PATCH: Fix ObjC protocol qualification lossage (Take 2)

[Ziemowit Laski <zlaski at apple dot com>]

(Renamed is_id to objc_is_id, per Neil's suggestion)

The following patch addresses a bug whereby the protocol
qualifications of ObjC objects were sometimes forgotten,
leading to erroneous warning messages.  This issue was raised
on the gcc list a few days ago, and I believe it to be a regression
from 2.95.x.

Bootstrapped on i686-pc-linux-gnu with no regressions, plus there
is a test case.  OK?

[gcc/ChangeLog]
2002-09-06  Ziemowit Laski <zlaski@apple.com>

        * c-lang.c (objc_is_id): New stub.
        * c-tree.h (objc_is_id): New forward declaration.
        * c-typeck.c (build_c_cast): Do not strip protocol
        qualifiers from 'id' type.
        * objc/objc-act.c (objc_comptypes): Correct handling
        of protocol qualifiers.
        (objc_is_id): New.

[gcc/testsuite/ChangeLog]
2002-09-05  Ziemowit Laski <zlaski@apple.com>

        * objc.dg/proto-lossage-1.m: New test.


Index: gcc/c-lang.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/c-lang.c,v
retrieving revision 1.99
diff -c -3 -p -r1.99 c-lang.c
*** gcc/c-lang.c        3 Sep 2002 16:40:29 -0000       1.99
--- gcc/c-lang.c        6 Sep 2002 19:14:12 -0000
*************** is_class_name (arg)
*** 174,179 ****
--- 174,186 ----
    return 0;
  }

+ tree
+ objc_is_id (arg)
+     tree arg ATTRIBUTE_UNUSED;
+ {
+   return 0;
+ }
+
  void
  objc_check_decl (decl)
       tree decl ATTRIBUTE_UNUSED;
Index: gcc/c-tree.h
===================================================================
RCS file: /cvs/gcc/gcc/gcc/c-tree.h,v
retrieving revision 1.106
diff -c -3 -p -r1.106 c-tree.h
*** gcc/c-tree.h        3 Sep 2002 16:40:29 -0000       1.106
--- gcc/c-tree.h        6 Sep 2002 19:14:12 -0000
*************** struct lang_type GTY(())
*** 165,170 ****
--- 165,171 ----
  /* in c-lang.c and objc-act.c */
  extern tree lookup_interface                  PARAMS ((tree));
  extern tree is_class_name                     PARAMS ((tree));
+ extern tree objc_is_id                        PARAMS ((tree));
  extern void objc_check_decl                   PARAMS ((tree));
  extern void finish_file                               PARAMS ((void));
  extern int objc_comptypes                     PARAMS ((tree, tree, 
int));
Index: gcc/c-typeck.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/c-typeck.c,v
retrieving revision 1.204
diff -c -3 -p -r1.204 c-typeck.c
*** gcc/c-typeck.c      3 Sep 2002 16:40:29 -0000       1.204
--- gcc/c-typeck.c      6 Sep 2002 19:14:22 -0000
*************** build_c_cast (type, expr)
*** 3577,3583 ****

    if (type == error_mark_node || expr == error_mark_node)
      return error_mark_node;
!   type = TYPE_MAIN_VARIANT (type);

  #if 0
    /* Strip NON_LVALUE_EXPRs since we aren't using as an lvalue.  */
--- 3577,3588 ----

    if (type == error_mark_node || expr == error_mark_node)
      return error_mark_node;
!
!   /* The ObjC front-end uses TYPE_MAIN_VARIANT to tie together types 
differing
!      only in <protocol> qualifications.  But when constructing cast 
expressions,
!      the protocols do matter and must be kept around.  */
!   if (!flag_objc || !objc_is_id (type))
!     type = TYPE_MAIN_VARIANT (type);

