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//===- ExprClassification.cpp - Expression AST Node Implementation --------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This file implements Expr::classify.
#include "clang/AST/Expr.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/ExprObjC.h"
#include "llvm/Support/ErrorHandling.h"
using namespace clang;
using Cl = Expr::Classification;
static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E);
static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D);
static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T);
static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E);
static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E);
static Cl::Kinds ClassifyConditional(ASTContext &Ctx,
const Expr *trueExpr,
const Expr *falseExpr);
static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E,
Cl::Kinds Kind, SourceLocation &Loc);
Cl Expr::ClassifyImpl(ASTContext &Ctx, SourceLocation *Loc) const {
assert(!TR->isReferenceType() && "Expressions can't have reference type.");
Cl::Kinds kind = ClassifyInternal(Ctx, this);
// C99 An lvalue is an expression with an object type or an
// incomplete type other than void.
if (!Ctx.getLangOpts().CPlusPlus) {
// Thus, no functions.
if (TR->isFunctionType() || TR == Ctx.OverloadTy)
kind = Cl::CL_Function;
// No void either, but qualified void is OK because it is "other than void".
// Void "lvalues" are classified as addressable void values, which are void
// expressions whose address can be taken.
else if (TR->isVoidType() && !TR.hasQualifiers())
kind = (kind == Cl::CL_LValue ? Cl::CL_AddressableVoid : Cl::CL_Void);
// Enable this assertion for testing.
switch (kind) {
case Cl::CL_LValue: assert(getValueKind() == VK_LValue); break;
case Cl::CL_XValue: assert(getValueKind() == VK_XValue); break;
case Cl::CL_Function:
case Cl::CL_Void:
case Cl::CL_AddressableVoid:
case Cl::CL_DuplicateVectorComponents:
case Cl::CL_MemberFunction:
case Cl::CL_SubObjCPropertySetting:
case Cl::CL_ClassTemporary:
case Cl::CL_ArrayTemporary:
case Cl::CL_ObjCMessageRValue:
case Cl::CL_PRValue: assert(getValueKind() == VK_RValue); break;
Cl::ModifiableType modifiable = Cl::CM_Untested;
if (Loc)
modifiable = IsModifiable(Ctx, this, kind, *Loc);
return Classification(kind, modifiable);
/// Classify an expression which creates a temporary, based on its type.
static Cl::Kinds ClassifyTemporary(QualType T) {
if (T->isRecordType())
return Cl::CL_ClassTemporary;
if (T->isArrayType())
return Cl::CL_ArrayTemporary;
// No special classification: these don't behave differently from normal
// prvalues.
return Cl::CL_PRValue;
static Cl::Kinds ClassifyExprValueKind(const LangOptions &Lang,
const Expr *E,
ExprValueKind Kind) {
switch (Kind) {
case VK_RValue:
return Lang.CPlusPlus ? ClassifyTemporary(E->getType()) : Cl::CL_PRValue;
case VK_LValue:
return Cl::CL_LValue;
case VK_XValue:
return Cl::CL_XValue;
llvm_unreachable("Invalid value category of implicit cast.");
static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) {
// This function takes the first stab at classifying expressions.
const LangOptions &Lang = Ctx.getLangOpts();
switch (E->getStmtClass()) {
case Stmt::NoStmtClass:
#define ABSTRACT_STMT(Kind)
#define STMT(Kind, Base) case Expr::Kind##Class:
#define EXPR(Kind, Base)
#include "clang/AST/"
llvm_unreachable("cannot classify a statement");
// First come the expressions that are always lvalues, unconditionally.
case Expr::ObjCIsaExprClass:
// C++ [expr.prim.general]p1: A string literal is an lvalue.
case Expr::StringLiteralClass:
// @encode is equivalent to its string
case Expr::ObjCEncodeExprClass:
// __func__ and friends are too.
case Expr::PredefinedExprClass:
// Property references are lvalues
case Expr::ObjCSubscriptRefExprClass:
case Expr::ObjCPropertyRefExprClass:
// C++ [expr.typeid]p1: The result of a typeid expression is an lvalue of...
case Expr::CXXTypeidExprClass:
// Unresolved lookups and uncorrected typos get classified as lvalues.
