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//===--- ContainerSizeEmptyCheck.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 "ContainerSizeEmptyCheck.h"
#include "../utils/ASTUtils.h"
#include "../utils/Matchers.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 {
namespace tidy {
namespace readability {
using utils::IsBinaryOrTernary;
ContainerSizeEmptyCheck::ContainerSizeEmptyCheck(StringRef Name,
ClangTidyContext *Context)
: ClangTidyCheck(Name, Context) {}
void ContainerSizeEmptyCheck::registerMatchers(MatchFinder *Finder) {
// Only register the matchers for C++; the functionality currently does not
// provide any benefit to other languages, despite being benign.
if (!getLangOpts().CPlusPlus)
return;
const auto ValidContainer = qualType(hasUnqualifiedDesugaredType(
recordType(hasDeclaration(cxxRecordDecl(isSameOrDerivedFrom(
namedDecl(
has(cxxMethodDecl(
isConst(), parameterCountIs(0), isPublic(),
hasName("size"),
returns(qualType(isInteger(), unless(booleanType()))))
.bind("size")),
has(cxxMethodDecl(isConst(), parameterCountIs(0), isPublic(),
hasName("empty"), returns(booleanType()))
.bind("empty")))
.bind("container")))))));
const auto WrongUse = anyOf(
hasParent(binaryOperator(
matchers::isComparisonOperator(),
hasEitherOperand(ignoringImpCasts(anyOf(
integerLiteral(equals(1)), integerLiteral(equals(0))))))
.bind("SizeBinaryOp")),
hasParent(implicitCastExpr(
hasImplicitDestinationType(booleanType()),
anyOf(
hasParent(unaryOperator(hasOperatorName("!")).bind("NegOnSize")),
anything()))),
hasParent(explicitCastExpr(hasDestinationType(booleanType()))));
Finder->addMatcher(
cxxMemberCallExpr(on(expr(anyOf(hasType(ValidContainer),
hasType(pointsTo(ValidContainer)),
hasType(references(ValidContainer))))),
callee(cxxMethodDecl(hasName("size"))), WrongUse,
unless(hasAncestor(cxxMethodDecl(
ofClass(equalsBoundNode("container"))))))
.bind("SizeCallExpr"),
this);
// Empty constructor matcher.
const auto DefaultConstructor = cxxConstructExpr(
hasDeclaration(cxxConstructorDecl(isDefaultConstructor())));
// Comparison to empty string or empty constructor.
const auto WrongComparend = anyOf(
ignoringImpCasts(stringLiteral(hasSize(0))),
ignoringImpCasts(cxxBindTemporaryExpr(has(DefaultConstructor))),
ignoringImplicit(DefaultConstructor),
cxxConstructExpr(
hasDeclaration(cxxConstructorDecl(isCopyConstructor())),
has(expr(ignoringImpCasts(DefaultConstructor)))),
cxxConstructExpr(
hasDeclaration(cxxConstructorDecl(isMoveConstructor())),
has(expr(ignoringImpCasts(DefaultConstructor)))));
// Match the object being compared.
const auto STLArg =
anyOf(unaryOperator(
hasOperatorName("*"),
hasUnaryOperand(
expr(hasType(pointsTo(ValidContainer))).bind("Pointee"))),
expr(hasType(ValidContainer)).bind("STLObject"));
Finder->addMatcher(
cxxOperatorCallExpr(
anyOf(hasOverloadedOperatorName("=="),
hasOverloadedOperatorName("!=")),
anyOf(allOf(hasArgument(0, WrongComparend), hasArgument(1, STLArg)),
allOf(hasArgument(0, STLArg), hasArgument(1, WrongComparend))),
unless(hasAncestor(
cxxMethodDecl(ofClass(equalsBoundNode("container"))))))
.bind("BinCmp"),
this);
}
void ContainerSizeEmptyCheck::check(const MatchFinder::MatchResult &Result) {
const auto *MemberCall =
Result.Nodes.getNodeAs<CXXMemberCallExpr>("SizeCallExpr");
const auto *BinCmp = Result.Nodes.getNodeAs<CXXOperatorCallExpr>("BinCmp");
const auto *BinaryOp = Result.Nodes.getNodeAs<BinaryOperator>("SizeBinaryOp");
const auto *Pointee = Result.Nodes.getNodeAs<Expr>("Pointee");
const auto *E =
MemberCall
? MemberCall->getImplicitObjectArgument()
: (Pointee ? Pointee : Result.Nodes.getNodeAs<Expr>("STLObject"));
FixItHint Hint;
std::string ReplacementText =
Lexer::getSourceText(CharSourceRange::getTokenRange(E->getSourceRange()),
*Result.SourceManager, getLangOpts());
if (BinCmp && IsBinaryOrTernary(E)) {
// Not just a DeclRefExpr, so parenthesize to be on the safe side.
ReplacementText = "(" + ReplacementText + ")";
}
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 (BinaryOp) { // Determine the correct transformation.
bool Negation = false;
const bool ContainerIsLHS =
!llvm::isa<IntegerLiteral>(BinaryOp->getLHS()->IgnoreImpCasts());
const auto OpCode = BinaryOp->getOpcode();
uint64_t Value = 0;
if (ContainerIsLHS) {
if (const auto *Literal = llvm::dyn_cast<IntegerLiteral>(
BinaryOp->getRHS()->IgnoreImpCasts()))
Value = Literal->getValue().getLimitedValue();
else
return;
} else {
Value =
llvm::dyn_cast<IntegerLiteral>(BinaryOp->getLHS()->IgnoreImpCasts())
->getValue()
.getLimitedValue();
}
// Constant that is not handled.
if (Value > 1)
return;
if (Value == 1 && (OpCode == BinaryOperatorKind::BO_EQ ||
OpCode == BinaryOperatorKind::BO_NE))
return;
// Always true, no warnings for that.
if ((OpCode == BinaryOperatorKind::BO_GE && Value == 0 && ContainerIsLHS) ||
(OpCode == BinaryOperatorKind::BO_LE && Value == 0 && !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;
}
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);
}
if (MemberCall) {
diag(MemberCall->getBeginLoc(),
"the 'empty' method should be used to check "
"for emptiness instead of 'size'")
<< Hint;
} else {
diag(BinCmp->getBeginLoc(),
"the 'empty' method should be used to check "
"for emptiness instead of comparing to an empty object")
<< Hint;
}
const auto *Container = Result.Nodes.getNodeAs<NamedDecl>("container");
if (const auto *CTS = dyn_cast<ClassTemplateSpecializationDecl>(Container)) {
// The definition of the empty() method is the same for all implicit
// instantiations. In order to avoid duplicate or inconsistent warnings
// (depending on how deduplication is done), we use the same class name
// for all implicit instantiations of a template.
if (CTS->getSpecializationKind() == TSK_ImplicitInstantiation)
Container = CTS->getSpecializedTemplate();
}
const auto *Empty = Result.Nodes.getNodeAs<FunctionDecl>("empty");
diag(Empty->getLocation(), "method %0::empty() defined here",
DiagnosticIDs::Note)
<< Container;
}
} // namespace readability
} // namespace tidy
} // namespace clang
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