Overhaul the AST representation of Objective-C message send

expressions, to improve source-location information, clarify the
actual receiver of the message, and pave the way for proper C++
support. The ObjCMessageExpr node represents four different kinds of
message sends in a single AST node:

  1) Send to a object instance described by an expression (e.g., [x method:5])
  2) Send to a class described by the class name (e.g., [NSString method:5])
  3) Send to a superclass class (e.g, [super method:5] in class method)
  4) Send to a superclass instance (e.g., [super method:5] in instance method)

Previously these four cases where tangled together. Now, they have
more distinct representations. Specific changes:

  1) Unchanged; the object instance is represented by an Expr*.

  2) Previously stored the ObjCInterfaceDecl* referring to the class
  receiving the message. Now stores a TypeSourceInfo* so that we know
  how the class was spelled. This both maintains typedef information
  and opens the door for more complicated C++ types (e.g., dependent
  types). There was an alternative, unused representation of these
  sends by naming the class via an IdentifierInfo *. In practice, we
  either had an ObjCInterfaceDecl *, from which we would get the
  IdentifierInfo *, or we fell into the case below...

  3) Previously represented by a class message whose IdentifierInfo *
  referred to "super". Sema and CodeGen would use isStr("super") to
  determine if they had a send to super. Now represented as a
  "class super" send, where we have both the location of the "super"
  keyword and the ObjCInterfaceDecl* of the superclass we're
  targetting (statically).

  4) Previously represented by an instance message whose receiver is a
  an ObjCSuperExpr, which Sema and CodeGen would check for via
  isa<ObjCSuperExpr>(). Now represented as an "instance super" send,
  where we have both the location of the "super" keyword and the
  ObjCInterfaceDecl* of the superclass we're targetting
  (statically). Note that ObjCSuperExpr only has one remaining use in
  the AST, which is for "super.prop" references.

The new representation of ObjCMessageExpr is 2 pointers smaller than
the old one, since it combines more storage. It also eliminates a leak
when we loaded message-send expressions from a precompiled header. The
representation also feels much cleaner to me; comments welcome!

This patch attempts to maintain the same semantics we previously had
with Objective-C message sends. In several places, there are massive
changes that boil down to simply replacing a nested-if structure such
as:

  if (message has a receiver expression) {
    // instance message
    if (isa<ObjCSuperExpr>(...)) {
     // send to super
    } else {
     // send to an object
   }
  } else {
    // class message
    if (name->isStr("super")) {
      // class send to super
    } else {
      // send to class
    }
  }

with a switch

  switch (E->getReceiverKind()) {
  case ObjCMessageExpr::SuperInstance: ...
  case ObjCMessageExpr::Instance: ...
  case ObjCMessageExpr::SuperClass: ...
  case ObjCMessageExpr::Class:...
  }

There are quite a few places (particularly in the checkers) where
send-to-super is effectively ignored. I've placed FIXMEs in most of
them, and attempted to address send-to-super in a reasonable way. This
could use some review.

llvm-svn: 101972

1 files changed, 15 insertions, 3 deletions

diff --git a/clang/lib/AST/StmtPrinter.cpp b/clang/lib/AST/StmtPrinter.cpp
index 44d475853d1..a895b63a79c 100644
--- a/clang/lib/AST/StmtPrinter.cpp
+++ b/clang/lib/AST/StmtPrinter.cpp
@@ -1247,9 +1247,21 @@ void StmtPrinter::VisitObjCProtocolExpr(ObjCProtocolExpr *Node) {
 
 void StmtPrinter::VisitObjCMessageExpr(ObjCMessageExpr *Mess) {
   OS << "[";
-  Expr *receiver = Mess->getReceiver();
-  if (receiver) PrintExpr(receiver);
-  else OS << Mess->getClassName()->getName();
+  switch (Mess->getReceiverKind()) {
+  case ObjCMessageExpr::Instance:
+    PrintExpr(Mess->getInstanceReceiver());
+    break;
+
+  case ObjCMessageExpr::Class:
+    OS << Mess->getClassReceiver().getAsString(Policy);
+    break;
+
+  case ObjCMessageExpr::SuperInstance:
+  case ObjCMessageExpr::SuperClass:
+    OS << "Super";
+    break;
+  }
+
   OS << ' ';
   Selector selector = Mess->getSelector();
   if (selector.isUnarySelector()) {