ContainerSizeEmptyCheck.cpp

Go to the documentation of this file.

//===----------------------------------------------------------------------===//
//
// 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 "ContainerSizeEmptyCheck.h"
#include "../utils/ASTUtils.h"
#include "../utils/Matchers.h"
#include "../utils/OptionsUtils.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchers.h"
#include "clang/Lex/Lexer.h"
#include "llvm/ADT/StringRef.h"
 
using namespace clang::ast_matchers;
 
namespace clang::tidy::readability {
 
namespace {
 
AST_POLYMORPHIC_MATCHER_P2(hasAnyArgumentWithParam,
                           AST_POLYMORPHIC_SUPPORTED_TYPES(CallExpr,
                                                           CXXConstructExpr),
                           ast_matchers::internal::Matcher<Expr>, ArgMatcher,
                           ast_matchers::internal::Matcher<ParmVarDecl>,
                           ParamMatcher) {
  ast_matchers::internal::BoundNodesTreeBuilder Result;
  // The first argument of an overloaded member operator is the implicit object
  // argument of the method which should not be matched against a parameter, so
  // we skip over it here.
  ast_matchers::internal::BoundNodesTreeBuilder Matches;
  unsigned ArgIndex = cxxOperatorCallExpr(callee(cxxMethodDecl()))
                              .matches(Node, Finder, &Matches)
                          ? 1
                          : 0;
  int ParamIndex = 0;
  for (; ArgIndex < Node.getNumArgs(); ++ArgIndex) {
    ast_matchers::internal::BoundNodesTreeBuilder ArgMatches(*Builder);
    if (ArgMatcher.matches(*(Node.getArg(ArgIndex)->IgnoreParenCasts()), Finder,
                           &ArgMatches)) {
      ast_matchers::internal::BoundNodesTreeBuilder ParamMatches(ArgMatches);
      if (expr(anyOf(cxxConstructExpr(hasDeclaration(cxxConstructorDecl(
                         hasParameter(ParamIndex, ParamMatcher)))),
                     callExpr(callee(functionDecl(
                         hasParameter(ParamIndex, ParamMatcher))))))
              .matches(Node, Finder, &ParamMatches)) {
        Result.addMatch(ParamMatches);
        *Builder = std::move(Result);
        return true;
      }
    }
    ++ParamIndex;
  }
  return false;
}
 
AST_MATCHER(Expr, usedInBooleanContext) {
  const char *ExprName = "__booleanContextExpr";
  auto Result =
      expr(expr().bind(ExprName),
           anyOf(hasParent(
                     mapAnyOf(varDecl, fieldDecl).with(hasType(booleanType()))),
                 hasParent(cxxConstructorDecl(
                     hasAnyConstructorInitializer(cxxCtorInitializer(
                         withInitializer(expr(equalsBoundNode(ExprName))),
                         forField(hasType(booleanType())))))),
                 hasParent(stmt(anyOf(
                     explicitCastExpr(hasDestinationType(booleanType())),
                     mapAnyOf(ifStmt, doStmt, whileStmt, forStmt,
                              conditionalOperator)
                         .with(hasCondition(expr(equalsBoundNode(ExprName)))),
                     parenListExpr(hasParent(varDecl(hasType(booleanType())))),
                     parenExpr(hasParent(
                         explicitCastExpr(hasDestinationType(booleanType())))),
                     returnStmt(forFunction(returns(booleanType()))),
                     cxxUnresolvedConstructExpr(hasType(booleanType())),
                     invocation(hasAnyArgumentWithParam(
                         expr(equalsBoundNode(ExprName)),
                         parmVarDecl(hasType(booleanType())))),
                     binaryOperator(hasAnyOperatorName("&&", "||")),
                     unaryOperator(hasOperatorName("!")).bind("NegOnSize"))))))
          .matches(Node, Finder, Builder);
  Builder->removeBindings(
      [ExprName](const ast_matchers::internal::BoundNodesMap &Nodes) {
        return Nodes.getNode(ExprName).getNodeKind().isNone();
      });
  return Result;
}
 
