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//===--- UnnecessaryValueParamCheck.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 "UnnecessaryValueParamCheck.h"
#include "../utils/DeclRefExprUtils.h"
#include "../utils/FixItHintUtils.h"
#include "../utils/Matchers.h"
using namespace clang::ast_matchers;
namespace clang {
namespace tidy {
namespace performance {
namespace {
std::string paramNameOrIndex(StringRef Name, size_t Index) {
return (Name.empty() ? llvm::Twine('#') + llvm::Twine(Index + 1)
: llvm::Twine('\'') + Name + llvm::Twine('\''))
.str();
}
} // namespace
void UnnecessaryValueParamCheck::registerMatchers(MatchFinder *Finder) {
const auto ExpensiveValueParamDecl =
parmVarDecl(hasType(hasCanonicalType(allOf(matchers::isExpensiveToCopy(),
unless(referenceType())))),
decl().bind("param"));
Finder->addMatcher(
functionDecl(isDefinition(), unless(cxxMethodDecl(isOverride())),
unless(isInstantiated()),
has(typeLoc(forEach(ExpensiveValueParamDecl))),
decl().bind("functionDecl")),
this);
}
void UnnecessaryValueParamCheck::check(const MatchFinder::MatchResult &Result) {
const auto *Param = Result.Nodes.getNodeAs<ParmVarDecl>("param");
const auto *Function = Result.Nodes.getNodeAs<FunctionDecl>("functionDecl");
const size_t Index = std::find(Function->parameters().begin(),
Function->parameters().end(), Param) -
Function->parameters().begin();
bool IsConstQualified =
Param->getType().getCanonicalType().isConstQualified();
// Skip declarations delayed by late template parsing without a body.
if (!Function->getBody())
return;
// Do not trigger on non-const value parameters when:
// 1. they are in a constructor definition since they can likely trigger
// misc-move-constructor-init which will suggest to move the argument.
// 2. they are not only used as const.
if (!IsConstQualified && (llvm::isa<CXXConstructorDecl>(Function) ||
!Function->doesThisDeclarationHaveABody() ||
!decl_ref_expr_utils::isOnlyUsedAsConst(
*Param, *Function->getBody(), *Result.Context)))
return;
auto Diag =
diag(Param->getLocation(),
IsConstQualified ? "the const qualified parameter %0 is "
"copied for each invocation; consider "
"making it a reference"
: "the parameter %0 is copied for each "
"invocation but only used as a const reference; "
"consider making it a const reference")
<< paramNameOrIndex(Param->getName(), Index);
// Do not propose fixes in macros since we cannot place them correctly.
if (Param->getLocStart().isMacroID())
return;
for (const auto *FunctionDecl = Function; FunctionDecl != nullptr;
FunctionDecl = FunctionDecl->getPreviousDecl()) {
const auto &CurrentParam = *FunctionDecl->getParamDecl(Index);
Diag << utils::create_fix_it::changeVarDeclToReference(CurrentParam,
*Result.Context);
if (!IsConstQualified)
Diag << utils::create_fix_it::changeVarDeclToConst(CurrentParam);
}
}
} // namespace performance
} // namespace tidy
} // namespace clang
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