Contextually converting to 'id' is not a useful operation. Contextually

converting to an arbitrary Objective-C pointer type is.  Without
significantly re-implementing anything, change the API to reflect this,
and as a minor optimization, strip the pointer conversion off before
potentially building it.

Mostly, this removes a really bizarre-looking bit of code from
BuildInstanceMessage.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@139354 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Sema/Sema.h

@@ -1387,7 +1387,7 @@ public:
                                                  CXXMethodDecl *Method);
 
   ExprResult PerformContextuallyConvertToBool(Expr *From);
-  ExprResult PerformContextuallyConvertToObjCId(Expr *From);
+  ExprResult PerformContextuallyConvertToObjCPointer(Expr *From);
 
   ExprResult 
   ConvertToIntegralOrEnumerationType(SourceLocation Loc, Expr *FromE,

lib/Sema/SemaExprObjC.cpp

@@ -1366,17 +1366,12 @@ ExprResult Sema::BuildInstanceMessage(Expr *Receiver,
                             IsNull ? CK_NullToPointer : CK_IntegralToPointer).take();
         }
         ReceiverType = Receiver->getType();
-      } 
-      else {
+      } else {
         ExprResult ReceiverRes;
         if (getLangOptions().CPlusPlus)
-          ReceiverRes = PerformContextuallyConvertToObjCId(Receiver);
+          ReceiverRes = PerformContextuallyConvertToObjCPointer(Receiver);
         if (ReceiverRes.isUsable()) {
           Receiver = ReceiverRes.take();
-          if (ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(Receiver)) {
-            Receiver = ICE->getSubExpr();
-            ReceiverType = Receiver->getType();
-          }
           return BuildInstanceMessage(Receiver,
                                       ReceiverType,
                                       SuperLoc,

lib/Sema/SemaOverload.cpp

@@ -3868,25 +3868,57 @@ ExprResult Sema::PerformContextuallyConvertToBool(Expr *From) {
   return ExprError();
 }
 
-/// TryContextuallyConvertToObjCId - Attempt to contextually convert the
-/// expression From to 'id'.
+/// dropPointerConversions - If the given standard conversion sequence
+/// involves any pointer conversions, remove them.  This may change
+/// the result type of the conversion sequence.
+static void dropPointerConversion(StandardConversionSequence &SCS) {
+  if (SCS.Second == ICK_Pointer_Conversion) {
+    SCS.Second = ICK_Identity;
+    SCS.Third = ICK_Identity;
+    SCS.ToTypePtrs[2] = SCS.ToTypePtrs[1] = SCS.ToTypePtrs[0];
+  }
+}
+
+/// TryContextuallyConvertToObjCPointer - Attempt to contextually
+/// convert the expression From to an Objective-C pointer type.
 static ImplicitConversionSequence
-TryContextuallyConvertToObjCId(Sema &S, Expr *From) {
+TryContextuallyConvertToObjCPointer(Sema &S, Expr *From) {
+  // Do an implicit conversion to 'id'.
   QualType Ty = S.Context.getObjCIdType();
-  return TryImplicitConversion(S, From, Ty,
+  ImplicitConversionSequence ICS
+    = TryImplicitConversion(S, From, Ty,
                             // FIXME: Are these flags correct?
                             /*SuppressUserConversions=*/false,
                             /*AllowExplicit=*/true,
                             /*InOverloadResolution=*/false,
                             /*CStyle=*/false,
                             /*AllowObjCWritebackConversion=*/false);
+
+  // Strip off any final conversions to 'id'.
+  switch (ICS.getKind()) {
+  case ImplicitConversionSequence::BadConversion:
+  case ImplicitConversionSequence::AmbiguousConversion:
+  case ImplicitConversionSequence::EllipsisConversion:
+    break;
+
+  case ImplicitConversionSequence::UserDefinedConversion:
+    dropPointerConversion(ICS.UserDefined.After);
+    break;
+
+  case ImplicitConversionSequence::StandardConversion:
+    dropPointerConversion(ICS.Standard);
+    break;
   }
 
-/// PerformContextuallyConvertToObjCId - Perform a contextual conversion
-/// of the expression From to 'id'.
-ExprResult Sema::PerformContextuallyConvertToObjCId(Expr *From) {
+  return ICS;
+}
+
+/// PerformContextuallyConvertToObjCPointer - Perform a contextual
+/// conversion of the expression From to an Objective-C pointer type.
+ExprResult Sema::PerformContextuallyConvertToObjCPointer(Expr *From) {
   QualType Ty = Context.getObjCIdType();
-  ImplicitConversionSequence ICS = TryContextuallyConvertToObjCId(*this, From);
+  ImplicitConversionSequence ICS =
+    TryContextuallyConvertToObjCPointer(*this, From);
   if (!ICS.isBad())
     return PerformImplicitConversion(From, Ty, ICS, AA_Converting);
   return ExprError();