  #if 0
    /* Strip NON_LVALUE_EXPRs since we aren't using as an lvalue.  */
Index: gcc/objc/objc-act.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/objc/objc-act.c,v
retrieving revision 1.155
diff -c -3 -p -r1.155 objc-act.c
*** gcc/objc/objc-act.c 3 Sep 2002 10:39:40 -0000       1.155
--- gcc/objc/objc-act.c 6 Sep 2002 19:14:23 -0000
*************** objc_comptypes (lhs, rhs, reflexive)
*** 648,660 ****
                      tree cat;

                      rproto_list = CLASS_PROTOCOL_LIST (rinter);
-                     /* If the underlying ObjC class does not have
-                        protocols attached to it, perhaps there are
-                        "one-off" protocols attached to the rhs?
-                        E.g., 'id<MyProt> foo;'.  */
-                     if (!rproto_list)
-                       rproto_list = TYPE_PROTOCOL_LIST (TREE_TYPE 
(rhs));
                      rproto = lookup_protocol_in_reflist (rproto_list, 
p);

                      /* Check for protocols adopted by categories.  */
                      cat = CLASS_CATEGORY_LIST (rinter);
--- 648,663 ----
                      tree cat;

                      rproto_list = CLASS_PROTOCOL_LIST (rinter);
                      rproto = lookup_protocol_in_reflist (rproto_list, 
p);
+                     /* If the underlying ObjC class does not have
+                        the protocol we're looking for, check for 
"one-off"
+                        protocols (e.g., `NSObject<MyProt> foo;') 
attached
+                        to the rhs.  */
+                     if (!rproto)
+                       {
+                         rproto_list = TYPE_PROTOCOL_LIST (TREE_TYPE 
(rhs));
+                         rproto = lookup_protocol_in_reflist 
(rproto_list, p);
+                       }

                      /* Check for protocols adopted by categories.  */
                      cat = CLASS_CATEGORY_LIST (rinter);
*************** is_class_name (ident)
*** 2259,2264 ****
--- 2262,2278 ----
      }

    return 0;
+ }
+
+ tree
+ objc_is_id (ident)
+      tree ident;
+ {
+   /* NB: This function may be called before the ObjC front-end
+      has been initialized, in which case ID_TYPE will be NULL. */
+   return (id_type && ident && TYPE_P (ident) && IS_ID (ident))
+         ? id_type
+         : NULL_TREE;
  }
Index: gcc/testsuite/objc.dg/proto-lossage-1.m
===================================================================
RCS file: gcc/testsuite/objc.dg/proto-lossage-1.m
diff -N gcc/testsuite/objc.dg/proto-lossage-1.m
*** /dev/null   1 Jan 1970 00:00:00 -0000
--- gcc/testsuite/objc.dg/proto-lossage-1.m     6 Sep 2002 22:06:31 
-0000
***************
*** 0 ****
--- 1,44 ----
+ /* Test for situations in which protocol conformance information
+    may be lost, leading to superfluous warnings.  */
+ /* Author: Ziemowit Laski <zlaski@apple.com>.  */
+ /* { dg-do compile } */
+ /* { dg-options "-Werror" } */
+
+ /* One-line substitute for objc/objc.h */
+ typedef struct objc_object { struct objc_class *class_pointer; } *id;
+
+ @protocol NSObject
+ - (int)someValue;
+ @end
+
+ @interface NSObject <NSObject>
+ @end
+
+ @protocol PlateMethods
+ - (void)someMethod;
+ @end
+
+ @interface Foo {
+   NSObject <PlateMethods> *plate;
+   id <PlateMethods> plate1;
+   NSObject *plate2;
+ }
+ - (id <PlateMethods>) getPlate;
+ - (id <NSObject>) getPlate1;
+ - (int) getValue;
+ @end
+
+ @implementation Foo
+ - (id <PlateMethods>) getPlate {
+   return plate;  /* { dg-bogus "does not implement" } */
+ }
+ - (id <NSObject>) getPlate1 {
+   return (id <NSObject>)plate1; /* { dg-bogus "does not conform" } */
+ }
+ - (int) getValue {
+   int i = [plate1 someValue];   /* { dg-warning "not implemented by 
protocol" } */
+   int j = [(id <NSObject>)plate1 someValue];  /* { dg-bogus "not 
implemented by protocol" } */
+   int k = [(id)plate1 someValue]; /* { dg-bogus "not implemented by 
protocol" } */
+   return i + j + k;
+ }
+ @end


--------------------------------------------------------------
Ziemowit Laski                 1 Infinite Loop, MS 301-2K
Mac OS X Compiler Group        Cupertino, CA USA  95014-2083
Apple Computer, Inc.           +1.408.974.6229  Fax .5477