c++: dependence of constrained memfn from current inst [PR105842]
Here we incorrectly deem the calls to func1, func2 and tmpl2 as
ambiguous ahead of time ultimately because we mishandle dependence
of a constrained member function from the current instantiation.
In type_dependent_expression_p, we already consider dependence of a
TEMPLATE_DECL's constraints (via uses_outer_template_parms), but
neglect to do the same for a FUNCTION_DECL (such as that for func1).
And in satisfy_declaration_constraints, we give up if _any_ template
argument is dependent, but for non-dependent member functions from
the current instantiation (such as func2 and tmpl2), we can and must
check constraints as long as the innermost arguments aren't dependent.
PR c++/105842
gcc/cp/ChangeLog:
* constraint.cc (satisfy_declaration_constraints): Refine early
exit test for argument dependence.
* cp-tree.h (uses_outer_template_parms_in_constraints): Declare.
* pt.cc (template_class_depth): Handle TI_TEMPLATE being a
FIELD_DECL.
(usse_outer_template_parms): Factor out constraint dependence
test into ...
(uses_outer_template_parms_in_constraints): ... here.
(type_dependent_expression_p): Use it for FUNCTION_DECL.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-memtmpl6.C: New test.
(cherry picked from commit
f07778f6f92111aa0abfd0f669b148a0bda537a9)