340 lines
15 KiB
C++
340 lines
15 KiB
C++
/*
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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 "util/lazy_list_fn.h"
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#include "util/flet.h"
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#include "util/sexpr/option_declarations.h"
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#include "kernel/instantiate.h"
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#include "kernel/for_each_fn.h"
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#include "kernel/abstract.h"
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#include "kernel/error_msgs.h"
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#include "library/unifier.h"
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#include "library/reducible.h"
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#include "library/metavar_closure.h"
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#include "library/error_handling/error_handling.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/local_context.h"
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#include "frontends/lean/choice_iterator.h"
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#include "frontends/lean/elaborator_exception.h"
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#ifndef LEAN_DEFAULT_ELABORATOR_UNIQUE_CLASS_INSTANCES
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#define LEAN_DEFAULT_ELABORATOR_UNIQUE_CLASS_INSTANCES false
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#endif
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namespace lean {
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static name * g_elaborator_unique_class_instances = nullptr;
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void initialize_placeholder_elaborator() {
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g_elaborator_unique_class_instances = new name{"elaborator", "unique_class_instances"};
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register_bool_option(*g_elaborator_unique_class_instances, LEAN_DEFAULT_ELABORATOR_UNIQUE_CLASS_INSTANCES,
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"(elaborator) generate an error if there is more than one solution "
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"for a class-instance resolution problem");
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}
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void finalize_placeholder_elaborator() {
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delete g_elaborator_unique_class_instances;
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}
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bool get_elaborator_unique_class_instances(options const & o) {
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return o.get_bool(*g_elaborator_unique_class_instances, LEAN_DEFAULT_ELABORATOR_UNIQUE_CLASS_INSTANCES);
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}
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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, local_context 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(env, m_ngen.mk_child(), relax)),
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m_ctx(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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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) all global instances of class C
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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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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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justification const & j):
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choice_iterator(), m_C(C), m_meta(meta), m_meta_type(meta_type),
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m_local_instances(local_insts), m_instances(instances), m_jst(j) {
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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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flet<local_context> scope(ctx, 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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pair<expr, constraint> ac = mk_placeholder_elaborator(m_C, 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, 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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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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return optional<constraints>();
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}
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};
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constraint mk_placeholder_cnstr(std::shared_ptr<placeholder_context> const & C, expr const & m) {
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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 &, name_generator const &) {
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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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if (empty(local_insts) && empty(insts))
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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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return choose(std::make_shared<placeholder_elaborator>(C, meta, meta_type, local_insts, insts, j));
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} else {
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// do nothing, type is not a class...
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return lazy_list<constraints>(constraints());
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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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return mk_choice_cnstr(m, choice_fn, to_delay_factor(cnstr_group::ClassInstance),
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owner, j, relax);
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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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optional<expr> const & type, tag g) {
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expr m = C->m_ctx.mk_meta(C->m_ngen, type, g);
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constraint c = mk_placeholder_cnstr(C, m);
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return mk_pair(m, c);
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}
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/** \brief Similar to has_expr_metavar, but ignores metavariables occurring in the type
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of local constants */
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static bool has_expr_metavar_relaxed(expr const & e) {
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if (!has_expr_metavar(e))
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return false;
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bool found = false;
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for_each(e, [&](expr const & e, unsigned) {
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if (found || !has_expr_metavar(e))
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return false;
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if (is_metavar(e)) {
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found = true;
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return false;
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}
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if (is_local(e))
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return false; // do not visit type
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return true;
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});
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return found;
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}
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constraint mk_placeholder_root_cnstr(std::shared_ptr<placeholder_context> const & C, expr const & m, bool is_strict,
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unifier_config const & cfg, delay_factor const & factor) {
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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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if (!is_ext_class(C->tc(), meta_type)) {
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// do nothing, since type is not a class.
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return lazy_list<constraints>(constraints());
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}
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pair<expr, justification> mj = update_meta(meta, s);
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expr new_meta = mj.first;
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justification new_j = mj.second;
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constraint c = mk_placeholder_cnstr(C, new_meta);
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unifier_config new_cfg(cfg);
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new_cfg.m_discard = false;
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new_cfg.m_use_exceptions = false;
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auto to_cnstrs_fn = [=](substitution const & subst, constraints const & cnstrs) {
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substitution new_s = subst;
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// some constraints may have been postponed (example: universe level constraints)
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constraints postponed = map(cnstrs,
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[&](constraint const & c) {
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// we erase internal justifications
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return update_justification(c, mk_composite1(j, new_j));
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});
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metavar_closure cls(new_meta);
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cls.add(meta_type);
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bool relax = C->m_relax;
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constraints cs = cls.mk_constraints(new_s, new_j, relax);
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return append(cs, postponed);
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};
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unify_result_seq seq1 = unify(env, 1, &c, ngen, substitution(), new_cfg);
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if (get_elaborator_unique_class_instances(C->m_ios.get_options())) {
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optional<expr> solution;
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substitution subst;
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constraints cnstrs;
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for_each(seq1, [&](pair<substitution, constraints> const & p) {
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subst = p.first;
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cnstrs = p.second;
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expr next_solution = subst.instantiate(new_meta);
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if (solution) {
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throw_elaborator_exception(env, m, [=](formatter const & fmt) {
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format r = format("ambiguous class-instance resolution, "
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"there is more than one solution");
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r += pp_indent_expr(fmt, *solution);
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r += compose(line(), format("and"));
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r += pp_indent_expr(fmt, next_solution);
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return r;
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});
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} else {
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solution = next_solution;
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}
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});
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if (!solution) {
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if (is_strict)
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return lazy_list<constraints>();
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else
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return lazy_list<constraints>(constraints());
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} else {
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// some constraints may have been postponed (example: universe level constraints)
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return lazy_list<constraints>(to_cnstrs_fn(subst, cnstrs));
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}
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} else {
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unify_result_seq seq2 = filter(seq1, [=](pair<substitution, constraints> const & p) {
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substitution new_s = p.first;
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expr result = new_s.instantiate(new_meta);
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// We only keep complete solutions (modulo universe metavariables)
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return !has_expr_metavar_relaxed(result);
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});
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lazy_list<constraints> seq3 = map2<constraints>(seq2, [=](pair<substitution, constraints> const & p) {
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return to_cnstrs_fn(p.first, p.second);
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});
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if (is_strict) {
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return seq3;
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} else {
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// make sure it does not fail by appending empty set of constraints
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return append(seq3, lazy_list<constraints>(constraints()));
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}
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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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return mk_choice_cnstr(m, choice_fn, factor, owner, j, relax);
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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
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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, local_context const & ctx,
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name const & prefix, optional<name> const & suffix, bool relax, bool use_local_instances,
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bool is_strict, optional<expr> const & type, tag g, unifier_config const & cfg) {
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auto C = std::make_shared<placeholder_context>(env, ios, ctx, prefix, relax, use_local_instances);
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expr m = C->m_ctx.mk_meta(C->m_ngen, suffix, type, g);
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constraint c = mk_placeholder_root_cnstr(C, m, is_strict, cfg, delay_factor());
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return mk_pair(m, c);
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}
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}
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