/*
Copyright (c) 2016 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.

Author: Leonardo de Moura
*/
#include "util/timeit.h"
#include "kernel/type_checker.h"
#include "kernel/declaration.h"
#include "kernel/instantiate.h"
#include "kernel/replace_fn.h"
#include "library/trace.h"
#include "library/constants.h"
#include "library/explicit.h"
#include "library/typed_expr.h"
#include "library/private.h"
#include "library/protected.h"
#include "library/scoped_ext.h"
#include "library/unfold_macros.h"
#include "library/noncomputable.h"
#include "library/module.h"
#include "library/scope_pos_info_provider.h"
#include "library/replace_visitor.h"
#include "library/equations_compiler/equations.h"
#include "library/compiler/vm_compiler.h"
#include "library/compiler/rec_fn_macro.h"
#include "library/tactic/eqn_lemmas.h"
#include "frontends/lean/parser.h"
#include "frontends/lean/tokens.h"
#include "frontends/lean/elaborator.h"
#include "frontends/lean/util.h"
#include "frontends/lean/decl_util.h"
#include "frontends/lean/decl_attributes.h"
#include "frontends/lean/definition_cmds.h"
#include "frontends/lean/update_environment_exception.h"

// We don't display profiling information for declarations that take less than 0.01 secs
#ifndef LEAN_PROFILE_THRESHOLD
#define LEAN_PROFILE_THRESHOLD 0.01
#endif

namespace lean {
environment ensure_decl_namespaces(environment const & env, name const & full_n) {
    if (full_n.is_atomic())
        return env;
    return add_namespace(env, full_n.get_prefix());
}

expr parse_equation_lhs(parser & p, expr const & fn, buffer<expr> & locals) {
    auto lhs_pos = p.pos();
    buffer<expr> lhs_args;
    lhs_args.push_back(p.parse_pattern_or_expr(get_max_prec()));
    while (!p.curr_is_token(get_assign_tk())) {
        lhs_args.push_back(p.parse_pattern_or_expr(get_max_prec()));
    }
    expr lhs = p.mk_app(p.save_pos(mk_explicit(fn), lhs_pos), lhs_args, lhs_pos);
    bool skip_main_fn = true;
    return p.patexpr_to_pattern(lhs, skip_main_fn, locals);
}

expr parse_equation(parser & p, expr const & fn) {
    p.check_token_next(get_bar_tk(), "invalid equation, '|' expected");
    buffer<expr> locals;
    expr lhs = parse_equation_lhs(p, fn, locals);
    auto assign_pos = p.pos();
    p.check_token_next(get_assign_tk(), "invalid equation, ':=' expected");
    expr rhs = p.parse_scoped_expr(locals);
    return Fun(locals, p.save_pos(mk_equation(lhs, rhs), assign_pos), p);
}

optional<expr_pair> parse_using_well_founded(parser & p) {
    if (p.curr_is_token(get_using_well_founded_tk())) {
        p.next();
        expr R   = p.parse_expr(get_max_prec());
        expr Rwf = p.parse_expr(get_max_prec());
        return optional<expr_pair>(R, Rwf);
    } else {
        return optional<expr_pair>();
    }
}

expr mk_equations(parser & p, buffer<expr> const & fns, buffer<name> const & fn_full_names, buffer<expr> const & eqs,
                  optional<expr_pair> const & R_Rwf, pos_info const & pos) {
    buffer<expr> new_eqs;
    for (expr const & eq : eqs) {
        new_eqs.push_back(Fun(fns, eq, p));
    }
    equations_header h = mk_equations_header(to_list(fn_full_names));
    if (R_Rwf) {
        return p.save_pos(mk_equations(h, new_eqs.size(), new_eqs.data(), R_Rwf->first, R_Rwf->second), pos);
    } else {
        return p.save_pos(mk_equations(h, new_eqs.size(), new_eqs.data()), pos);
    }
}

expr mk_equations(parser & p, expr const & fn, name const & full_name, buffer<expr> const & eqs,
                  optional<expr_pair> const & R_Rwf, pos_info const & pos) {
    buffer<expr> fns; fns.push_back(fn);
    buffer<name> full_names; full_names.push_back(full_name);
    return mk_equations(p, fns, full_names, eqs, R_Rwf, pos);
}