// FIXME: Is this wise? Should they get their own kind?
case Expr::UnresolvedLookupExprClass:
case Expr::UnresolvedMemberExprClass:
case Expr::TypoExprClass:
case Expr::DependentCoawaitExprClass:
case Expr::CXXDependentScopeMemberExprClass:
case Expr::DependentScopeDeclRefExprClass:
// ObjC instance variables are lvalues
// FIXME: ObjC++0x might have different rules
case Expr::ObjCIvarRefExprClass:
case Expr::FunctionParmPackExprClass:
case Expr::MSPropertyRefExprClass:
case Expr::MSPropertySubscriptExprClass:
case Expr::OMPArraySectionExprClass:
return Cl::CL_LValue;
// C99 says that compound literals are lvalues.
// In C++, they're prvalue temporaries, except for file-scope arrays.
case Expr::CompoundLiteralExprClass:
return !E->isLValue() ? ClassifyTemporary(E->getType()) : Cl::CL_LValue;
// Expressions that are prvalues.
case Expr::CXXBoolLiteralExprClass:
case Expr::CXXPseudoDestructorExprClass:
case Expr::UnaryExprOrTypeTraitExprClass:
case Expr::CXXNewExprClass:
case Expr::CXXThisExprClass:
case Expr::CXXNullPtrLiteralExprClass:
case Expr::ImaginaryLiteralClass:
case Expr::GNUNullExprClass:
case Expr::OffsetOfExprClass:
case Expr::CXXThrowExprClass:
case Expr::ShuffleVectorExprClass:
case Expr::ConvertVectorExprClass:
case Expr::IntegerLiteralClass:
case Expr::FixedPointLiteralClass:
case Expr::CharacterLiteralClass:
case Expr::AddrLabelExprClass:
case Expr::CXXDeleteExprClass:
case Expr::ImplicitValueInitExprClass:
case Expr::BlockExprClass:
case Expr::FloatingLiteralClass:
case Expr::CXXNoexceptExprClass:
case Expr::CXXScalarValueInitExprClass:
case Expr::TypeTraitExprClass:
case Expr::ArrayTypeTraitExprClass:
case Expr::ExpressionTraitExprClass:
case Expr::ObjCSelectorExprClass:
case Expr::ObjCProtocolExprClass:
case Expr::ObjCStringLiteralClass:
case Expr::ObjCBoxedExprClass:
case Expr::ObjCArrayLiteralClass:
case Expr::ObjCDictionaryLiteralClass:
case Expr::ObjCBoolLiteralExprClass:
case Expr::ObjCAvailabilityCheckExprClass:
case Expr::ParenListExprClass:
case Expr::SizeOfPackExprClass:
case Expr::SubstNonTypeTemplateParmPackExprClass:
case Expr::AsTypeExprClass:
case Expr::ObjCIndirectCopyRestoreExprClass:
case Expr::AtomicExprClass:
case Expr::CXXFoldExprClass:
case Expr::ArrayInitLoopExprClass:
case Expr::ArrayInitIndexExprClass:
case Expr::NoInitExprClass:
case Expr::DesignatedInitUpdateExprClass:
case Expr::SourceLocExprClass:
case Expr::ConceptSpecializationExprClass:
return Cl::CL_PRValue;
case Expr::ConstantExprClass:
return ClassifyInternal(Ctx, cast<ConstantExpr>(E)->getSubExpr());
// Next come the complicated cases.
case Expr::SubstNonTypeTemplateParmExprClass:
return ClassifyInternal(Ctx,
// C, C++98 [expr.sub]p1: The result is an lvalue of type "T".
// C++11 (DR1213): in the case of an array operand, the result is an lvalue
// if that operand is an lvalue and an xvalue otherwise.
// Subscripting vector types is more like member access.
case Expr::ArraySubscriptExprClass:
if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType())
return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase());
if (Lang.CPlusPlus11) {
// Step over the array-to-pointer decay if present, but not over the
// temporary materialization.
auto *Base = cast<ArraySubscriptExpr>(E)->getBase()->IgnoreImpCasts();
if (Base->getType()->isArrayType())
return ClassifyInternal(Ctx, Base);
return Cl::CL_LValue;
// C++ [expr.prim.general]p3: The result is an lvalue if the entity is a
// function or variable and a prvalue otherwise.
case Expr::DeclRefExprClass:
if (E->getType() == Ctx.UnknownAnyTy)
return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl())
? Cl::CL_PRValue : Cl::CL_LValue;
return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl());
// Member access is complex.