AST_MATCHER(QualType, isIntegralType) {
  return Node->isIntegralType(Finder->getASTContext());
}
 
AST_MATCHER_P(UserDefinedLiteral, hasLiteral,
              ast_matchers::internal::Matcher<Expr>, InnerMatcher) {
  const UserDefinedLiteral::LiteralOperatorKind LOK =
      Node.getLiteralOperatorKind();
  if (LOK == UserDefinedLiteral::LOK_Template ||
      LOK == UserDefinedLiteral::LOK_Raw)
    return false;
 
  if (const Expr *CookedLiteral = Node.getCookedLiteral())
    return InnerMatcher.matches(*CookedLiteral, Finder, Builder);
  return false;
}
 
AST_MATCHER_P(CXXMethodDecl, hasCanonicalDecl,
              ast_matchers::internal::Matcher<CXXMethodDecl>, InnerMatcher) {
  return InnerMatcher.matches(*Node.getCanonicalDecl(), Finder, Builder);
}
 
AST_POLYMORPHIC_MATCHER_P(
    matchMemberName,
    AST_POLYMORPHIC_SUPPORTED_TYPES(MemberExpr, CXXDependentScopeMemberExpr),
    std::string, MemberName) {
  if (const auto *E = dyn_cast<MemberExpr>(&Node)) {
    const IdentifierInfo *II = E->getMemberDecl()->getIdentifier();
    return II && II->getName() == MemberName;
  }
 
  if (const auto *E = dyn_cast<CXXDependentScopeMemberExpr>(&Node)) {
    const IdentifierInfo *II = E->getMember().getAsIdentifierInfo();
    return II && II->getName() == MemberName;
  }
 
  return false;
}
 
} // namespace
 
using utils::isBinaryOrTernary;
 
ContainerSizeEmptyCheck::ContainerSizeEmptyCheck(StringRef Name,
                                                 ClangTidyContext *Context)
    : ClangTidyCheck(Name, Context),
      ExcludedComparisonTypes(utils::options::parseStringList(
          Options.get("ExcludedComparisonTypes", "::std::array"))) {}
 
void ContainerSizeEmptyCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
  Options.store(Opts, "ExcludedComparisonTypes",
                utils::options::serializeStringList(ExcludedComparisonTypes));
}
 
void ContainerSizeEmptyCheck::registerMatchers(MatchFinder *Finder) {
  const auto ValidContainerRecord =
      cxxRecordDecl(
          isSameOrDerivedFrom(namedDecl(
              has(cxxMethodDecl(isConst(), parameterCountIs(0), isPublic(),
                                hasAnyName("size", "length"),
                                returns(qualType(isIntegralType(),
                                                 unless(booleanType()))))
                      .bind("size")),
              has(cxxMethodDecl(isConst(), parameterCountIs(0), isPublic(),
                                hasName("empty"), returns(booleanType()))
                      .bind("empty")))))
          .bind("ContainerDecl");
 
  const auto ValidContainerNonTemplateType =
      qualType(hasUnqualifiedDesugaredType(
          recordType(hasDeclaration(ValidContainerRecord))));
  const auto ValidContainerTemplateType = qualType(hasUnqualifiedDesugaredType(
      anyOf(templateSpecializationType(
                hasDeclaration(classTemplateDecl(has(ValidContainerRecord)))),
            injectedClassNameType(hasDeclaration(ValidContainerRecord)))));
 
  const auto ValidContainer = qualType(
      anyOf(ValidContainerNonTemplateType, ValidContainerTemplateType));
 
  const auto WrongUse =
      anyOf(hasParent(binaryOperator(
                          isComparisonOperator(),
                          hasEitherOperand(anyOf(integerLiteral(equals(1)),
                                                 integerLiteral(equals(0)))))
                          .bind("SizeBinaryOp")),
            usedInBooleanContext());
 
  const auto NotInEmptyMethodOfContainer = unless(
      forCallable(cxxMethodDecl(hasCanonicalDecl(equalsBoundNode("empty")))));
 
