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//===--- MoveForwardingReferenceCheck.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 "MoveForwardingReferenceCheck.h"
#include "clang/Lex/Lexer.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
using namespace clang::ast_matchers;
namespace clang::tidy::bugprone {
static void replaceMoveWithForward(const UnresolvedLookupExpr *Callee,
const ParmVarDecl *ParmVar,
const TemplateTypeParmDecl *TypeParmDecl,
DiagnosticBuilder &Diag,
const ASTContext &Context) {
const SourceManager &SM = Context.getSourceManager();
const LangOptions &LangOpts = Context.getLangOpts();
CharSourceRange CallRange =
Lexer::makeFileCharRange(CharSourceRange::getTokenRange(
Callee->getBeginLoc(), Callee->getEndLoc()),
SM, LangOpts);
if (CallRange.isValid()) {
const std::string TypeName =
(TypeParmDecl->getIdentifier() && !TypeParmDecl->isImplicit())
? TypeParmDecl->getName().str()
: (llvm::Twine("decltype(") + ParmVar->getName() + ")").str();
const std::string ForwardName =
(llvm::Twine("forward<") + TypeName + ">").str();
// Create a replacement only if we see a "standard" way of calling
// std::move(). This will hopefully prevent erroneous replacements if the
// code does unusual things (e.g. create an alias for std::move() in
// another namespace).
NestedNameSpecifier *NNS = Callee->getQualifier();
if (!NNS) {
// Called as "move" (i.e. presumably the code had a "using std::move;").
// We still conservatively put a "std::" in front of the forward because
// we don't know whether the code also had a "using std::forward;".
Diag << FixItHint::CreateReplacement(CallRange, "std::" + ForwardName);
} else if (const NamespaceDecl *Namespace = NNS->getAsNamespace()) {
if (Namespace->getName() == "std") {
if (!NNS->getPrefix()) {
// Called as "std::move".
Diag << FixItHint::CreateReplacement(CallRange,
"std::" + ForwardName);
} else if (NNS->getPrefix()->getKind() == NestedNameSpecifier::Global) {
// Called as "::std::move".
Diag << FixItHint::CreateReplacement(CallRange,
"::std::" + ForwardName);
}
}
}
}
}
void MoveForwardingReferenceCheck::registerMatchers(MatchFinder *Finder) {
// Matches a ParmVarDecl for a forwarding reference, i.e. a non-const rvalue
// reference of a function template parameter type.
auto ForwardingReferenceParmMatcher =
parmVarDecl(
hasType(qualType(rValueReferenceType(),
references(templateTypeParmType(hasDeclaration(
templateTypeParmDecl().bind("type-parm-decl")))),
unless(references(qualType(isConstQualified()))))))
.bind("parm-var");
Finder->addMatcher(
callExpr(callee(unresolvedLookupExpr(
hasAnyDeclaration(namedDecl(
hasUnderlyingDecl(hasName("::std::move")))))
.bind("lookup")),
argumentCountIs(1),
hasArgument(0, ignoringParenImpCasts(declRefExpr(
to(ForwardingReferenceParmMatcher)))))
.bind("call-move"),
this);
}
void MoveForwardingReferenceCheck::check(
const MatchFinder::MatchResult &Result) {
const auto *CallMove = Result.Nodes.getNodeAs<CallExpr>("call-move");
const auto *UnresolvedLookup =
Result.Nodes.getNodeAs<UnresolvedLookupExpr>("lookup");
const auto *ParmVar = Result.Nodes.getNodeAs<ParmVarDecl>("parm-var");
const auto *TypeParmDecl =
Result.Nodes.getNodeAs<TemplateTypeParmDecl>("type-parm-decl");
// Get the FunctionDecl and FunctionTemplateDecl containing the function
// parameter.
const auto *FuncForParam = dyn_cast<FunctionDecl>(ParmVar->getDeclContext());
if (!FuncForParam)
return;
const FunctionTemplateDecl *FuncTemplate =
FuncForParam->getDescribedFunctionTemplate();
if (!FuncTemplate)
return;
// Check that the template type parameter belongs to the same function
// template as the function parameter of that type. (This implies that type
// deduction will happen on the type.)
const TemplateParameterList *Params = FuncTemplate->getTemplateParameters();
if (!llvm::is_contained(*Params, TypeParmDecl))
return;
auto Diag = diag(CallMove->getExprLoc(),
"forwarding reference passed to std::move(), which may "
"unexpectedly cause lvalues to be moved; use "
"std::forward() instead");
replaceMoveWithForward(UnresolvedLookup, ParmVar, TypeParmDecl, Diag,
*Result.Context);
}
} // namespace clang::tidy::bugprone
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