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//===- RedundantStringInitCheck.cpp - clang-tidy ----------------*- C++ -*-===//
//
// 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 "RedundantStringInitCheck.h"
#include "../utils/Matchers.h"
#include "../utils/OptionsUtils.h"
#include "clang/ASTMatchers/ASTMatchers.h"
#include <optional>
using namespace clang::ast_matchers;
using namespace clang::tidy::matchers;
namespace clang::tidy::readability {
const char DefaultStringNames[] =
"::std::basic_string_view;::std::basic_string";
static std::vector<StringRef> removeNamespaces(ArrayRef<StringRef> Names) {
std::vector<StringRef> Result;
Result.reserve(Names.size());
for (StringRef Name : Names) {
StringRef::size_type ColonPos = Name.rfind(':');
Result.push_back(
Name.drop_front(ColonPos == StringRef::npos ? 0 : ColonPos + 1));
}
return Result;
}
static const CXXConstructExpr *
getConstructExpr(const CXXCtorInitializer &CtorInit) {
const Expr *InitExpr = CtorInit.getInit();
if (const auto *CleanUpExpr = dyn_cast<ExprWithCleanups>(InitExpr))
InitExpr = CleanUpExpr->getSubExpr();
return dyn_cast<CXXConstructExpr>(InitExpr);
}
static std::optional<SourceRange>
getConstructExprArgRange(const CXXConstructExpr &Construct) {
SourceLocation B, E;
for (const Expr *Arg : Construct.arguments()) {
if (B.isInvalid())
B = Arg->getBeginLoc();
if (Arg->getEndLoc().isValid())
E = Arg->getEndLoc();
}
if (B.isInvalid() || E.isInvalid())
return std::nullopt;
return SourceRange(B, E);
}
RedundantStringInitCheck::RedundantStringInitCheck(StringRef Name,
ClangTidyContext *Context)
: ClangTidyCheck(Name, Context),
StringNames(utils::options::parseStringList(
Options.get("StringNames", DefaultStringNames))) {}
void RedundantStringInitCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
Options.store(Opts, "StringNames", DefaultStringNames);
}
void RedundantStringInitCheck::registerMatchers(MatchFinder *Finder) {
const auto HasStringTypeName = hasAnyName(StringNames);
const auto HasStringCtorName = hasAnyName(removeNamespaces(StringNames));
// Match string constructor.
const auto StringConstructorExpr = expr(
anyOf(cxxConstructExpr(argumentCountIs(1),
hasDeclaration(cxxMethodDecl(HasStringCtorName))),
// If present, the second argument is the alloc object which must
// not be present explicitly.
cxxConstructExpr(argumentCountIs(2),
hasDeclaration(cxxMethodDecl(HasStringCtorName)),
hasArgument(1, cxxDefaultArgExpr()))));
// Match a string constructor expression with an empty string literal.
const auto EmptyStringCtorExpr = cxxConstructExpr(
StringConstructorExpr,
hasArgument(0, ignoringParenImpCasts(stringLiteral(hasSize(0)))));
const auto EmptyStringCtorExprWithTemporaries =
cxxConstructExpr(StringConstructorExpr,
hasArgument(0, ignoringImplicit(EmptyStringCtorExpr)));
const auto StringType = hasType(hasUnqualifiedDesugaredType(
recordType(hasDeclaration(cxxRecordDecl(HasStringTypeName)))));
const auto EmptyStringInit = traverse(
TK_AsIs, expr(ignoringImplicit(anyOf(
EmptyStringCtorExpr, EmptyStringCtorExprWithTemporaries))));
// Match a variable declaration with an empty string literal as initializer.
// Examples:
// string foo = "";
// string bar("");
Finder->addMatcher(
traverse(TK_AsIs,
namedDecl(varDecl(StringType, hasInitializer(EmptyStringInit))
.bind("vardecl"),
unless(parmVarDecl()))),
this);
// Match a field declaration with an empty string literal as initializer.
Finder->addMatcher(
namedDecl(fieldDecl(StringType, hasInClassInitializer(EmptyStringInit))
.bind("fieldDecl")),
this);
// Matches Constructor Initializers with an empty string literal as
// initializer.
// Examples:
// Foo() : SomeString("") {}
Finder->addMatcher(
cxxCtorInitializer(
isWritten(),
forField(allOf(StringType, optionally(hasInClassInitializer(
EmptyStringInit.bind("empty_init"))))),
withInitializer(EmptyStringInit))
.bind("ctorInit"),
this);
}
void RedundantStringInitCheck::check(const MatchFinder::MatchResult &Result) {
if (const auto *VDecl = Result.Nodes.getNodeAs<VarDecl>("vardecl")) {
// VarDecl's getSourceRange() spans 'string foo = ""' or 'string bar("")'.
// So start at getLocation() to span just 'foo = ""' or 'bar("")'.
SourceRange ReplaceRange(VDecl->getLocation(), VDecl->getEndLoc());
diag(VDecl->getLocation(), "redundant string initialization")
<< FixItHint::CreateReplacement(ReplaceRange, VDecl->getName());
}
if (const auto *FDecl = Result.Nodes.getNodeAs<FieldDecl>("fieldDecl")) {
// FieldDecl's getSourceRange() spans 'string foo = ""'.
// So start at getLocation() to span just 'foo = ""'.
SourceRange ReplaceRange(FDecl->getLocation(), FDecl->getEndLoc());
diag(FDecl->getLocation(), "redundant string initialization")
<< FixItHint::CreateReplacement(ReplaceRange, FDecl->getName());
}
if (const auto *CtorInit =
Result.Nodes.getNodeAs<CXXCtorInitializer>("ctorInit")) {
if (const FieldDecl *Member = CtorInit->getMember()) {
if (!Member->hasInClassInitializer() ||
Result.Nodes.getNodeAs<Expr>("empty_init")) {
// The String isn't declared in the class with an initializer or its
// declared with a redundant initializer, which will be removed. Either
// way the string will be default initialized, therefore we can remove
// the constructor initializer entirely.
diag(CtorInit->getMemberLocation(), "redundant string initialization")
<< FixItHint::CreateRemoval(CtorInit->getSourceRange());
return;
}
}
const CXXConstructExpr *Construct = getConstructExpr(*CtorInit);
if (!Construct)
return;
if (std::optional<SourceRange> RemovalRange =
getConstructExprArgRange(*Construct))
diag(CtorInit->getMemberLocation(), "redundant string initialization")
<< FixItHint::CreateRemoval(*RemovalRange);
}
}
} // namespace clang::tidy::readability
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