  Finder->addMatcher(
      cxxMemberCallExpr(
          argumentCountIs(0),
          on(expr(anyOf(hasType(ValidContainer),
                        hasType(pointsTo(ValidContainer)),
                        hasType(references(ValidContainer))))
                 .bind("MemberCallObject")),
          callee(
              cxxMethodDecl(hasAnyName("size", "length")).bind("SizeMethod")),
          WrongUse, NotInEmptyMethodOfContainer)
          .bind("SizeCallExpr"),
      this);
 
  Finder->addMatcher(
      callExpr(
          argumentCountIs(0),
          has(mapAnyOf(memberExpr, cxxDependentScopeMemberExpr)
                  .with(
                      hasObjectExpression(
                          expr(anyOf(hasType(ValidContainer),
                                     hasType(pointsTo(ValidContainer)),
                                     hasType(references(ValidContainer))))
                              .bind("MemberCallObject")),
                      anyOf(matchMemberName("size"), matchMemberName("length")))
                  .bind("MemberExpr")),
          WrongUse, NotInEmptyMethodOfContainer)
          .bind("SizeCallExpr"),
      this);
 
  // Comparison to empty string or empty constructor.
  const auto WrongComparend =
      anyOf(stringLiteral(hasSize(0)),
            userDefinedLiteral(hasLiteral(stringLiteral(hasSize(0)))),
            cxxConstructExpr(argumentCountIs(0)),
            cxxUnresolvedConstructExpr(argumentCountIs(0)));
  // Match the object being compared.
  const auto STLArg =
      anyOf(unaryOperator(
                hasOperatorName("*"),
                hasUnaryOperand(
                    expr(hasType(pointsTo(ValidContainer))).bind("Pointee"))),
            expr(hasType(ValidContainer)).bind("STLObject"));
 
  const auto ExcludedComparisonTypesMatcher = qualType(
      anyOf(hasDeclaration(cxxRecordDecl(matchers::matchesAnyListedRegexName(
                                             ExcludedComparisonTypes))
                               .bind("excluded")),
            hasCanonicalType(hasDeclaration(
                cxxRecordDecl(matchers::matchesAnyListedRegexName(
                                  ExcludedComparisonTypes))
                    .bind("excluded")))));
  const auto SameExcludedComparisonTypesMatcher =
      qualType(anyOf(hasDeclaration(cxxRecordDecl(equalsBoundNode("excluded"))),
                     hasCanonicalType(hasDeclaration(
                         cxxRecordDecl(equalsBoundNode("excluded"))))));
 
  Finder->addMatcher(
      binaryOperation(
          hasAnyOperatorName("==", "!="), hasOperands(WrongComparend, STLArg),
          unless(hasEitherOperand(cxxConstructExpr(
              argumentCountIs(0),
              unless(hasType(qualType(hasCanonicalType(hasDeclaration(
                  // 'equalsBoundNode' needs the 'ContainerDecl' binding
                  // from 'STLArg' to already exist, so this constraint must
                  // appear after 'hasOperands' matcher
                  namedDecl(equalsBoundNode("ContainerDecl")))))))))),
          unless(allOf(hasLHS(hasType(ExcludedComparisonTypesMatcher)),
                       hasRHS(hasType(SameExcludedComparisonTypesMatcher)))),
          NotInEmptyMethodOfContainer)
          .bind("BinCmp"),
      this);
}
 
