On 12/03/2012 08:27 AM, Dodji Seketeli wrote:
+ - HAS_EXPANSION_ARG_P: Set to TRUE iff at least one parameter
+ pack has got an argument that is an expansion.
The "got" is unnecessary, just "has an argument" is better.
+ Setup APS, which is an instance of an ARGUMENT_PACK_SELECT tree, so
+ that it selects the Ith element out of the argument pack ARG_PACK.
+ If the Ith element is a pack expansion, then just select its
+ pattern. Otherwise, select the whole element.
I wonder if, rather than set up a temporary pack at this point, it makes
sense to look through pack expansions when we use an
ARGUMENT_PACK_SELECT. Is there any case where we actually want an
ARGUMENT_PACK_SELECT to be an expansion?
+ /* If we have one parameter pack whose matching argument pack is
+ just what template_parm_to_arg returned when passed the
+ parameter pack, or if we only have empty arguments ... */
+ else if (arg_from_pack_level_to_prune || has_empty_arg)
+ {
+ /* ... we just return a pack expansion which pattern is PATTERN
+ into which ARGS has been substituted. */
+ *instantiation_yields_no_list_p = true;
+ }
I was thinking we wouldn't need to recognize this case specifically,
that the code following it would work the way we want. If callers get a
vector with a single pack expansion element rather than just a pack
expansion, is that a problem? Alternately, if len == 1, maybe we should
always just return the single element.
+ /* We could not find any argument packs that work, so we'll just
+ return an unsubstituted pack expansion. The caller must be
+ prepared to deal with this. */
if (len < 0)
- return error_mark_node;
+ len = 1;
Why this change? Why is returning error_mark_node no longer the right
thing to do?
Jason
