llvm-project/clang-tools-extra/clang-tidy/performance/ForRangeCopyCheck.cpp

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//===--- ForRangeCopyCheck.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 "ForRangeCopyCheck.h"
#include "../utils/DeclRefExprUtils.h"
#include "../utils/FixItHintUtils.h"
#include "../utils/TypeTraits.h"
using namespace clang::ast_matchers;
namespace clang {
namespace tidy {
namespace performance {
ForRangeCopyCheck::ForRangeCopyCheck(StringRef Name, ClangTidyContext *Context)
: ClangTidyCheck(Name, Context),
WarnOnAllAutoCopies(Options.get("WarnOnAllAutoCopies", 0)) {}
void ForRangeCopyCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
Options.store(Opts, "WarnOnAllAutoCopies", WarnOnAllAutoCopies);
}
void ForRangeCopyCheck::registerMatchers(MatchFinder *Finder) {
// Match loop variables that are not references or pointers or are already
// initialized through MaterializeTemporaryExpr which indicates a type
// conversion.
auto LoopVar = varDecl(
hasType(hasCanonicalType(unless(anyOf(referenceType(), pointerType())))),
unless(hasInitializer(expr(hasDescendant(materializeTemporaryExpr())))));
Finder->addMatcher(cxxForRangeStmt(hasLoopVariable(LoopVar.bind("loopVar")))
.bind("forRange"),
this);
}
void ForRangeCopyCheck::check(const MatchFinder::MatchResult &Result) {
const auto *Var = Result.Nodes.getNodeAs<VarDecl>("loopVar");
// Ignore code in macros since we can't place the fixes correctly.
if (Var->getLocStart().isMacroID())
return;
if (handleConstValueCopy(*Var, *Result.Context))
return;
const auto *ForRange = Result.Nodes.getNodeAs<CXXForRangeStmt>("forRange");
handleCopyIsOnlyConstReferenced(*Var, *ForRange, *Result.Context);
}
bool ForRangeCopyCheck::handleConstValueCopy(const VarDecl &LoopVar,
ASTContext &Context) {
if (WarnOnAllAutoCopies) {
// For aggressive check just test that loop variable has auto type.
if (!isa<AutoType>(LoopVar.getType()))
return false;
} else if (!LoopVar.getType().isConstQualified()) {
return false;
}
llvm::Optional<bool> Expensive =
utils::type_traits::isExpensiveToCopy(LoopVar.getType(), Context);
if (!Expensive || !*Expensive)
return false;
auto Diagnostic =
diag(LoopVar.getLocation(),
"the loop variable's type is not a reference type; this creates a "
"copy in each iteration; consider making this a reference")
<< utils::fixit::changeVarDeclToReference(LoopVar, Context);
if (!LoopVar.getType().isConstQualified())
Diagnostic << utils::fixit::changeVarDeclToConst(LoopVar);
return true;
}
bool ForRangeCopyCheck::handleCopyIsOnlyConstReferenced(
const VarDecl &LoopVar, const CXXForRangeStmt &ForRange,
ASTContext &Context) {
llvm::Optional<bool> Expensive =
utils::type_traits::isExpensiveToCopy(LoopVar.getType(), Context);
if (LoopVar.getType().isConstQualified() || !Expensive || !*Expensive)
return false;
if (!utils::decl_ref_expr::isOnlyUsedAsConst(LoopVar, *ForRange.getBody(),
Context))
return false;
diag(LoopVar.getLocation(),
"loop variable is copied but only used as const reference; consider "
"making it a const reference")
<< utils::fixit::changeVarDeclToConst(LoopVar)
<< utils::fixit::changeVarDeclToReference(LoopVar, Context);
return true;
}
} // namespace performance
} // namespace tidy
} // namespace clang