArrow())
  65         Diag << FixItHint::CreateInsertion(Str1->getBeginLoc(), "*");
  66
  67       Diag << tooling::fixit::createReplacement(*Zero, *Str2, Ctx)
  68            << tooling::fixit::createReplacement(*Compare, *Str1->getBase(),
  69                                                 Ctx);
  70     }
  71   }
  72
  73   // FIXME: Add fixit to fix the code for case one and two (match1).
  74 }
  75
  76 } // namespace clang::tidy::readability