That looks good, OK.
On Mon, Sep 19, 2016 at 11:17 AM, Patrick Palka <patr...@parcs.ath.cx> wrote:
> On Mon, 19 Sep 2016, Jason Merrill wrote:
>
>> > if (tree t = maybe_new_partial_specialization (type))
>> > {
>> > + if (processing_template_parmlist)
>> > + {
>> > + /* Some syntactically invalid code can confuse the compiler
>> > into
>> > + defining a specialization from inside a template parameter
>> > + list. Bail out now so that we won't ICE later. */
>> > + gcc_assert (seen_error ());
>> > + return error_mark_node;
>> > + }
>>
>> Rather than decide it's a specialization and then fail, let's avoid
>> treating it as a specialization in the first place. I think we can
>> add a processing_template_parmlist check at the top where we avoid
>> trying to specialize lambdas.
>>
>> Jason
>>
>
> This works too. However I was playing around with the parser a bit and
> noticed that the following also fixes the ICE. It makes no sense to try
> to recover gracefully from a presumed missing "template <>" prefix when
> processing_template_parmlist. This is what seems to be responsible for
> creating the bogus specialization. Does this look OK or do you prefer
> adjusting maybe_process_partial_specialization()?
>
> gcc/cp/ChangeLog:
>
> PR c++/77639
> * parser.c (cp_parser_class_head): When
> processing_template_parmlist, don't assume that a
> class-head starts an explicit specialization.
>
> gcc/testsuite/ChangeLog:
>
> PR c++/77639
> * g++.dg/template/error-recovery4.C: New test.
> ---
> gcc/cp/parser.c | 1 +
> gcc/testsuite/g++.dg/template/error-recovery4.C | 5 +++++
> 2 files changed, 6 insertions(+)
> create mode 100644 gcc/testsuite/g++.dg/template/error-recovery4.C
>
> diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
> index fb88021..c03b9c2 100644
> --- a/gcc/cp/parser.c
> +++ b/gcc/cp/parser.c
> @@ -22025,6 +22025,7 @@ cp_parser_class_head (cp_parser* parser,
> it is not, try to recover gracefully. */
> if (at_namespace_scope_p ()
> && parser->num_template_parameter_lists == 0
> + && !processing_template_parmlist
> && template_id_p)
> {
> /* Build a location of this form:
> diff --git a/gcc/testsuite/g++.dg/template/error-recovery4.C
> b/gcc/testsuite/g++.dg/template/error-recovery4.C
> new file mode 100644
> index 0000000..1e52c6a
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/template/error-recovery4.C
> @@ -0,0 +1,5 @@
> +// PR c++/77639
> +
> +template <class, int, class, int> struct B {};
> +template <class T, int a, class U struct B<T, a, U, 1> {}; // { dg-error "" }
> +B<int, 2, char, 1> i;
> --
> 2.10.0.87.g1cd26dd
>
