P08184R0: Generalizing the Range-Based For Loop

	* parser.c (cp_convert_range_for): Set the type of __end separately.
	(cp_parser_perform_range_for_lookup): Allow different begin/end
	types if they are comparable.

Co-Authored-By: Jason Merrill <jason@redhat.com>

From-SVN: r234191

gcc/cp/ChangeLog

+2016-03-14  Casey Carter  <casey@carter.net>
+	    Jason Merrill  <jason@redhat.com>
+
+	P08184R0: Generalizing the Range-Based For Loop
+	* parser.c (cp_convert_range_for): Set the type of __end separately.
+	(cp_parser_perform_range_for_lookup): Allow different begin/end
+	types if they are comparable.
+
 2016-03-12  Patrick Palka  <ppalka@gcc.gnu.org>
 
 	PR c++/70106

gcc/cp/parser.c

@@ -11353,6 +11353,8 @@ cp_convert_range_for (tree statement, tree range_decl, tree range_expr,
 		  /*is_constant_init*/false, NULL_TREE,
 		  LOOKUP_ONLYCONVERTING);
 
+  if (cxx_dialect >= cxx1z)
+    iter_type = cv_unqualified (TREE_TYPE (end_expr));
   end = build_decl (input_location, VAR_DECL,
 		    get_identifier ("__for_end"), iter_type);
   TREE_USED (end) = 1;
@@ -11488,9 +11490,21 @@ cp_parser_perform_range_for_lookup (tree range, tree *begin, tree *end)
 	  /* The unqualified type of the __begin and __end temporaries should
 	     be the same, as required by the multiple auto declaration.  */
 	  if (!same_type_p (iter_type, cv_unqualified (TREE_TYPE (*end))))
-	    error ("inconsistent begin/end types in range-based %<for%> "
-		   "statement: %qT and %qT",
-		   TREE_TYPE (*begin), TREE_TYPE (*end));
+	    {
+	      if (cxx_dialect >= cxx1z
+		  && (build_x_binary_op (input_location, NE_EXPR,
+					 *begin, ERROR_MARK,
+					 *end, ERROR_MARK,
+					 NULL, tf_none)
+		      != error_mark_node))
+		/* P08184R0 allows __begin and __end to have different types,
+		   but make sure they are comparable so we can give a better
+		   diagnostic.  */;
+	      else
+		error ("inconsistent begin/end types in range-based %<for%> "
+		       "statement: %qT and %qT",
+		       TREE_TYPE (*begin), TREE_TYPE (*end));
+	    }
 	  return iter_type;
 	}
     }

gcc/testsuite/g++.dg/cpp0x/range-for5.C

@@ -31,7 +31,7 @@ struct Explicit
 void test1()
 {
   container c;
-  for (int x : c) // { dg-error "inconsistent|conversion" }
+  for (int x : c) // { dg-error "inconsistent|conversion|comparison" }
     ;
 
   int a[2] = {1,2};

gcc/testsuite/g++.dg/cpp1z/range-for1.C

+// P08184R0: Generalizing the Range-Based For Loop
+// { dg-options "-std=c++1z" }
+
+struct A {
+  int ar[4];
+  int *begin() { return ar; }
+  struct end_t {
+    int *p;
+    friend bool operator!= (int *p, end_t e) { return p != e.p; }
+  };
+  end_t end() { return { &ar[4] }; }
+};
+
+int main()
+{
+  A a { 1, 2, 3, 4 };
+  int i = 1;
+  for (auto x: a)
+    if (x != i++)
+      __builtin_abort ();
+  if (i != 5)
+    __builtin_abort ();
+}