expr parse_mutual_definition(parser & p, buffer<name> & lp_names, buffer<expr> & fns, buffer<expr> & params) {
    parser::local_scope scope1(p);
    auto header_pos = p.pos();
    buffer<expr> pre_fns;
    parse_mutual_header(p, lp_names, pre_fns, params);
    buffer<expr> eqns;
    buffer<name> full_names;
    for (expr const & pre_fn : pre_fns) {
        // TODO(leo, dhs): make use of attributes
        expr fn_type = parse_inner_header(p, local_pp_name(pre_fn)).first;
        declaration_name_scope scope2(local_pp_name(pre_fn));
        declaration_name_scope scope3("_main");
        full_names.push_back(scope2.get_name());
        if (p.curr_is_token(get_period_tk())) {
            auto period_pos = p.pos();
            p.next();
            eqns.push_back(p.save_pos(mk_no_equation(), period_pos));
        } else {
            while (p.curr_is_token(get_bar_tk())) {
                eqns.push_back(parse_equation(p, pre_fn));
            }
            if (!p.curr_is_command() && !p.curr_is_eof()) {
                throw parser_error("invalid equations, must be followed by a command or EOF", p.pos());
            }
        }
        expr fn      = mk_local(mlocal_name(pre_fn), local_pp_name(pre_fn), fn_type, mk_rec_info(true));
        fns.push_back(fn);
    }
    if (p.curr_is_token(get_with_tk()))
        throw parser_error("unexpected 'with' clause", p.pos());
    optional<expr_pair> R_Rwf = parse_using_well_founded(p);
    for (expr & eq : eqns) {
        eq = replace_locals_preserving_pos_info(eq, pre_fns, fns);
    }
    expr r = mk_equations(p, fns, full_names, eqns, R_Rwf, header_pos);
    collect_implicit_locals(p, lp_names, params, r);
    return r;
}

environment mutual_definition_cmd_core(parser & p, def_cmd_kind kind, decl_modifiers const & modifiers, decl_attributes /* attrs */) {
    buffer<name> lp_names;
    buffer<expr> fns, params;
    declaration_info_scope scope(p, kind, modifiers);
    expr val = parse_mutual_definition(p, lp_names, fns, params);
    elaborator elab(p.env(), p.get_options(), metavar_context(), local_context());
    buffer<expr> new_params;
    elaborate_params(elab, params, new_params);
    val = replace_locals_preserving_pos_info(val, params, new_params);

    // TODO(Leo)
    for (auto p : new_params) { tout() << ">> " << p << " : " << mlocal_type(p) << "\n"; }
    tout() << val << "\n";

    return p.env();
}

static expr_pair parse_definition(parser & p, buffer<name> & lp_names, buffer<expr> & params,
                                  bool is_example, bool is_instance) {
    parser::local_scope scope1(p);
    auto header_pos = p.pos();
    expr fn = parse_single_header(p, lp_names, params, is_example, is_instance);
    declaration_name_scope scope2(local_pp_name(fn));
    expr val;
    if (p.curr_is_token(get_assign_tk())) {
        p.next();
        val = p.parse_expr();
    } else if (p.curr_is_token(get_bar_tk()) || p.curr_is_token(get_period_tk())) {
        declaration_name_scope scope2("_main");
        fn = mk_local(mlocal_name(fn), local_pp_name(fn), mlocal_type(fn), mk_rec_info(true));
        p.add_local(fn);
        buffer<expr> eqns;
        if (p.curr_is_token(get_period_tk())) {
            auto period_pos = p.pos();
            p.next();
            eqns.push_back(p.save_pos(mk_no_equation(), period_pos));
        } else {
            while (p.curr_is_token(get_bar_tk())) {
                eqns.push_back(parse_equation(p, fn));
            }
            if (!p.curr_is_command() && !p.curr_is_eof()) {
                throw parser_error("invalid equations, must be followed by a command or EOF", p.pos());
            }
        }
        optional<expr_pair> R_Rwf = parse_using_well_founded(p);
        val = mk_equations(p, fn, scope2.get_name(), eqns, R_Rwf, header_pos);
    } else {
        throw parser_error("invalid definition, '|' or ':=' expected", p.pos());
    }
    collect_implicit_locals(p, lp_names, params, {mlocal_type(fn), val});
    return mk_pair(fn, val);
}

static void replace_params(buffer<expr> const & params, buffer<expr> const & new_params, expr & fn, expr & val) {
    expr fn_type = replace_locals_preserving_pos_info(mlocal_type(fn), params, new_params);
    expr new_fn  = update_mlocal(fn, fn_type);
    val          = replace_locals_preserving_pos_info(val, params, new_params);
    val          = replace_local_preserving_pos_info(val, fn, new_fn);
    fn           = new_fn;
}

