std::pair<level, justification> substitution::instantiate_metavars(level const & l, bool use_jst) {
if (!has_meta(l))
return mk_pair(l, justification());
justification j;
auto save_jst = [&](justification const & j2) { j = mk_composite1(j, j2); };
level r = replace(l, [&](level const & l) {
if (!has_meta(l)) {
return some_level(l);
} else if (is_meta(l)) {
auto p1 = get_assignment(l);
if (p1) {
auto p2 = instantiate_metavars(p1->first, use_jst);
if (use_jst) {
justification new_jst = mk_composite1(p1->second, p2.second);
assign(meta_id(l), p2.first, new_jst);
save_jst(new_jst);
} else {
assign(meta_id(l), p2.first);
}
return some_level(p2.first);
}
}
return none_level();
});
return mk_pair(r, j);
}
virtual expr visit_meta(expr const & m) {
name const & m_name = mlocal_name(m);
auto p1 = m_subst.get_expr_assignment(m_name);
if (p1) {
if (!has_metavar(p1->first)) {
if (m_use_jst)
save_jst(p1->second);
return p1->first;
} else if (m_use_jst) {
auto p2 = m_subst.instantiate_metavars(p1->first);
justification new_jst = mk_composite1(p1->second, p2.second);
m_subst.assign(m_name, p2.first, new_jst);
save_jst(new_jst);
return p2.first;
} else {
auto p2 = m_subst.instantiate_metavars(p1->first);
m_subst.assign(m_name, p2.first, mk_composite1(p1->second, p2.second));
return p2.first;
}
} else {
return m;
}
}
void save_jst(justification const & j) { m_jst = mk_composite1(m_jst, j); }
constraint mk_class_instance_root_cnstr(std::shared_ptr<class_instance_context> const & C, local_context const & _ctx,
expr const & m, bool is_strict, unifier_config const & cfg, delay_factor const & factor) {
environment const & env = C->env();
justification j = mk_failed_to_synthesize_jst(env, m);
auto choice_fn = [=](expr const & meta, expr const & meta_type, substitution const & s,
name_generator const & ngen) {
environment const & env = C->env();
auto cls_name_it = is_ext_class(C->tc(), meta_type);
if (!cls_name_it) {
// do nothing, since type is not a class.
return lazy_list<constraints>(constraints());
}
local_context ctx = _ctx.instantiate(substitution(s));
pair<expr, justification> mj = update_meta(meta, s);
expr new_meta = mj.first;
justification new_j = mj.second;
unsigned depth = 0;
constraint c = mk_class_instance_cnstr(C, ctx, new_meta, depth);
unifier_config new_cfg(cfg);
new_cfg.m_discard = false;
new_cfg.m_use_exceptions = false;
new_cfg.m_pattern = true;
new_cfg.m_kind = C->m_conservative ? unifier_kind::VeryConservative : unifier_kind::Liberal;
auto to_cnstrs_fn = [=](substitution const & subst, constraints const & cnstrs) -> constraints {
substitution new_s = subst;
// some constraints may have been postponed (example: universe level constraints)
constraints postponed = map(cnstrs,
[&](constraint const & c) {
// we erase internal justifications
return update_justification(c, mk_composite1(j, new_j));
});
metavar_closure cls(new_meta);
cls.add(meta_type);
bool relax = C->m_relax;
constraints cs = cls.mk_constraints(new_s, new_j, relax);
return append(cs, postponed);
};
auto no_solution_fn = [=]() {
if (is_strict)
return lazy_list<constraints>();
else
return lazy_list<constraints>(constraints());
};
unify_result_seq seq1 = unify(env, 1, &c, ngen, substitution(), new_cfg);
unify_result_seq seq2 = filter(seq1, [=](pair<substitution, constraints> const & p) {
substitution new_s = p.first;
expr result = new_s.instantiate(new_meta);
// We only keep complete solutions (modulo universe metavariables)
return !has_expr_metavar_relaxed(result);
});
if (get_class_unique_class_instances(C->m_ios.get_options())) {
optional<expr> solution;
substitution subst;
constraints cnstrs;
for_each(seq2, [&](pair<substitution, constraints> const & p) {
subst = p.first;
cnstrs = p.second;
expr next_solution = subst.instantiate(new_meta);
if (solution) {
throw_class_exception(m, [=](formatter const & fmt) {
format r = format("ambiguous class-instance resolution, "
"there is more than one solution");
r += pp_indent_expr(fmt, *solution);
r += compose(line(), format("and"));
r += pp_indent_expr(fmt, next_solution);
return r;
});
} else {
solution = next_solution;
}
});
if (!solution) {
return no_solution_fn();
} else {
// some constraints may have been postponed (example: universe level constraints)
return lazy_list<constraints>(to_cnstrs_fn(subst, cnstrs));
}
} else {
if (try_multiple_instances(env, *cls_name_it)) {
lazy_list<constraints> seq3 = map2<constraints>(seq2, [=](pair<substitution, constraints> const & p) {
return to_cnstrs_fn(p.first, p.second);
});
if (is_strict) {
return seq3;
} else {
// make sure it does not fail by appending empty set of constraints
return append(seq3, lazy_list<constraints>(constraints()));
}
} else {
auto p = seq2.pull();
if (!p)
return no_solution_fn();
else
return lazy_list<constraints>(to_cnstrs_fn(p->first.first, p->first.second));
}
}
};
bool owner = false;
bool relax = C->m_relax;
return mk_choice_cnstr(m, choice_fn, factor, owner, j, relax);
}