262 lines
12 KiB
C++
262 lines
12 KiB
C++
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/*
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Copyright (c) 2014 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Author: Leonardo de Moura
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*/
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#include "kernel/instantiate.h"
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#include "kernel/abstract.h"
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#include "library/unifier.h"
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#include "library/opaque_hints.h"
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#include "frontends/lean/util.h"
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#include "frontends/lean/class.h"
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#include "frontends/lean/tactic_hint.h"
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#include "frontends/lean/local_context.h"
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#include "frontends/lean/choice_iterator.h"
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namespace lean {
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/** \brief Context for handling placeholder metavariable choice constraint */
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struct placeholder_context {
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io_state m_ios;
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name_generator m_ngen;
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type_checker_ptr m_tc;
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local_context m_ctx;
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bool m_relax;
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bool m_use_local_instances;
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placeholder_context(environment const & env, io_state const & ios, list<expr> const & ctx,
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name const & prefix, bool relax, bool use_local_instances):
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m_ios(ios),
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m_ngen(prefix),
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m_tc(mk_type_checker_with_hints(env, m_ngen.mk_child(), relax)),
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m_ctx(m_ngen.next(), ctx),
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m_relax(relax),
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m_use_local_instances(use_local_instances) {
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}
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environment const & env() const { return m_tc->env(); }
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io_state const & ios() const { return m_ios; }
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bool use_local_instances() const { return m_use_local_instances; }
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type_checker & tc() const { return *m_tc; }
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};
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pair<expr, constraint> mk_placeholder_elaborator(std::shared_ptr<placeholder_context> const & C,
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bool is_strict, optional<expr> const & type, tag g);
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/** \brief Whenever the elaborator finds a placeholder '_' or introduces an
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implicit argument, it creates a metavariable \c ?m. It also creates a
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delayed choice constraint (?m in fn).
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The function \c fn produces a stream of alternative solutions for ?m.
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In this case, \c fn will do the following:
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1) if the elaborated type of ?m is a 'class' C, then the stream will start with
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a) all local instances of class C (if elaborator.local_instances == true)
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b) solutions produced by tactic_hints for class C
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2) if the elaborated type of ?m is not a class, then the stream will only contain
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the solutions produced by tactic_hints.
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The unifier only process delayed choice constraints when there are no other kind
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of constraint to be processed.
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This is a helper class for implementing this choice function.
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*/
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struct placeholder_elaborator : public choice_iterator {
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std::shared_ptr<placeholder_context> m_C;
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expr m_meta;
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// elaborated type of the metavariable
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expr m_meta_type;
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// local instances that should also be included in the
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// class-instance resolution.
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// This information is retrieved from the local context
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list<expr> m_local_instances;
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// global declaration names that are class instances.
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// This information is retrieved using #get_class_instances.
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list<name> m_instances;
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// Tactic hints for the class
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list<tactic_hint_entry> m_tactics;
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// result produce by last executed tactic.
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proof_state_seq m_tactic_result;
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// metavariables that occur in m_meta_type, the tactics may instantiate some of them
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buffer<expr> m_mvars_in_meta_type;
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justification m_jst;
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placeholder_elaborator(std::shared_ptr<placeholder_context> const & C,
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expr const & meta, expr const & meta_type,
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list<expr> const & local_insts, list<name> const & instances,
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list<tactic_hint_entry> const & tacs,
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justification const & j, bool ignore_failure):
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choice_iterator(ignore_failure), m_C(C),
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m_meta(meta), m_meta_type(meta_type),
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m_local_instances(local_insts), m_instances(instances),
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m_tactics(tacs),
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m_jst(j) {
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collect_metavars(meta_type, m_mvars_in_meta_type);
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}
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constraints mk_constraints(constraint const & c, buffer<constraint> const & cs) {
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return cons(c, to_list(cs.begin(), cs.end()));
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}
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optional<constraints> try_instance(expr const & inst, expr const & inst_type) {
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type_checker & tc = m_C->tc();
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name_generator & ngen = m_C->m_ngen;
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tag g = inst.get_tag();
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local_context & ctx = m_C->m_ctx;
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try {
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local_context::scope scope(ctx);
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buffer<expr> locals;
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expr meta_type = m_meta_type;
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while (true) {
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meta_type = tc.whnf(meta_type).first;
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if (!is_pi(meta_type))
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break;
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expr local = mk_local(ngen.next(), binding_name(meta_type),
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binding_domain(meta_type), binding_info(meta_type));
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ctx.add_local(local);
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locals.push_back(local);
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meta_type = instantiate(binding_body(meta_type), local);
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}
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expr type = inst_type;
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expr r = inst;
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buffer<constraint> cs;
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while (true) {
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type = tc.whnf(type).first;
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if (!is_pi(type))
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break;
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bool is_strict = true;
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pair<expr, constraint> ac = mk_placeholder_elaborator(m_C, is_strict,
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some_expr(binding_domain(type)), g);
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expr arg = ac.first;
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cs.push_back(ac.second);
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r = mk_app(r, arg).set_tag(g);
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type = instantiate(binding_body(type), arg);
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}
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r = Fun(locals, r);
