On 9/17/22 10:31, Patrick Palka wrote:
On Sat, 17 Sep 2022, Jason Merrill wrote:
On 9/16/22 10:59, Patrick Palka wrote:
On Fri, 16 Sep 2022, Jason Merrill wrote:
On 9/15/22 11:58, Patrick Palka wrote:
Here we're crashing during constraint matching for the instantiated
hidden friends due to two issues with dependent substitution into a
TEMPLATE_ID_EXPR naming a template from the current instantiation
(as performed from maybe_substitute_reqs_for for C<3> with T=T):
* tsubst_copy substitutes into such a TEMPLATE_DECL by looking it
up from the substituted class scope. But for this to not fail
when
the args are dependent, we need to pass entering_scope=true for
the
class scope substitution so that we obtain the primary template
type
A<T> (which has TYPE_BINFO) instead of the implicit instantiation
A<T> (which doesn't).
* lookup_and_finish_template_variable shouldn't instantiate a
TEMPLATE_ID_EXPR that names a TEMPLATE_DECL which has more than
one level of (unsubstituted) parameters (such as A<T>::C).
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk?
gcc/cp/ChangeLog:
* pt.cc (lookup_and_finish_template_variable): Don't
instantiate if the template's scope is dependent.
(tsubst_copy) <case TEMPLATE_DECL>: Pass entering_scope=true
when substituting the class scope.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-friend10.C: New test.
---
gcc/cp/pt.cc | 14 +++++++------
.../g++.dg/cpp2a/concepts-friend10.C | 21
+++++++++++++++++++
2 files changed, 29 insertions(+), 6 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-friend10.C
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index db4e808adec..bfcbe0b8670 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -10475,14 +10475,15 @@ tree
lookup_and_finish_template_variable (tree templ, tree targs,
tsubst_flags_t complain)
{
- templ = lookup_template_variable (templ, targs);
- if (!any_dependent_template_arguments_p (targs))
+ tree var = lookup_template_variable (templ, targs);
+ if (TMPL_PARMS_DEPTH (DECL_TEMPLATE_PARMS (templ)) == 1
+ && !any_dependent_template_arguments_p (targs))
I notice that finish_id_expression_1 uses the equivalent of
type_dependent_expression_p (var). Does that work here?
Hmm, it does, but kind of by accident: type_dependent_expression_p
returns true for all variable TEMPLATE_ID_EXPRs because of their empty
TREE_TYPE (as set by finish_template_variable). So testing t_d_e_p here
is equivalent to testing processing_template_decl, it seems -- maximally
conservative.
We can improve type_dependent_expression_p for variable TEMPLATE_ID_EXPR
by ignoring its (always empty) TREE_TYPE and just considering dependence
of its template and args directly.
I guess the problem is that a variable template specialization is
type-dependent until it's instantiated or specialized, and here we're
trying to instantiate if that hasn't happened yet, so using
type_dependent_expression_p would be wrong.
The patch is OK as is.
Jason