void ContainerSizeEmptyCheck::check(const MatchFinder::MatchResult &Result) {
  const auto *MemberCall = Result.Nodes.getNodeAs<Expr>("SizeCallExpr");
  const auto *MemberCallObject =
      Result.Nodes.getNodeAs<Expr>("MemberCallObject");
  const auto *BinCmp = Result.Nodes.getNodeAs<CXXOperatorCallExpr>("BinCmp");
  const auto *BinCmpTempl = Result.Nodes.getNodeAs<BinaryOperator>("BinCmp");
  const auto *BinCmpRewritten =
      Result.Nodes.getNodeAs<CXXRewrittenBinaryOperator>("BinCmp");
  const auto *BinaryOp = Result.Nodes.getNodeAs<BinaryOperator>("SizeBinaryOp");
  const auto *Pointee = Result.Nodes.getNodeAs<Expr>("Pointee");
  const auto *E =
      MemberCallObject
          ? MemberCallObject
          : (Pointee ? Pointee : Result.Nodes.getNodeAs<Expr>("STLObject"));
  FixItHint Hint;
  std::string ReplacementText =
      E->isImplicitCXXThis()
          ? ""
          : std::string(Lexer::getSourceText(
                CharSourceRange::getTokenRange(E->getSourceRange()),
                *Result.SourceManager, getLangOpts()));
  const auto *OpCallExpr = dyn_cast<CXXOperatorCallExpr>(E);
  if (isBinaryOrTernary(E) || isa<UnaryOperator>(E) ||
      (OpCallExpr && (OpCallExpr->getOperator() == OO_Star))) {
    ReplacementText = "(" + ReplacementText + ")";
  }
  if (OpCallExpr &&
      OpCallExpr->getOperator() == OverloadedOperatorKind::OO_Arrow) {
    // This can happen if the object is a smart pointer. Don't add anything
    // because a '->' is already there (PR#51776), just call the method.
    ReplacementText += "empty()";
  } else if (E->isImplicitCXXThis()) {
    ReplacementText += "empty()";
  } else if (E->getType()->isPointerType()) {
    ReplacementText += "->empty()";
  } else {
    ReplacementText += ".empty()";
  }
 
  if (BinCmp) {
    if (BinCmp->getOperator() == OO_ExclaimEqual)
      ReplacementText = "!" + ReplacementText;
    Hint =
        FixItHint::CreateReplacement(BinCmp->getSourceRange(), ReplacementText);
  } else if (BinCmpTempl) {
    if (BinCmpTempl->getOpcode() == BinaryOperatorKind::BO_NE)
      ReplacementText = "!" + ReplacementText;
    Hint = FixItHint::CreateReplacement(BinCmpTempl->getSourceRange(),
                                        ReplacementText);
  } else if (BinCmpRewritten) {
    if (BinCmpRewritten->getOpcode() == BinaryOperatorKind::BO_NE)
      ReplacementText = "!" + ReplacementText;
    Hint = FixItHint::CreateReplacement(BinCmpRewritten->getSourceRange(),
                                        ReplacementText);
  } else if (BinaryOp) { // Determine the correct transformation.
    const auto *LiteralLHS =
        dyn_cast<IntegerLiteral>(BinaryOp->getLHS()->IgnoreImpCasts());
    const auto *LiteralRHS =
        dyn_cast<IntegerLiteral>(BinaryOp->getRHS()->IgnoreImpCasts());
    const bool ContainerIsLHS = !LiteralLHS;
 
    uint64_t Value = 0;
    if (LiteralLHS)
      Value = LiteralLHS->getValue().getLimitedValue();
    else if (LiteralRHS)
      Value = LiteralRHS->getValue().getLimitedValue();
    else
      return;
 
    bool Negation = false;
    const auto OpCode = BinaryOp->getOpcode();
 
    // Constant that is not handled.
    if (Value > 1)
      return;
 
    if (Value == 1 && (OpCode == BinaryOperatorKind::BO_EQ ||
                       OpCode == BinaryOperatorKind::BO_NE))
      return;
 
    // Always true/false, no warnings for that.
    if (Value == 0) {
      if ((OpCode == BinaryOperatorKind::BO_GT && !ContainerIsLHS) ||
          (OpCode == BinaryOperatorKind::BO_LT && ContainerIsLHS) ||
          (OpCode == BinaryOperatorKind::BO_LE && !ContainerIsLHS) ||
          (OpCode == BinaryOperatorKind::BO_GE && ContainerIsLHS))
        return;
    }
 
