Re: [C++0x] Range-based for statements and ADL

[Jason Merrill <jason at redhat dot com>]

On 03/28/2011 08:28 PM, Rodrigo Rivas wrote:
> A few comments:
> 1. I'm not sure about what should happen if the begin/end found in class
> scope are not ordinary functions.

Whatever range.begin() would mean if written explicitly.

> My guess is that if it is a function
> (static or non-static) it is called normally, and if it is a member
> variable it is searched for an operator()(). If it is a type it should
> fail.

Yes, because we can't use . syntax to name type members.

> +	      error ("range-based-for expression must be of a complete type");

I like your "range-based %<for%>" suggestion.  I'd also say "must have 
complete type".

>   static void
>   cp_parser_perform_range_for_lookup (tree range, tree *begin, tree *end)

This function needs a comment.

> +  *end = finish_class_member_access_expr(range, *end,
> +                                        false, tf_none);
> +
> +  VEC(tree,gc) *vec;
> +  vec = make_tree_vector ();

The declaration of vec needs to move to the top of the function.

> +  id_begin = get_identifier ("begin");
> +  *begin = build_qualified_name (/*type=*/NULL_TREE,
> +                                    TREE_TYPE (range),
> +                                    id_begin,
> +                                    /*template_p=*/false);
> +  *begin = finish_class_member_access_expr(range, *begin,
> +                                              false, tf_none);
> +
> +  id_end = get_identifier ("end");
> +  *end = build_qualified_name (/*type=*/NULL_TREE,
> +                              TREE_TYPE (range),
> +                              id_end,
> +                              /*template_p=*/false);
> +  *end = finish_class_member_access_expr(range, *end,
> +                                        false, tf_none);

Don't call build_qualified_name here; the standard doesn't say 
range.T::begin(), just range.begin().

Also, we can't just call finish_class_member_access_expr here because it 
returns error_mark_node for any error condition, so we can't tell the 
difference between a lookup that didn't find anything (in which case we 
want to fall back to ADL) and an access violation (in which case we want 
to give an error).

We need to do the lookup directly first, and then do 
finish_class_member_access_expr after we've decided to use the members.

Jason