static expr_pair elaborate_theorem(elaborator & elab, expr const & fn, expr val) {
    expr fn_type = elab.elaborate_type(mlocal_type(fn));
    elab.ensure_no_unassigned_metavars(fn_type);
    expr new_fn  = update_mlocal(fn, fn_type);
    val = replace_local_preserving_pos_info(val, fn, new_fn);
    return elab.elaborate_with_type(val, mk_as_is(fn_type));
}

static expr_pair elaborate_definition_core(elaborator & elab, def_cmd_kind kind, expr const & fn, expr const & val) {
    if (kind == Theorem) {
        return elaborate_theorem(elab, fn, val);
    } else {
        return elab.elaborate_with_type(val, mlocal_type(fn));
    }
}

static expr_pair elaborate_definition(parser & p, elaborator & elab, def_cmd_kind kind, expr const & fn, expr const & val, pos_info const & pos) {
    if (p.profiling()) {
        auto msg = p.mk_message(pos, INFORMATION);
        msg << "elaboration time for " << fn;
        expr_pair result;
        {
            timeit timer(msg.get_text_stream().get_stream(), "", LEAN_PROFILE_THRESHOLD);
            result = elaborate_definition_core(elab, kind, fn, val);
        }
        msg.report();
        return result;
    } else {
        return elaborate_definition_core(elab, kind, fn, val);
    }
}

static void finalize_definition(elaborator & elab, buffer<expr> const & params, expr & type, expr & val, buffer<name> & lp_names) {
    type = elab.mk_pi(params, type);
    val  = elab.mk_lambda(params, val);
    buffer<expr> type_val;
    buffer<name> implicit_lp_names;
    type_val.push_back(type);
    type_val.push_back(val);
    elab.finalize(type_val, implicit_lp_names, true, false);
    type = unfold_untrusted_macros(elab.env(), type_val[0]);
    val  = unfold_untrusted_macros(elab.env(), type_val[1]);
    lp_names.append(implicit_lp_names);
}

static pair<environment, name> mk_real_name(environment const & env, name const & c_name, bool is_private, pos_info const & pos) {
    environment new_env = env;
    name c_real_name;
    if (is_private) {
        unsigned h  = hash(pos.first, pos.second);
        auto env_n  = add_private_name(new_env, c_name, optional<unsigned>(h));
        new_env     = env_n.first;
        c_real_name = env_n.second;
    } else {
        name const & ns = get_namespace(env);
        c_real_name     = ns + c_name;
    }
    return mk_pair(new_env, c_real_name);
}

static certified_declaration check(parser & p, environment const & env, name const & c_name, declaration const & d, pos_info const & pos) {
    if (p.profiling()) {
        auto msg = p.mk_message(pos, INFORMATION);
        msg << "type checking time for " << c_name;
        std::shared_ptr<timeit> timer = std::make_shared<timeit>(
                msg.get_text_stream().get_stream(), "", LEAN_PROFILE_THRESHOLD);
        auto result = ::lean::check(env, d);
        timer.reset();
        msg.report();
        return result;
    } else {
        return ::lean::check(env, d);
    }
}

static void check_noncomputable(parser & p, environment const & env, name const & c_name, name const & c_real_name, bool is_noncomputable) {
    if (p.ignore_noncomputable())
        return;
    if (!is_noncomputable && is_marked_noncomputable(env, c_real_name)) {
        auto reason = get_noncomputable_reason(env, c_real_name);
        lean_assert(reason);
        throw exception(sstream() << "definition '" << c_name << "' is noncomputable, it depends on '" << *reason << "'");
    }
    if (is_noncomputable && !is_marked_noncomputable(env, c_real_name)) {
        throw exception(sstream() << "definition '" << c_name << "' was incorrectly marked as noncomputable");
    }
}

static environment compile_decl(parser & p, environment const & env, def_cmd_kind kind, bool is_noncomputable,
                                name const & c_name, name const & c_real_name, pos_info const & pos) {
    if (is_noncomputable || kind == Theorem || kind == Example || is_vm_builtin_function(c_real_name))
        return env;
    try {
        declaration d = env.get(c_real_name);
        return vm_compile(env, d);
    } catch (exception & ex) {
        if (p.found_errors())
            return env;
        // FIXME(gabriel): use position from exception
        auto out = p.mk_message(pos, WARNING);
        out << "failed to generate bytecode for '" << c_name << "'\n";
        out.set_exception(ex);
        out.report();
        return env;
    }
}

