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[ObjC] Messages to 'self' in class methods that return 'instancetype' should 

use the pointer to the class as the result type of the message

Prior to this commit, messages to self in class methods were treated as instance
methods to a Class value. When these methods returned instancetype the compiler
only saw id through the instancetype, and not the Interface *. This caused
problems when that return value was a receiver in a message send, as the
compiler couldn't select the right method declaration and had to rely on a
selection from the global method pool.

This commit modifies the semantics of such message sends and uses class messages
that are dispatched to the interface that corresponds to the class that contains
the class method. This ensures that instancetypes are correctly interpreted by
the compiler. This change is safe under ARC (as self can't be reassigned),
however, it also applies to MRR code as we are assuming that the user isn't
doing anything unreasonable.

rdar://20940997

Differential Revision: https://reviews.llvm.org/D36790

llvm-svn: 349841
This commit is contained in:
Alex Lorenz 2018-12-20 22:11:11 +00:00
parent 8c020758a0
commit f50d1aca99
3 changed files with 88 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
clang/include/clang/Sema/Sema.h
View File

@ -9842,21 +9842,20 @@ public:
/// \param Method - May be null.
/// \param [out] ReturnType - The return type of the send.
/// \return true iff there were any incompatible types.
bool CheckMessageArgumentTypes(QualType ReceiverType,
bool CheckMessageArgumentTypes(const Expr *Receiver, QualType ReceiverType,
MultiExprArg Args, Selector Sel,
ArrayRef<SourceLocation> SelectorLocs,
ObjCMethodDecl *Method, bool isClassMessage,
bool isSuperMessage,
SourceLocation lbrac, SourceLocation rbrac,
SourceRange RecRange,
bool isSuperMessage, SourceLocation lbrac,
SourceLocation rbrac, SourceRange RecRange,
QualType &ReturnType, ExprValueKind &VK);
/// Determine the result of a message send expression based on
/// the type of the receiver, the method expected to receive the message,
/// and the form of the message send.
QualType getMessageSendResultType(QualType ReceiverType,
ObjCMethodDecl *Method,
bool isClassMessage, bool isSuperMessage);
QualType getMessageSendResultType(const Expr *Receiver, QualType ReceiverType,
ObjCMethodDecl *Method, bool isClassMessage,
bool isSuperMessage);
/// If the given expression involves a message send to a method
/// with a related result type, emit a note describing what happened.