case Expr::MemberExprClass:
return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E));
case Expr::UnaryOperatorClass:
switch (cast<UnaryOperator>(E)->getOpcode()) {
// C++ [expr.unary.op]p1: The unary * operator performs indirection:
// [...] the result is an lvalue referring to the object or function
// to which the expression points.
case UO_Deref:
return Cl::CL_LValue;
// GNU extensions, simply look through them.
case UO_Extension:
return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr());
// Treat _Real and _Imag basically as if they were member
// expressions: l-value only if the operand is a true l-value.
case UO_Real:
case UO_Imag: {
const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens();
Cl::Kinds K = ClassifyInternal(Ctx, Op);
if (K != Cl::CL_LValue) return K;
if (isa<ObjCPropertyRefExpr>(Op))
return Cl::CL_SubObjCPropertySetting;
return Cl::CL_LValue;
// C++ [expr.pre.incr]p1: The result is the updated operand; it is an
// lvalue, [...]
// Not so in C.
case UO_PreInc:
case UO_PreDec:
return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue;
return Cl::CL_PRValue;
case Expr::OpaqueValueExprClass:
return ClassifyExprValueKind(Lang, E, E->getValueKind());
// Pseudo-object expressions can produce l-values with reference magic.
case Expr::PseudoObjectExprClass:
return ClassifyExprValueKind(Lang, E,
// Implicit casts are lvalues if they're lvalue casts. Other than that, we
// only specifically record class temporaries.
case Expr::ImplicitCastExprClass:
return ClassifyExprValueKind(Lang, E, E->getValueKind());
// C++ [expr.prim.general]p4: The presence of parentheses does not affect
// whether the expression is an lvalue.
case Expr::ParenExprClass:
return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr());
// C11 [A generic selection] is an lvalue, a function designator,
// or a void expression if its result expression is, respectively, an
// lvalue, a function designator, or a void expression.
case Expr::GenericSelectionExprClass:
if (cast<GenericSelectionExpr>(E)->isResultDependent())
return Cl::CL_PRValue;
return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr());
case Expr::BinaryOperatorClass:
case Expr::CompoundAssignOperatorClass:
// C doesn't have any binary expressions that are lvalues.
if (Lang.CPlusPlus)
return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E));
return Cl::CL_PRValue;
case Expr::CallExprClass:
case Expr::CXXOperatorCallExprClass:
case Expr::CXXMemberCallExprClass:
case Expr::UserDefinedLiteralClass:
case Expr::CUDAKernelCallExprClass:
return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType(Ctx));
// __builtin_choose_expr is equivalent to the chosen expression.
case Expr::ChooseExprClass:
return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr());
// Extended vector element access is an lvalue unless there are duplicates
// in the shuffle expression.
case Expr::ExtVectorElementExprClass:
if (cast<ExtVectorElementExpr>(E)->containsDuplicateElements())
return Cl::CL_DuplicateVectorComponents;
if (cast<ExtVectorElementExpr>(E)->isArrow())
return Cl::CL_LValue;
return ClassifyInternal(Ctx, cast<ExtVectorElementExpr>(E)->getBase());
// Simply look at the actual default argument.
case Expr::CXXDefaultArgExprClass:
return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr());
// Same idea for default initializers.
case Expr::CXXDefaultInitExprClass:
return ClassifyInternal(Ctx, cast<CXXDefaultInitExpr>(E)->getExpr());
// Same idea for temporary binding.
case Expr::CXXBindTemporaryExprClass:
return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr());
// And the cleanups guard.
case Expr::ExprWithCleanupsClass:
return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr());
// Casts depend completely on the target type. All casts work the same.
case Expr::CStyleCastExprClass:
case Expr::CXXFunctionalCastExprClass:
case Expr::CXXStaticCastExprClass:
case Expr::CXXDynamicCastExprClass:
case Expr::CXXReinterpretCastExprClass:
case Expr::CXXConstCastExprClass:
case Expr::ObjCBridgedCastExprClass:
case Expr::BuiltinBitCastExprClass:
// Only in C++ can casts be interesting at all.
if (!Lang.CPlusPlus) return Cl::CL_PRValue;
return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten());
case Expr::CXXUnresolvedConstructExprClass:
return ClassifyUnnamed(Ctx,
case Expr::BinaryConditionalOperatorClass: {
if (!Lang.CPlusPlus) return Cl::CL_PRValue;
const auto *co = cast<BinaryConditionalOperator>(E);
return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
case Expr::ConditionalOperatorClass: {
// Once again, only C++ is interesting.