static expr fix_rec_fn_name(expr const & e, name const & c_name, name const & c_real_name) {
    return replace(e, [&](expr const & m, unsigned) {
            if (is_rec_fn_macro(m) && get_rec_fn_name(m) == c_name) {
                return some_expr(mk_rec_fn_macro(c_real_name, get_rec_fn_type(m)));
            }
            return none_expr();
        });
}

static pair<environment, name>
declare_definition(parser & p, environment const & env, def_cmd_kind kind, buffer<name> const & lp_names,
                   name const & c_name, expr const & type, expr const & _val,
                   decl_modifiers const & modifiers, decl_attributes attrs, pos_info const & pos) {
    auto env_n = mk_real_name(env, c_name, modifiers.m_is_private, pos);
    environment new_env = env_n.first;
    name c_real_name    = env_n.second;
    expr val            = _val;
    if (modifiers.m_is_meta)
        val = fix_rec_fn_name(val, c_name, c_real_name);
    bool use_conv_opt = true;
    bool is_trusted   = !modifiers.m_is_meta;
    auto def          = kind == Theorem ?
        mk_theorem(c_real_name, to_list(lp_names), type, val) :
        mk_definition(new_env, c_real_name, to_list(lp_names), type, val, use_conv_opt, is_trusted);
    auto cdef         = check(p, new_env, c_name, def, pos);
    new_env           = module::add(new_env, cdef);

    check_noncomputable(p, new_env, c_name, c_real_name, modifiers.m_is_noncomputable);

    if (kind == Example)
        return mk_pair(env, c_real_name);

    if (modifiers.m_is_protected)
        new_env = add_protected(new_env, c_real_name);

    new_env = add_alias(new_env, modifiers.m_is_protected, c_name, c_real_name);

    if (!modifiers.m_is_private) {
        new_env = ensure_decl_namespaces(new_env, c_real_name);
    }

    new_env = attrs.apply(new_env, p.ios(), c_real_name);
    new_env = compile_decl(p, new_env, kind, modifiers.m_is_noncomputable, c_name, c_real_name, pos);
    return mk_pair(new_env, c_real_name);
}

struct fix_rec_fn_macro_args_fn : public replace_visitor {
    buffer<expr> const &             m_params;
    buffer<pair<name, expr>> const & m_fns;

    fix_rec_fn_macro_args_fn(buffer<expr> const & params, buffer<pair<name, expr>> const & fns):
        m_params(params), m_fns(fns) {
    }

    expr fix_rec_fn_macro(name const & fn, expr const & type) {
        return mk_app(mk_rec_fn_macro(fn, type), m_params);
    }

    virtual expr visit_macro(expr const & e) override {
        if (is_rec_fn_macro(e)) {
            name n = get_rec_fn_name(e);
            for (unsigned i = 0; i < m_fns.size(); i++) {
                if (n == m_fns[i].first)
                    return fix_rec_fn_macro(m_fns[i].first, m_fns[i].second);
            }
        }
        return replace_visitor::visit_macro(e);
    }
};

static expr fix_rec_fn_macro_args(elaborator & elab, name const & fn, buffer<expr> const & params, expr const & type, expr const & val) {
    expr fn_new_type = elab.mk_pi(params, type);
    buffer<pair<name, expr>> fns;
    fns.emplace_back(fn, fn_new_type);
    return fix_rec_fn_macro_args_fn(params, fns)(val);
}

static void throw_unexpected_error_at_copy_lemmas() {
    throw exception("unexpected error, failed to generate equational lemmas in the front-end");
}

/* Given e of the form Pi (a_1 : A_1) ... (a_n : A_n), lhs = rhs,
   return the pair (lhs, n) */
static pair<expr, unsigned> get_lemma_lhs(expr e) {
    unsigned nparams = 0;
    while (is_pi(e)) {
        nparams++;
        e = binding_body(e);
    }
    expr lhs, rhs;
    if (!is_eq(e, lhs, rhs))
        throw_unexpected_error_at_copy_lemmas();
    return mk_pair(lhs, nparams);
}