65
clang/lib/Sema/SemaExprObjC.cpp
View File

@ -1346,7 +1346,8 @@ static QualType getBaseMessageSendResultType(Sema &S,
return transferNullability(ReceiverType);
}
QualType Sema::getMessageSendResultType(QualType ReceiverType,
QualType Sema::getMessageSendResultType(const Expr *Receiver,
QualType ReceiverType,
ObjCMethodDecl *Method,
bool isClassMessage,
bool isSuperMessage) {
@ -1357,8 +1358,33 @@ QualType Sema::getMessageSendResultType(QualType ReceiverType,
isSuperMessage);
// If this is a class message, ignore the nullability of the receiver.
if (isClassMessage)
if (isClassMessage) {
// In a class method, class messages to 'self' that return instancetype can
// be typed as the current class. We can safely do this in ARC because self
// can't be reassigned, and we do it unsafely outside of ARC because in
// practice people never reassign self in class methods and there's some
// virtue in not being aggressively pedantic.
if (Receiver && Receiver->isObjCSelfExpr()) {
assert(ReceiverType->isObjCClassType() && "expected a Class self");
QualType T = Method->getSendResultType(ReceiverType);
AttributedType::stripOuterNullability(T);
if (T == Context.getObjCInstanceType()) {
const ObjCMethodDecl *MD = cast<ObjCMethodDecl>(
cast<ImplicitParamDecl>(
cast<DeclRefExpr>(Receiver->IgnoreParenImpCasts())->getDecl())
->getDeclContext());
assert(MD->isClassMethod() && "expected a class method");
QualType NewResultType = Context.getObjCObjectPointerType(
Context.getObjCInterfaceType(MD->getClassInterface()));
if (auto Nullability = resultType->getNullability(Context))
NewResultType = Context.getAttributedType(
AttributedType::getNullabilityAttrKind(*Nullability),
NewResultType, NewResultType);
return NewResultType;
}
}
return resultType;
}
// There is nothing left to do if the result type cannot have a nullability
// specifier.
@ -1505,15 +1531,12 @@ void Sema::EmitRelatedResultTypeNote(const Expr *E) {
<< MsgSend->getType();
}
bool Sema::CheckMessageArgumentTypes(QualType ReceiverType,
MultiExprArg Args,
Selector Sel,
ArrayRef<SourceLocation> SelectorLocs,
ObjCMethodDecl *Method,
bool isClassMessage, bool isSuperMessage,
SourceLocation lbrac, SourceLocation rbrac,
SourceRange RecRange,
QualType &ReturnType, ExprValueKind &VK) {
bool Sema::CheckMessageArgumentTypes(
const Expr *Receiver, QualType ReceiverType, MultiExprArg Args,
Selector Sel, ArrayRef<SourceLocation> SelectorLocs, ObjCMethodDecl *Method,
bool isClassMessage, bool isSuperMessage, SourceLocation lbrac,
SourceLocation rbrac, SourceRange RecRange, QualType &ReturnType,
ExprValueKind &VK) {
SourceLocation SelLoc;
if (!SelectorLocs.empty() && SelectorLocs.front().isValid())
SelLoc = SelectorLocs.front();
@ -1590,8 +1613,8 @@ bool Sema::CheckMessageArgumentTypes(QualType ReceiverType,
return false;
}
ReturnType = getMessageSendResultType(ReceiverType, Method, isClassMessage,
isSuperMessage);
ReturnType = getMessageSendResultType(Receiver, ReceiverType, Method,
isClassMessage, isSuperMessage);
VK = Expr::getValueKindForType(Method->getReturnType());
unsigned NumNamedArgs = Sel.getNumArgs();
@ -2482,12 +2505,10 @@ ExprResult Sema::BuildClassMessage(TypeSourceInfo *ReceiverTypeInfo,
unsigned NumArgs = ArgsIn.size();
Expr **Args = ArgsIn.data();
if (CheckMessageArgumentTypes(ReceiverType, MultiExprArg(Args, NumArgs),
Sel, SelectorLocs,
Method, true,
SuperLoc.isValid(), LBracLoc, RBracLoc,
SourceRange(),
ReturnType, VK))
if (CheckMessageArgumentTypes(/*Receiver=*/nullptr, ReceiverType,
MultiExprArg(Args, NumArgs), Sel, SelectorLocs,
Method, true, SuperLoc.isValid(), LBracLoc,
RBracLoc, SourceRange(), ReturnType, VK))
return ExprError();
if (Method && !Method->getReturnType()->isVoidType() &&
@ -2982,9 +3003,9 @@ ExprResult Sema::BuildInstanceMessage(Expr *Receiver,
ExprValueKind VK = VK_RValue;
bool ClassMessage = (ReceiverType->isObjCClassType() ||
ReceiverType->isObjCQualifiedClassType());
if (CheckMessageArgumentTypes(ReceiverType, MultiExprArg(Args, NumArgs),
Sel, SelectorLocs, Method,
ClassMessage, SuperLoc.isValid(),
if (CheckMessageArgumentTypes(Receiver, ReceiverType,
MultiExprArg(Args, NumArgs), Sel, SelectorLocs,
Method, ClassMessage, SuperLoc.isValid(),
LBracLoc, RBracLoc, RecRange, ReturnType, VK))
return ExprError();

39
clang/test/SemaObjC/multiple-method-names-in-class-self.m Normal file
View File

@ -0,0 +1,39 @@
// RUN: %clang_cc1 -Wobjc-multiple-method-names -x objective-c -verify %s
// RUN: %clang_cc1 -Wobjc-multiple-method-names -x objective-c -verify -fobjc-arc %s
// expected-no-diagnostics
@interface NSObj
+ (instancetype) alloc;
+ (_Nonnull instancetype) globalObject;
@end
@interface SelfAllocReturn: NSObj
- (instancetype)initWithFoo:(int)x;
@end
@interface SelfAllocReturn2: NSObj
- (instancetype)initWithFoo:(SelfAllocReturn *)x;
@end
@implementation SelfAllocReturn
- (instancetype)initWithFoo:(int)x {
return self;
}
+ (instancetype) thingWithFoo:(int)x {
return [[self alloc] initWithFoo: x];
}
+ (void) initGlobal {
(void)[[self globalObject] initWithFoo: 20];
}
@end