    // Do not warn for size > 1, 1 < size, size <= 1, 1 >= size.
    if (Value == 1) {
      if ((OpCode == BinaryOperatorKind::BO_GT && ContainerIsLHS) ||
          (OpCode == BinaryOperatorKind::BO_LT && !ContainerIsLHS))
        return;
      if ((OpCode == BinaryOperatorKind::BO_LE && ContainerIsLHS) ||
          (OpCode == BinaryOperatorKind::BO_GE && !ContainerIsLHS))
        return;
    }
 
    // Do not warn for size < 1, 1 > size, size <= 0, 0 >= size for non signed
    // types
    if ((OpCode == BinaryOperatorKind::BO_GT && Value == 1 &&
         !ContainerIsLHS) ||
        (OpCode == BinaryOperatorKind::BO_LT && Value == 1 && ContainerIsLHS) ||
        (OpCode == BinaryOperatorKind::BO_GE && Value == 0 &&
         !ContainerIsLHS) ||
        (OpCode == BinaryOperatorKind::BO_LE && Value == 0 && ContainerIsLHS)) {
      const Expr *Container = ContainerIsLHS
                                  ? BinaryOp->getLHS()->IgnoreImpCasts()
                                  : BinaryOp->getRHS()->IgnoreImpCasts();
      if (Container->getType()
              .getCanonicalType()
              .getNonReferenceType()
              ->isSignedIntegerType())
        return;
    }
 
    if (OpCode == BinaryOperatorKind::BO_NE && Value == 0)
      Negation = true;
 
    if ((OpCode == BinaryOperatorKind::BO_GT ||
         OpCode == BinaryOperatorKind::BO_GE) &&
        ContainerIsLHS)
      Negation = true;
 
    if ((OpCode == BinaryOperatorKind::BO_LT ||
         OpCode == BinaryOperatorKind::BO_LE) &&
        !ContainerIsLHS)
      Negation = true;
 
    if (Negation)
      ReplacementText = "!" + ReplacementText;
    Hint = FixItHint::CreateReplacement(BinaryOp->getSourceRange(),
                                        ReplacementText);
 
  } else {
    // If there is a conversion above the size call to bool, it is safe to just
    // replace size with empty.
    if (const auto *UnaryOp =
            Result.Nodes.getNodeAs<UnaryOperator>("NegOnSize"))
      Hint = FixItHint::CreateReplacement(UnaryOp->getSourceRange(),
                                          ReplacementText);
    else
      Hint = FixItHint::CreateReplacement(MemberCall->getSourceRange(),
                                          "!" + ReplacementText);
  }
 
  auto WarnLoc = MemberCall ? MemberCall->getBeginLoc() : SourceLocation{};
 
  if (WarnLoc.isValid()) {
    auto Diag = diag(WarnLoc, "the 'empty' method should be used to check "
                              "for emptiness instead of %0");
    if (const auto *SizeMethod =
            Result.Nodes.getNodeAs<NamedDecl>("SizeMethod"))
      Diag << SizeMethod;
    else if (const auto *DependentExpr =
                 Result.Nodes.getNodeAs<CXXDependentScopeMemberExpr>(
                     "MemberExpr"))
      Diag << DependentExpr->getMember();
    else if (const auto *ME = Result.Nodes.getNodeAs<MemberExpr>("MemberExpr"))
      Diag << ME->getMemberNameInfo().getName();
    else
      Diag << "unknown method";
    Diag << Hint;
  } else {
    WarnLoc = BinCmpTempl
                  ? BinCmpTempl->getBeginLoc()
                  : (BinCmp ? BinCmp->getBeginLoc()
                            : (BinCmpRewritten ? BinCmpRewritten->getBeginLoc()
                                               : SourceLocation{}));
    diag(WarnLoc, "the 'empty' method should be used to check "
                  "for emptiness instead of comparing to an empty object")
        << Hint;
  }
}
 
} // namespace clang::tidy::readability