[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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@349841 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/clang/Sema/Sema.h b/include/clang/Sema/Sema.h
index 7685b3f74ad0be4585936a2b6958f02eefccfaa2..fd83b374ad2db8f8b0a49a0392505726bb3a17f0 100644 (file)
--- a/include/clang/Sema/Sema.h
+++ b/include/clang/Sema/Sema.h
@@ -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.

diff --git a/lib/Sema/SemaExprObjC.cpp b/lib/Sema/SemaExprObjC.cpp
index 9eaf747ae79ebed229dedc5c111ebd6a6805db34..ce80db7ca6ecef7bc107d79ce21ac8410ea667d8 100644 (file)
--- a/lib/Sema/SemaExprObjC.cpp
+++ b/lib/Sema/SemaExprObjC.cpp
@@ -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();
 

diff --git a/test/SemaObjC/multiple-method-names-in-class-self.m b/test/SemaObjC/multiple-method-names-in-class-self.m
new file mode 100644 (file)
index 0000000..47e1306
--- /dev/null
+++ b/test/SemaObjC/multiple-method-names-in-class-self.m
@@ -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