llvm-project/clang-tools-extra/clang-tidy/modernize/UseDefaultCheck.cpp

289 lines
11 KiB
C++

//===--- UseDefaultCheck.cpp - clang-tidy----------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "UseDefaultCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/Lex/Lexer.h"
using namespace clang::ast_matchers;
namespace clang {
namespace tidy {
namespace modernize {
static const char SpecialFunction[] = "SpecialFunction";
/// \brief Finds all the named non-static fields of \p Record.
static std::set<const FieldDecl *>
getAllNamedFields(const CXXRecordDecl *Record) {
std::set<const FieldDecl *> Result;
for (const auto *Field : Record->fields()) {
// Static data members are not in this range.
if (Field->isUnnamedBitfield())
continue;
Result.insert(Field);
}
return Result;
}
/// \brief Returns the names of the direct bases of \p Record, both virtual and
/// non-virtual.
static std::set<const Type *> getAllDirectBases(const CXXRecordDecl *Record) {
std::set<const Type *> Result;
for (auto Base : Record->bases()) {
// CXXBaseSpecifier.
const auto *BaseType = Base.getTypeSourceInfo()->getType().getTypePtr();
Result.insert(BaseType);
}
return Result;
}
/// \brief Returns a matcher that matches member expressions where the base is
/// the variable declared as \p Var and the accessed member is the one declared
/// as \p Field.
internal::Matcher<Expr> accessToFieldInVar(const FieldDecl *Field,
const ValueDecl *Var) {
return ignoringImpCasts(
memberExpr(hasObjectExpression(declRefExpr(to(varDecl(equalsNode(Var))))),
member(fieldDecl(equalsNode(Field)))));
}
/// \brief Check that the given constructor has copy signature and that it
/// copy-initializes all its bases and members.
static bool isCopyConstructorAndCanBeDefaulted(ASTContext *Context,
const CXXConstructorDecl *Ctor) {
// An explicitly-defaulted constructor cannot have default arguments.
if (Ctor->getMinRequiredArguments() != 1)
return false;
const auto *Record = Ctor->getParent();
const auto *Param = Ctor->getParamDecl(0);
// Base classes and members that have to be copied.
auto BasesToInit = getAllDirectBases(Record);
auto FieldsToInit = getAllNamedFields(Record);
// Ensure that all the bases are copied.
for (const auto *Base : BasesToInit) {
// The initialization of a base class should be a call to a copy
// constructor of the base.
if (match(
cxxConstructorDecl(forEachConstructorInitializer(cxxCtorInitializer(
isBaseInitializer(),
withInitializer(cxxConstructExpr(allOf(
hasType(equalsNode(Base)),
hasDeclaration(cxxConstructorDecl(isCopyConstructor())),
argumentCountIs(1),
hasArgument(
0, declRefExpr(to(varDecl(equalsNode(Param))))))))))),
*Ctor, *Context)
.empty())
return false;
}
// Ensure that all the members are copied.
for (const auto *Field : FieldsToInit) {
auto AccessToFieldInParam = accessToFieldInVar(Field, Param);
// The initialization is a CXXConstructExpr for class types.
if (match(
cxxConstructorDecl(forEachConstructorInitializer(cxxCtorInitializer(
isMemberInitializer(), forField(equalsNode(Field)),
withInitializer(anyOf(
AccessToFieldInParam,
cxxConstructExpr(allOf(
hasDeclaration(cxxConstructorDecl(isCopyConstructor())),
argumentCountIs(1),
hasArgument(0, AccessToFieldInParam)))))))),
*Ctor, *Context)
.empty())
return false;
}
// Ensure that we don't do anything else, like initializing an indirect base.
return Ctor->getNumCtorInitializers() ==
BasesToInit.size() + FieldsToInit.size();
}
/// \brief Checks that the given method is an overloading of the assignment
/// operator, has copy signature, returns a reference to "*this" and copies
/// all its members and subobjects.
static bool isCopyAssignmentAndCanBeDefaulted(ASTContext *Context,
const CXXMethodDecl *Operator) {
const auto *Record = Operator->getParent();
const auto *Param = Operator->getParamDecl(0);
// Base classes and members that have to be copied.
auto BasesToInit = getAllDirectBases(Record);
auto FieldsToInit = getAllNamedFields(Record);
const auto *Compound = cast<CompoundStmt>(Operator->getBody());
// The assignment operator definition has to end with the following return
// statement:
// return *this;
if (Compound->body_empty() ||
match(returnStmt(has(ignoringParenImpCasts(unaryOperator(
hasOperatorName("*"), hasUnaryOperand(cxxThisExpr()))))),
*Compound->body_back(), *Context)
.empty())
return false;
// Ensure that all the bases are copied.
for (const auto *Base : BasesToInit) {
// Assignment operator of a base class:
// Base::operator=(Other);
//
// Clang translates this into:
// ((Base*)this)->operator=((Base)Other);
//
// So we are looking for a member call that fulfills:
if (match(compoundStmt(has(ignoringParenImpCasts(cxxMemberCallExpr(allOf(
// - The object is an implicit cast of 'this' to a pointer to
// a base class.
onImplicitObjectArgument(
implicitCastExpr(hasImplicitDestinationType(
pointsTo(type(equalsNode(Base)))),
hasSourceExpression(cxxThisExpr()))),
// - The called method is the operator=.
