typeck.c (build_c_cast): Preserve the cast if casting to and from an Objective-C type.

[gcc/cp/ChangeLog]
2004-09-09  Ziemowit Laski  <zlaski@apple.com>

        * typeck.c (build_c_cast): Preserve the cast if casting
        to and from an Objective-C type.

From-SVN: r87277

gcc/cp/ChangeLog

 2004-09-09  Ziemowit Laski  <zlaski@apple.com>
 
+	* typeck.c (build_c_cast): Preserve the cast if casting
+	to and from an Objective-C type.
+
+2004-09-09  Ziemowit Laski  <zlaski@apple.com>
+
 	* Make-lang.in (cp/typeck.o): Depend on c-common.h.
 	* typeck.c: Include c-common.h.
 	(comptypes): For RECORD_TYPEs, call objc_comptypes() and

gcc/cp/typeck.c

@@ -4829,6 +4829,13 @@ build_c_cast (tree type, tree expr)
       return t;
     }
 
+  /* Casts to a (pointer to a) specific ObjC class (or 'id' or
+     'Class') should always be retained, because this information aids
+     in method lookup.  */
+  if (objc_is_object_ptr (type)
+      && objc_is_object_ptr (TREE_TYPE (expr)))
+    return build_nop (type, expr);
+
   /* build_c_cast puts on a NOP_EXPR to make the result not an lvalue.
      Strip such NOP_EXPRs if VALUE is being used in non-lvalue context.  */
   if (TREE_CODE (type) != REFERENCE_TYPE