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?
{
- templ = finish_template_variable (templ, complain);
- mark_used (templ);
+ var = finish_template_variable (var, complain);
+ mark_used (var);
}
- return convert_from_reference (templ);
+ return convert_from_reference (var);
}
/* If the set of template parameters PARMS contains a template parameter
@@ -17282,7 +17283,8 @@ tsubst_copy (tree t, tree args, tsubst_flags_t
complain, tree in_decl)
TEMPLATE_DECL with `D<T>' as its DECL_CONTEXT. Now we
have to substitute this with one having context `D<int>'. */
- tree context = tsubst (DECL_CONTEXT (t), args, complain, in_decl);
+ tree context = tsubst_aggr_type (DECL_CONTEXT (t), args, complain,
+ in_decl, /*entering_scope=*/true);
return lookup_field (context, DECL_NAME(t), 0, false);
}
else
This hunk is OK.
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-friend10.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-friend10.C
new file mode 100644
index 00000000000..4b21a379f59
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-friend10.C
@@ -0,0 +1,21 @@
+// { dg-do compile { target c++20 } }
+// Verify we don't crash during constraint matching containing
+// a TEMPLATE_ID_EXPR referring to a template from the current
+// instantiation.
+
+template<class T>
+struct A {
+ template<int N> static constexpr bool C = sizeof(T) > N;
+ friend constexpr void f(A) requires C<3> { }
+ friend constexpr void f(A) requires C<3> || true { }
+};
+
+template<class T>
+struct A<T*> {
+ template<int N> static constexpr bool C = sizeof(T) > N;
+ friend constexpr void g(A) requires C<3> { }
+ friend constexpr void g(A) requires C<3> || true { }
+};
+
+template struct A<int>;
+template struct A<int*>;
