On Tue, Jan 19, 2016 at 9:56 AM, Jason Merrill <ja...@redhat.com> wrote:
> On 01/18/2016 10:55 PM, Patrick Palka wrote:
>>
>> mark_used is wrongly diagnosing a use of a TEMPLATE_DECL (e.g. the call
>> to f1 in function f3 of auto-fn29.C below) for having an undeduced
>> 'auto' return type. This doesn't make sense, because an 'auto' used
>> inside a template doesn't get deduced until after the template is
>> instantiated. So for a TEMPLATE_DECL we shouldn't diagnose a use of
>> undeduced 'auto' here. After instantiation, presumably we will call
>> mark_used on the resulting FUNCTION_DECL which will check for undeduced
>> auto appropriately.
>> @@ -5112,7 +5112,9 @@ mark_used (tree decl, tsubst_flags_t complain)
>> || DECL_LANG_SPECIFIC (decl) == NULL
>> || DECL_THUNK_P (decl))
>> {
>> - if (!processing_template_decl && type_uses_auto (TREE_TYPE (decl)))
>> + if (!processing_template_decl
>> + && TREE_CODE (decl) != TEMPLATE_DECL
>> + && type_uses_auto (TREE_TYPE (decl)))
>
>
> How does a TEMPLATE_DECL get in here? Does it have null DECL_LANG_SPECIFIC?
(In the test case auto-fn29.C,) When instantiating the template
function f3,we call tsubst on the CALL_EXPR "f1 (v);". There, ADL is
performed on the identifier f1 (which is the CALL_EXPR_FN) which
returns the TEMPLATE_DECL f1. Then mark_used is called on this
CALL_EXPR_FN, only if it's a decl.
If in the test case the call to "f1 (v);" is replaced with "Ape::f1
(v);" then the CALL_EXPR_FN is then an OVERLOAD (to the TEMPLATE_DECL
f1), i.e. not a decl, so we don't call mark_used on it in tsubst.
The DECL_LANG_SPECIFIC of this decl is not null.
>
> I'd think mark_used of a TEMPLATE_DECL should return after setting
> TREE_USED, there's nothing else to do with it.
Consider it changed.
>
> Jason
>
>
