From fec112d50e801ea624900de5efd4bfd210ce53a4 Mon Sep 17 00:00:00 2001
From: John McCall <rjmccall@apple.com>
Date: Fri, 9 Sep 2011 06:11:02 +0000
Subject: [PATCH] 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.

llvm-svn: 139354
---
 clang/include/clang/Sema/Sema.h |  2 +-
 clang/lib/Sema/SemaExprObjC.cpp |  9 ++---
 clang/lib/Sema/SemaOverload.cpp | 64 ++++++++++++++++++++++++---------
 3 files changed, 51 insertions(+), 24 deletions(-)

diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index ef35bc161066..4bdf3802aabd 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/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,
diff --git a/clang/lib/Sema/SemaExprObjC.cpp b/clang/lib/Sema/SemaExprObjC.cpp
index f6ace99bf6c0..f7f00f3f91b3 100644
--- a/clang/lib/Sema/SemaExprObjC.cpp
+++ b/clang/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,
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index c0b83d9b47ae..1c78b3d11381 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/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'.
-static ImplicitConversionSequence
-TryContextuallyConvertToObjCId(Sema &S, Expr *From) {
-  QualType Ty = S.Context.getObjCIdType();
-  return TryImplicitConversion(S, From, Ty,
-                               // FIXME: Are these flags correct?
-                               /*SuppressUserConversions=*/false,
-                               /*AllowExplicit=*/true,
-                               /*InOverloadResolution=*/false,
-                               /*CStyle=*/false,
-                               /*AllowObjCWritebackConversion=*/false);
+/// 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];
+  }
 }
 
-/// PerformContextuallyConvertToObjCId - Perform a contextual conversion
-/// of the expression From to 'id'.
-ExprResult Sema::PerformContextuallyConvertToObjCId(Expr *From) {
+/// TryContextuallyConvertToObjCPointer - Attempt to contextually
+/// convert the expression From to an Objective-C pointer type.
+static ImplicitConversionSequence
+TryContextuallyConvertToObjCPointer(Sema &S, Expr *From) {
+  // Do an implicit conversion to 'id'.
+  QualType Ty = S.Context.getObjCIdType();
+  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;
+  }
+
+  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();