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[c++-concepts] Class template constraints


Attached is a patch for constrained class templates. It's the 3rd time
I've sent it.

I added some fixes for bugs discovered after the previous send, and
added support for matching constrained declarations in out-of-class
member function definitions.

2013-08-02  Andrew Sutton  <andrew.n.sutton@gmail.com>
        * gcc/cp/pt.c (get_class_bindings): Pass the partial specialization
        for constraint evaluation. Evaluate constraints, resulting in
        deduction failure on error.
        (get_specializaing_template_decl), (get_specialization_constraints),
        (maybe_new_partial_specialization): New.
        (maybe_process_partial_specialization): Allow the creation of
        new types for constrained partial specializations.
        (process_partial_specialization): Modify the canonical type
        of constrained partial specializations.
        (resolve_template_scope): New. Match the template scope to a
        specialization with appropriate constraints.
        (lookup_template_class_1): Compare constraints when entering a
        template scope. Check constraints on lookup. Do not explicitly check
        alias constraints.
        (instantiate_class_template_1): Do not explicitly check constraints
        during class template instantiation.
        (tsubst_decl): Instantiate the constraints of template declarations.
        (more_specialized_class): Pass specializations to get_class_bindings().
        Compare specialization constraints if the types are equivalent.
        (most_specialized_class): Pass specialization to get_class_bndings().
        * gcc/cp/decl2.c (check_class_fn): Get the decl's requirements from
        either the current template reqs or from the template parameters.
        Allow overloading of constrained out-of-class member definitions.
        * gcc/cp/parser.c (cp_parser_parse_type_parameter): Attach
        requirements to the current template parameter list.
        (cp_parser_init_declarator): Parse requires clauses for out-of-class
        member definitions. Be sure to restore current constraints before
        exiting the function.
        (cp_parser_member_declarator): Restore the previous requirements in
        an early-exit branch.
        (cp_parser_late_parsing_for_member): Restore constraints after
        maybe_end_member_template_processing().
        (cp_parser_template_declaration_after_exp): Attach constraints to
        the current template parameters.
        * gcc/cp/constraint.cc (reduce_template_id): Don't crash when
        omitting ()'s on constraint calls.
        (check_requirements): Don't evaluate dependent arguments.
        (check_constraints): Don't try to evaluate when arguments are
        dependent.
        (equivalent_constraints): Optimize the case when a and b are the
        same constraints.

-- 
Andrew Sutton

Attachment: template.patch
Description: Binary data


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