if (!Lang.CPlusPlus) return Cl::CL_PRValue;
const auto *co = cast<ConditionalOperator>(E);
return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
// ObjC message sends are effectively function calls, if the target function
// is known.
case Expr::ObjCMessageExprClass:
if (const ObjCMethodDecl *Method =
cast<ObjCMessageExpr>(E)->getMethodDecl()) {
Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getReturnType());
return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind;
return Cl::CL_PRValue;
// Some C++ expressions are always class temporaries.
case Expr::CXXConstructExprClass:
case Expr::CXXInheritedCtorInitExprClass:
case Expr::CXXTemporaryObjectExprClass:
case Expr::LambdaExprClass:
case Expr::CXXStdInitializerListExprClass:
return Cl::CL_ClassTemporary;
case Expr::VAArgExprClass:
return ClassifyUnnamed(Ctx, E->getType());
case Expr::DesignatedInitExprClass:
return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit());
case Expr::StmtExprClass: {
const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt();
if (const auto *LastExpr = dyn_cast_or_null<Expr>(S->body_back()))
return ClassifyUnnamed(Ctx, LastExpr->getType());
return Cl::CL_PRValue;
case Expr::CXXUuidofExprClass:
return Cl::CL_LValue;
case Expr::PackExpansionExprClass:
return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern());
case Expr::MaterializeTemporaryExprClass:
return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference()
? Cl::CL_LValue
: Cl::CL_XValue;
case Expr::InitListExprClass:
// An init list can be an lvalue if it is bound to a reference and
// contains only one element. In that case, we look at that element
// for an exact classification. Init list creation takes care of the
// value kind for us, so we only need to fine-tune.
if (E->isRValue())
return ClassifyExprValueKind(Lang, E, E->getValueKind());
assert(cast<InitListExpr>(E)->getNumInits() == 1 &&
"Only 1-element init lists can be glvalues.");
return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0));
case Expr::CoawaitExprClass:
case Expr::CoyieldExprClass:
return ClassifyInternal(Ctx, cast<CoroutineSuspendExpr>(E)->getResumeExpr());
llvm_unreachable("unhandled expression kind in classification");
/// ClassifyDecl - Return the classification of an expression referencing the
/// given declaration.
static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) {
// C++ [expr.prim.general]p6: The result is an lvalue if the entity is a
// function, variable, or data member and a prvalue otherwise.
// In C, functions are not lvalues.
// In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an
// lvalue unless it's a reference type (C++ [temp.param]p6), so we need to
// special-case this.
if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance())
return Cl::CL_MemberFunction;
bool islvalue;
if (const auto *NTTParm = dyn_cast<NonTypeTemplateParmDecl>(D))
islvalue = NTTParm->getType()->isReferenceType();
islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) ||
isa<IndirectFieldDecl>(D) ||
isa<BindingDecl>(D) ||
(Ctx.getLangOpts().CPlusPlus &&
(isa<FunctionDecl>(D) || isa<MSPropertyDecl>(D) ||
return islvalue ? Cl::CL_LValue : Cl::CL_PRValue;
/// ClassifyUnnamed - Return the classification of an expression yielding an
/// unnamed value of the given type. This applies in particular to function
/// calls and casts.
static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T) {
// In C, function calls are always rvalues.
if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue;
// C++ []p10: A function call is an lvalue if the result type is an
// lvalue reference type or an rvalue reference to function type, an xvalue
// if the result type is an rvalue reference to object type, and a prvalue
// otherwise.
if (T->isLValueReferenceType())
return Cl::CL_LValue;
const auto *RV = T->getAs<RValueReferenceType>();
if (!RV) // Could still be a class temporary, though.
return ClassifyTemporary(T);
return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue;
static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) {
if (E->getType() == Ctx.UnknownAnyTy)
return (isa<FunctionDecl>(E->getMemberDecl())
? Cl::CL_PRValue : Cl::CL_LValue);
// Handle C first, it's easier.
if (!Ctx.getLangOpts().CPlusPlus) {
// C99
// For dot access, the expression is an lvalue if the first part is. For
// arrow access, it always is an lvalue.
if (E->isArrow())
return Cl::CL_LValue;
// ObjC property accesses are not lvalues, but get special treatment.
