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//===--- MoveConstArgCheck.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 "MoveConstArgCheck.h"
#include "clang/Lex/Lexer.h"
using namespace clang::ast_matchers;
namespace clang {
namespace tidy {
namespace performance {
static void ReplaceCallWithArg(const CallExpr *Call, DiagnosticBuilder &Diag,
const SourceManager &SM,
const LangOptions &LangOpts) {
const Expr *Arg = Call->getArg(0);
CharSourceRange BeforeArgumentsRange = Lexer::makeFileCharRange(
CharSourceRange::getCharRange(Call->getBeginLoc(), Arg->getBeginLoc()),
SM, LangOpts);
CharSourceRange AfterArgumentsRange = Lexer::makeFileCharRange(
CharSourceRange::getCharRange(Call->getEndLoc(),
Call->getEndLoc().getLocWithOffset(1)),
SM, LangOpts);
if (BeforeArgumentsRange.isValid() && AfterArgumentsRange.isValid()) {
Diag << FixItHint::CreateRemoval(BeforeArgumentsRange)
<< FixItHint::CreateRemoval(AfterArgumentsRange);
}
}
void MoveConstArgCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
Options.store(Opts, "CheckTriviallyCopyableMove", CheckTriviallyCopyableMove);
}
void MoveConstArgCheck::registerMatchers(MatchFinder *Finder) {
if (!getLangOpts().CPlusPlus)
return;
auto MoveCallMatcher =
callExpr(callee(functionDecl(hasName("::std::move"))), argumentCountIs(1),
unless(isInTemplateInstantiation()))
.bind("call-move");
Finder->addMatcher(MoveCallMatcher, this);
auto ConstParamMatcher = forEachArgumentWithParam(
MoveCallMatcher, parmVarDecl(hasType(references(isConstQualified()))));
Finder->addMatcher(callExpr(ConstParamMatcher).bind("receiving-expr"), this);
Finder->addMatcher(cxxConstructExpr(ConstParamMatcher).bind("receiving-expr"),
this);
}
void MoveConstArgCheck::check(const MatchFinder::MatchResult &Result) {
const auto *CallMove = Result.Nodes.getNodeAs<CallExpr>("call-move");
const auto *ReceivingExpr = Result.Nodes.getNodeAs<Expr>("receiving-expr");
const Expr *Arg = CallMove->getArg(0);
SourceManager &SM = Result.Context->getSourceManager();
CharSourceRange MoveRange =
CharSourceRange::getCharRange(CallMove->getSourceRange());
CharSourceRange FileMoveRange =
Lexer::makeFileCharRange(MoveRange, SM, getLangOpts());
if (!FileMoveRange.isValid())
return;
bool IsConstArg = Arg->getType().isConstQualified();
bool IsTriviallyCopyable =
Arg->getType().isTriviallyCopyableType(*Result.Context);
if (IsConstArg || IsTriviallyCopyable) {
if (const CXXRecordDecl *R = Arg->getType()->getAsCXXRecordDecl()) {
// According to [expr.prim.lambda]p3, "whether the closure type is
// trivially copyable" property can be changed by the implementation of
// the language, so we shouldn't rely on it when issuing diagnostics.
if (R->isLambda())
return;
// Don't warn when the type is not copyable.
for (const auto *Ctor : R->ctors()) {
if (Ctor->isCopyConstructor() && Ctor->isDeleted())
return;
}
}
if (!IsConstArg && IsTriviallyCopyable && !CheckTriviallyCopyableMove)
return;
bool IsVariable = isa<DeclRefExpr>(Arg);
const auto *Var =
IsVariable ? dyn_cast<DeclRefExpr>(Arg)->getDecl() : nullptr;
auto Diag = diag(FileMoveRange.getBegin(),
"std::move of the %select{|const }0"
"%select{expression|variable %4}1 "
"%select{|of the trivially-copyable type %5 }2"
"has no effect; remove std::move()"
"%select{| or make the variable non-const}3")
<< IsConstArg << IsVariable << IsTriviallyCopyable
<< (IsConstArg && IsVariable && !IsTriviallyCopyable) << Var
<< Arg->getType();
ReplaceCallWithArg(CallMove, Diag, SM, getLangOpts());
} else if (ReceivingExpr) {
auto Diag = diag(FileMoveRange.getBegin(),
"passing result of std::move() as a const reference "
"argument; no move will actually happen");
ReplaceCallWithArg(CallMove, Diag, SM, getLangOpts());
}
}
} // namespace performance
} // namespace tidy
} // namespace clang
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