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104 lines
4.2 KiB
C++
104 lines
4.2 KiB
C++
//===--- ImplicitConversionInLoopCheck.cpp - clang-tidy--------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "ImplicitConversionInLoopCheck.h"
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#include "clang/AST/ASTContext.h"
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#include "clang/AST/Decl.h"
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#include "clang/ASTMatchers/ASTMatchFinder.h"
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#include "clang/ASTMatchers/ASTMatchers.h"
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#include "clang/Lex/Lexer.h"
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using namespace clang::ast_matchers;
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namespace clang {
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namespace tidy {
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namespace performance {
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// Checks if the stmt is a ImplicitCastExpr with a CastKind that is not a NoOp.
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// The subtelty is that in some cases (user defined conversions), we can
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// get to ImplicitCastExpr inside each other, with the outer one a NoOp. In this
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// case we skip the first cast expr.
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static bool IsNonTrivialImplicitCast(const Stmt *ST) {
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if (const auto *ICE = dyn_cast<ImplicitCastExpr>(ST)) {
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return (ICE->getCastKind() != CK_NoOp) ||
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IsNonTrivialImplicitCast(ICE->getSubExpr());
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}
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return false;
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}
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void ImplicitConversionInLoopCheck::registerMatchers(MatchFinder *Finder) {
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// We look for const ref loop variables that (optionally inside an
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// ExprWithCleanup) materialize a temporary, and contain a implicit
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// conversion. The check on the implicit conversion is done in check() because
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// we can't access implicit conversion subnode via matchers: has() skips casts
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// and materialize! We also bind on the call to operator* to get the proper
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// type in the diagnostic message. We use both cxxOperatorCallExpr for user
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// defined operator and unaryOperator when the iterator is a pointer, like
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// for arrays or std::array.
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//
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// Note that when the implicit conversion is done through a user defined
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// conversion operator, the node is a CXXMemberCallExpr, not a
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// CXXOperatorCallExpr, so it should not get caught by the
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// cxxOperatorCallExpr() matcher.
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Finder->addMatcher(
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cxxForRangeStmt(hasLoopVariable(
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varDecl(
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hasType(qualType(references(qualType(isConstQualified())))),
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hasInitializer(
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expr(anyOf(hasDescendant(
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cxxOperatorCallExpr().bind("operator-call")),
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hasDescendant(unaryOperator(hasOperatorName("*"))
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.bind("operator-call"))))
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.bind("init")))
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.bind("faulty-var"))),
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this);
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}
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void ImplicitConversionInLoopCheck::check(
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const MatchFinder::MatchResult &Result) {
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const auto *VD = Result.Nodes.getNodeAs<VarDecl>("faulty-var");
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const auto *Init = Result.Nodes.getNodeAs<Expr>("init");
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const auto *OperatorCall =
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Result.Nodes.getNodeAs<Expr>("operator-call");
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if (const auto *Cleanup = dyn_cast<ExprWithCleanups>(Init))
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Init = Cleanup->getSubExpr();
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const auto *Materialized = dyn_cast<MaterializeTemporaryExpr>(Init);
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if (!Materialized)
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return;
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// We ignore NoOp casts. Those are generated if the * operator on the
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// iterator returns a value instead of a reference, and the loop variable
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// is a reference. This situation is fine (it probably produces the same
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// code at the end).
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if (IsNonTrivialImplicitCast(Materialized->getTemporary()))
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ReportAndFix(Result.Context, VD, OperatorCall);
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}
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void ImplicitConversionInLoopCheck::ReportAndFix(
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const ASTContext *Context, const VarDecl *VD,
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const Expr *OperatorCall) {
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// We only match on const ref, so we should print a const ref version of the
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// type.
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QualType ConstType = OperatorCall->getType().withConst();
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QualType ConstRefType = Context->getLValueReferenceType(ConstType);
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const char Message[] =
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"the type of the loop variable %0 is different from the one returned "
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"by the iterator and generates an implicit conversion; you can either "
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"change the type to the matching one (%1 but 'const auto&' is always a "
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"valid option) or remove the reference to make it explicit that you are "
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"creating a new value";
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diag(VD->getBeginLoc(), Message) << VD << ConstRefType;
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}
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} // namespace performance
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} // namespace tidy
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} // namespace clang
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