Expr *Base = E->getBase()->IgnoreParens();
if (isa<ObjCPropertyRefExpr>(Base))
return Cl::CL_SubObjCPropertySetting;
return ClassifyInternal(Ctx, Base);
NamedDecl *Member = E->getMemberDecl();
// C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2.
// C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then
// E1.E2 is an lvalue.
if (const auto *Value = dyn_cast<ValueDecl>(Member))
if (Value->getType()->isReferenceType())
return Cl::CL_LValue;
// Otherwise, one of the following rules applies.
// -- If E2 is a static member [...] then E1.E2 is an lvalue.
if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord())
return Cl::CL_LValue;
// -- If E2 is a non-static data member [...]. If E1 is an lvalue, then
// E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue;
// otherwise, it is a prvalue.
if (isa<FieldDecl>(Member)) {
// *E1 is an lvalue
if (E->isArrow())
return Cl::CL_LValue;
Expr *Base = E->getBase()->IgnoreParenImpCasts();
if (isa<ObjCPropertyRefExpr>(Base))
return Cl::CL_SubObjCPropertySetting;
return ClassifyInternal(Ctx, E->getBase());
// -- If E2 is a [...] member function, [...]
// -- If it refers to a static member function [...], then E1.E2 is an
// lvalue; [...]
// -- Otherwise [...] E1.E2 is a prvalue.
if (const auto *Method = dyn_cast<CXXMethodDecl>(Member))
return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction;
// -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue.
// So is everything else we haven't handled yet.
return Cl::CL_PRValue;
static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) {
assert(Ctx.getLangOpts().CPlusPlus &&
"This is only relevant for C++.");
// C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand.
// Except we override this for writes to ObjC properties.
if (E->isAssignmentOp())
return (E->getLHS()->getObjectKind() == OK_ObjCProperty
? Cl::CL_PRValue : Cl::CL_LValue);
// C++ [expr.comma]p1: the result is of the same value category as its right
// operand, [...].
if (E->getOpcode() == BO_Comma)
return ClassifyInternal(Ctx, E->getRHS());
// C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand
// is a pointer to a data member is of the same value category as its first
// operand.
if (E->getOpcode() == BO_PtrMemD)
return (E->getType()->isFunctionType() ||
? Cl::CL_MemberFunction
: ClassifyInternal(Ctx, E->getLHS());
// C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its
// second operand is a pointer to data member and a prvalue otherwise.
if (E->getOpcode() == BO_PtrMemI)
return (E->getType()->isFunctionType() ||
? Cl::CL_MemberFunction
: Cl::CL_LValue;
// All other binary operations are prvalues.
return Cl::CL_PRValue;
static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True,
const Expr *False) {
assert(Ctx.getLangOpts().CPlusPlus &&
"This is only relevant for C++.");
// C++ [expr.cond]p2
// If either the second or the third operand has type (cv) void,
// one of the following shall hold:
if (True->getType()->isVoidType() || False->getType()->isVoidType()) {
// The second or the third operand (but not both) is a (possibly
// parenthesized) throw-expression; the result is of the [...] value
// category of the other.
bool TrueIsThrow = isa<CXXThrowExpr>(True->IgnoreParenImpCasts());
bool FalseIsThrow = isa<CXXThrowExpr>(False->IgnoreParenImpCasts());
if (const Expr *NonThrow = TrueIsThrow ? (FalseIsThrow ? nullptr : False)
: (FalseIsThrow ? True : nullptr))
return ClassifyInternal(Ctx, NonThrow);
// [Otherwise] the result [...] is a prvalue.
return Cl::CL_PRValue;
// Note that at this point, we have already performed all conversions
// according to [expr.cond]p3.
// C++ [expr.cond]p4: If the second and third operands are glvalues of the
// same value category [...], the result is of that [...] value category.
// C++ [expr.cond]p5: Otherwise, the result is a prvalue.
Cl::Kinds LCl = ClassifyInternal(Ctx, True),
RCl = ClassifyInternal(Ctx, False);
return LCl == RCl ? LCl : Cl::CL_PRValue;
static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E,
Cl::Kinds Kind, SourceLocation &Loc) {
// As a general rule, we only care about lvalues. But there are some rvalues
// for which we want to generate special results.
if (Kind == Cl::CL_PRValue) {
// For the sake of better diagnostics, we want to specifically recognize
// use of the GCC cast-as-lvalue extension.
if (const auto *CE = dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) {
if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) {
Loc = CE->getExprLoc();
return Cl::CM_LValueCast;
if (Kind != Cl::CL_LValue)
return Cl::CM_RValue;
// This is the lvalue case.
// Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6)
if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType())
return Cl::CM_Function;
// Assignment to a property in ObjC is an implicit setter access. But a
// setter might not exist.
if (const auto *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) {
if (Expr->isImplicitProperty() &&
Expr->getImplicitPropertySetter() == nullptr)
return Cl::CM_NoSetterProperty;
CanQualType CT = Ctx.getCanonicalType(E->getType());
// Const stuff is obviously not modifiable.
if (CT.isConstQualified())
return Cl::CM_ConstQualified;
if (Ctx.getLangOpts().OpenCL &&
CT.getQualifiers().getAddressSpace() == LangAS::opencl_constant)
return Cl::CM_ConstAddrSpace;
// Arrays are not modifiable, only their elements are.
if (CT->isArrayType())
return Cl::CM_ArrayType;
// Incomplete types are not modifiable.
if (CT->isIncompleteType())
return Cl::CM_IncompleteType;
// Records with any const fields (recursively) are not modifiable.
if (const RecordType *R = CT->getAs<RecordType>())
if (R->hasConstFields())
return Cl::CM_ConstQualifiedField;
return Cl::CM_Modifiable;
Expr::LValueClassification Expr::ClassifyLValue(ASTContext &Ctx) const {
Classification VC = Classify(Ctx);
switch (VC.getKind()) {
case Cl::CL_LValue: return LV_Valid;
case Cl::CL_XValue: return LV_InvalidExpression;
case Cl::CL_Function: return LV_NotObjectType;
case Cl::CL_Void: return LV_InvalidExpression;
case Cl::CL_AddressableVoid: return LV_IncompleteVoidType;
case Cl::CL_DuplicateVectorComponents: return LV_DuplicateVectorComponents;
case Cl::CL_MemberFunction: return LV_MemberFunction;
case Cl::CL_SubObjCPropertySetting: return LV_SubObjCPropertySetting;
case Cl::CL_ClassTemporary: return LV_ClassTemporary;
case Cl::CL_ArrayTemporary: return LV_ArrayTemporary;
case Cl::CL_ObjCMessageRValue: return LV_InvalidMessageExpression;
case Cl::CL_PRValue: return LV_InvalidExpression;
llvm_unreachable("Unhandled kind");
Expr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const {
SourceLocation dummy;
Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy);
switch (VC.getKind()) {
case Cl::CL_LValue: break;
case Cl::CL_XValue: return MLV_InvalidExpression;
case Cl::CL_Function: return MLV_NotObjectType;
case Cl::CL_Void: return MLV_InvalidExpression;
case Cl::CL_AddressableVoid: return MLV_IncompleteVoidType;
case Cl::CL_DuplicateVectorComponents: return MLV_DuplicateVectorComponents;
case Cl::CL_MemberFunction: return MLV_MemberFunction;
case Cl::CL_SubObjCPropertySetting: return MLV_SubObjCPropertySetting;
case Cl::CL_ClassTemporary: return MLV_ClassTemporary;
case Cl::CL_ArrayTemporary: return MLV_ArrayTemporary;
case Cl::CL_ObjCMessageRValue: return MLV_InvalidMessageExpression;
case Cl::CL_PRValue:
return VC.getModifiable() == Cl::CM_LValueCast ?
MLV_LValueCast : MLV_InvalidExpression;
assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind");
switch (VC.getModifiable()) {
case Cl::CM_Untested: llvm_unreachable("Did not test modifiability");
case Cl::CM_Modifiable: return MLV_Valid;
case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match");
case Cl::CM_Function: return MLV_NotObjectType;
case Cl::CM_LValueCast:
llvm_unreachable("CM_LValueCast and CL_LValue don't match");
case Cl::CM_NoSetterProperty: return MLV_NoSetterProperty;
case Cl::CM_ConstQualified: return MLV_ConstQualified;
case Cl::CM_ConstQualifiedField: return MLV_ConstQualifiedField;
case Cl::CM_ConstAddrSpace: return MLV_ConstAddrSpace;
case Cl::CM_ArrayType: return MLV_ArrayType;
case Cl::CM_IncompleteType: return MLV_IncompleteType;
llvm_unreachable("Unhandled modifiable type");