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bool relax = m_C->m_relax;
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constraint c = mk_eq_cnstr(m_meta, r, m_jst, relax);
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return optional<constraints>(mk_constraints(c, cs));
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} catch (exception &) {
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return optional<constraints>();
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}
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}
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optional<constraints> try_instance(name const & inst) {
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environment const & env = m_C->env();
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if (auto decl = env.find(inst)) {
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name_generator & ngen = m_C->m_ngen;
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buffer<level> ls_buffer;
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unsigned num_univ_ps = length(decl->get_univ_params());
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for (unsigned i = 0; i < num_univ_ps; i++)
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ls_buffer.push_back(mk_meta_univ(ngen.next()));
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levels ls = to_list(ls_buffer.begin(), ls_buffer.end());
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expr inst_cnst = copy_tag(m_meta, mk_constant(inst, ls));
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expr inst_type = instantiate_type_univ_params(*decl, ls);
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return try_instance(inst_cnst, inst_type);
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} else {
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return optional<constraints>();
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}
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}
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optional<constraints> get_next_tactic_result() {
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while (auto next = m_tactic_result.pull()) {
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m_tactic_result = next->second;
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if (!empty(next->first.get_goals()))
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continue; // has unsolved goals
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substitution subst = next->first.get_subst();
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buffer<constraint> cs;
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expr const & mvar = get_app_fn(m_meta);
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bool relax = m_C->m_relax;
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cs.push_back(mk_eq_cnstr(mvar, subst.instantiate(mvar), m_jst, relax));
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for (auto const & mvar : m_mvars_in_meta_type)
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cs.push_back(mk_eq_cnstr(mvar, subst.instantiate(mvar), m_jst, relax));
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return optional<constraints>(to_list(cs.begin(), cs.end()));
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}
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return optional<constraints>();
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}
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virtual optional<constraints> next() {
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while (!empty(m_local_instances)) {
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expr inst = head(m_local_instances);
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m_local_instances = tail(m_local_instances);
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if (!is_local(inst))
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continue;
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if (auto r = try_instance(inst, mlocal_type(inst)))
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return r;
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}
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while (!empty(m_instances)) {
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name inst = head(m_instances);
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m_instances = tail(m_instances);
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if (auto cs = try_instance(inst))
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return cs;
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}
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if (auto cs = get_next_tactic_result())
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return cs;
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while (!empty(m_tactics)) {
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tactic const & tac = head(m_tactics).get_tactic();
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m_tactics = tail(m_tactics);
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proof_state ps(goals(goal(m_meta, m_meta_type)), substitution(), m_C->m_ngen.mk_child());
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try {
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m_tactic_result = tac(m_C->env(), m_C->ios(), ps);
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if (auto cs = get_next_tactic_result())
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return cs;
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} catch (exception &) {}
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}
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return optional<constraints>();
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}
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};
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pair<expr, constraint> mk_placeholder_elaborator(std::shared_ptr<placeholder_context> const & C,
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bool is_strict, optional<expr> const & type, tag g) {
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expr m = C->m_ctx.mk_meta(type, g);
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environment const & env = C->env();
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justification j = mk_failed_to_synthesize_jst(env, m);
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auto choice_fn = [=](expr const & meta, expr const & meta_type, substitution const & s,
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name_generator const & /* ngen */) {
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expr const & mvar = get_app_fn(meta);
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if (auto cls_name_it = is_ext_class(C->tc(), meta_type)) {
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name cls_name = *cls_name_it;
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list<expr> const & ctx = C->m_ctx.get_data();
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list<expr> local_insts;
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if (C->use_local_instances())
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local_insts = get_local_instances(C->tc(), ctx, cls_name);
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list<name> insts = get_class_instances(env, cls_name);
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list<tactic_hint_entry> tacs;
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if (!s.is_assigned(mvar))
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tacs = get_tactic_hints(env, cls_name);
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if (empty(local_insts) && empty(insts) && empty(tacs))
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return lazy_list<constraints>(); // nothing to be done
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// we are always strict with placeholders associated with classes
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bool ignore_failure = false;
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return choose(std::make_shared<placeholder_elaborator>(C, meta, meta_type, local_insts, insts, tacs,
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j, ignore_failure));
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} else if (s.is_assigned(mvar)) {
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// if the metavariable is assigned and it is not a class, then we just ignore it, and return
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// the an empty set of constraints.
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return lazy_list<constraints>(constraints());
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} else {
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list<tactic_hint_entry> tacs = get_tactic_hints(env);
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bool ignore_failure = !is_strict;
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return choose(std::make_shared<placeholder_elaborator>(C, meta, meta_type, list<expr>(), list<name>(),
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tacs, j, ignore_failure));
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}
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};
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bool owner = false;
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bool relax = C->m_relax;
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constraint c = mk_choice_cnstr(m, choice_fn, to_delay_factor(cnstr_group::ClassInstance),
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owner, j, relax);
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return mk_pair(m, c);
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}
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/** \brief Create a metavariable, and attach choice constraint for generating
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solutions using class-instances and tactic-hints.
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*/
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pair<expr, constraint> mk_placeholder_elaborator(
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environment const & env, io_state const & ios, list<expr> const & ctx,
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name const & prefix, bool relax, bool use_local_instances,
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bool is_strict, optional<expr> const & type, tag g) {
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auto C = std::make_shared<placeholder_context>(env, ios, ctx, prefix, relax, use_local_instances);
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return mk_placeholder_elaborator(C, is_strict, type, g);
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}
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}
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