callee(cxxMethodDecl(isCopyAssignmentOperator())),
// - The argument is (an implicit cast to a Base of) the
// argument taken by "Operator".
argumentCountIs(1),
hasArgument(0,
declRefExpr(to(varDecl(equalsNode(Param)))))))))),
*Compound, *Context)
.empty())
return false;
}
// Ensure that all the members are copied.
for (const auto *Field : FieldsToInit) {
// The assignment of data members:
// Field = Other.Field;
// Is a BinaryOperator in non-class types, and a CXXOperatorCallExpr
// otherwise.
auto LHS = memberExpr(hasObjectExpression(cxxThisExpr()),
member(fieldDecl(equalsNode(Field))));
auto RHS = accessToFieldInVar(Field, Param);
if (match(
compoundStmt(has(ignoringParenImpCasts(stmt(anyOf(
binaryOperator(hasOperatorName("="), hasLHS(LHS), hasRHS(RHS)),
cxxOperatorCallExpr(hasOverloadedOperatorName("="),
argumentCountIs(2), hasArgument(0, LHS),
hasArgument(1, RHS))))))),
*Compound, *Context)
.empty())
return false;
}
// Ensure that we don't do anything else.
return Compound->size() == BasesToInit.size() + FieldsToInit.size() + 1;
}
/// \brief Returns false if the body has any non-whitespace character.
static bool bodyEmpty(const ASTContext *Context, const CompoundStmt *Body) {
bool Invalid = false;
StringRef Text = Lexer::getSourceText(
CharSourceRange::getCharRange(Body->getLBracLoc().getLocWithOffset(1),
Body->getRBracLoc()),
Context->getSourceManager(), Context->getLangOpts(), &Invalid);
return !Invalid && std::strspn(Text.data(), " \t\r\n") == Text.size();
}
void UseDefaultCheck::registerMatchers(MatchFinder *Finder) {
if (getLangOpts().CPlusPlus) {
// Destructor.
Finder->addMatcher(cxxDestructorDecl(isDefinition()).bind(SpecialFunction),
this);
Finder->addMatcher(
cxxConstructorDecl(
isDefinition(),
anyOf(
// Default constructor.
allOf(unless(hasAnyConstructorInitializer(isWritten())),
parameterCountIs(0)),
// Copy constructor.
allOf(isCopyConstructor(),
// Discard constructors that can be used as a copy
// constructor because all the other arguments have
// default values.
parameterCountIs(1))))
.bind(SpecialFunction),
this);
// Copy-assignment operator.
Finder->addMatcher(
cxxMethodDecl(isDefinition(), isCopyAssignmentOperator(),
// isCopyAssignmentOperator() allows the parameter to be
// passed by value, and in this case it cannot be
// defaulted.
hasParameter(0, hasType(lValueReferenceType())))
.bind(SpecialFunction),
this);
}
}
void UseDefaultCheck::check(const MatchFinder::MatchResult &Result) {
std::string SpecialFunctionName;
// Both CXXConstructorDecl and CXXDestructorDecl inherit from CXXMethodDecl.
const auto *SpecialFunctionDecl =
Result.Nodes.getNodeAs<CXXMethodDecl>(SpecialFunction);
// Discard explicitly deleted/defaulted special member functions and those
// that are not user-provided (automatically generated).
if (SpecialFunctionDecl->isDeleted() ||
SpecialFunctionDecl->isExplicitlyDefaulted() ||
SpecialFunctionDecl->isLateTemplateParsed() ||
SpecialFunctionDecl->isTemplateInstantiation() ||
!SpecialFunctionDecl->isUserProvided() || !SpecialFunctionDecl->hasBody())
return;
const auto *Body = dyn_cast<CompoundStmt>(SpecialFunctionDecl->getBody());
if (!Body)
return;
// If there are comments inside the body, don't do the change.
if (!SpecialFunctionDecl->isCopyAssignmentOperator() &&
!bodyEmpty(Result.Context, Body))
return;
std::vector<FixItHint> RemoveInitializers;
if (const auto *Ctor = dyn_cast<CXXConstructorDecl>(SpecialFunctionDecl)) {
if (Ctor->getNumParams() == 0) {
SpecialFunctionName = "default constructor";
} else {
if (!isCopyConstructorAndCanBeDefaulted(Result.Context, Ctor))
return;
SpecialFunctionName = "copy constructor";
// If there are constructor initializers, they must be removed.
for (const auto *Init : Ctor->inits()) {
RemoveInitializers.emplace_back(
FixItHint::CreateRemoval(Init->getSourceRange()));
}
}
} else if (isa<CXXDestructorDecl>(SpecialFunctionDecl)) {
SpecialFunctionName = "destructor";
} else {
if (!isCopyAssignmentAndCanBeDefaulted(Result.Context, SpecialFunctionDecl))
return;
SpecialFunctionName = "copy-assignment operator";
}
diag(SpecialFunctionDecl->getLocStart(),
"use '= default' to define a trivial " + SpecialFunctionName)
<< FixItHint::CreateReplacement(Body->getSourceRange(), "= default;")
<< RemoveInitializers;
}
} // namespace modernize
} // namespace tidy
} // namespace clang