/*
   Given a lemma with parameters lp_names:
      [lp_1 ... lp_n]
   and the levels in the function application on the lemma left-hand-side lhs_fn_levels:
      [u_1 ... u_n] s.t. there is a permutation p s.t. p([u_1 ... u_n] = [(mk_univ_param lp_1) ... (mk_univ_param lp_n)],
   and levels fn_levels
      [v_1 ... v_n]
   Then, store
      p([v_1 ... v_n])
   in result.
*/
static void get_levels_for_instantiating_lemma(level_param_names const & lp_names,
                                               levels const & lhs_fn_levels,
                                               levels const & fn_levels,
                                               buffer<level> & result) {
    buffer<level> fn_levels_buffer;
    buffer<level> lhs_fn_levels_buffer;
    to_buffer(fn_levels, fn_levels_buffer);
    to_buffer(lhs_fn_levels, lhs_fn_levels_buffer);
    lean_assert(fn_levels_buffer.size() == lhs_fn_levels_buffer.size());
    for (name const & lp_name : lp_names) {
        unsigned j = 0;
        for (; j < lhs_fn_levels_buffer.size(); j++) {
            if (!is_param(lhs_fn_levels_buffer[j])) throw_unexpected_error_at_copy_lemmas();
            if (param_id(lhs_fn_levels_buffer[j]) == lp_name) {
                result.push_back(fn_levels_buffer[j]);
                break;
            }
        }
        lean_assert(j < lhs_fn_levels_buffer.size());
    }
}

/**
   Given a lemma with the given arity (i.e., number of nested Pi-terms),
   n = args.size() <= lhs_args.size(), and the first n
   arguments in lhs_args.size() are a permutation p of
     (var #0) ... (var #n-1)
   Then, store in result p(args)
*/
static void get_args_for_instantiating_lemma(unsigned arity,
                                             buffer<expr> const & lhs_args,
                                             buffer<expr> const & args,
                                             buffer<expr> & result) {
    for (unsigned i = 0; i < args.size(); i++) {
        if (!is_var(lhs_args[i]) || var_idx(lhs_args[i]) >= arity)
            throw_unexpected_error_at_copy_lemmas();
        result.push_back(args[arity - var_idx(lhs_args[i]) - 1]);
    }
}

/* Return true iff e is of the form (fun (a_1 : A_1) ... (a_n : A_n), eq.refl ...) */
static bool is_refl_lemma(expr e) {
    while (is_lambda(e))
        e = binding_body(e);
    expr const & fn = get_app_fn(e);
    return is_constant(fn, get_eq_refl_name()) || is_constant(fn, get_rfl_name());
}

/**
   Given a declaration d defined as
     (fun (a_1 : A_1) ... (a_n : A_n), d._main a_1' ... a_n')
   where a_1' ... a_n' is a permutation of a_1 ... a_n.
   Then, copy the equation lemmas from d._main to d.
*/
static environment copy_equation_lemmas(environment const & env, name const & d_name) {
    declaration const & d = env.get(d_name);
    levels lps = param_names_to_levels(d.get_univ_params());
    expr val   = instantiate_value_univ_params(d, lps);
    type_context ctx(env, transparency_mode::All);
    type_context::tmp_locals locals(ctx);
    while (is_lambda(val)) {
        expr local = locals.push_local_from_binding(val);
        val = instantiate(binding_body(val), local);
    }
    buffer<expr> args;
    expr const & fn = get_app_args(val, args);
    if (!is_constant(fn) ||
        !std::all_of(args.begin(), args.end(), is_local) ||
        length(const_levels(fn)) != length(lps)) {
        throw_unexpected_error_at_copy_lemmas();
    }
    /* We want to create new equations where we replace val with new_val in the equations
       associated with fn. */
    expr new_val = mk_app(mk_constant(d_name, lps), locals.as_buffer());
    /* Copy equations */
    environment new_env = env;
    unsigned i = 1;
    while (true) {
        name eqn_suffix = name({"equations", "eqn"}).append_after(i);
        name eqn_name = const_name(fn) + eqn_suffix;
        optional<declaration> eqn_decl = env.find(eqn_name);
        if (!eqn_decl) break;
        unsigned num_eqn_levels = eqn_decl->get_num_univ_params();
        if (num_eqn_levels != length(lps))
            throw_unexpected_error_at_copy_lemmas();
        expr lhs; unsigned num_eqn_params;
        std::tie(lhs, num_eqn_params) = get_lemma_lhs(eqn_decl->get_type());
        buffer<expr> lhs_args;
        expr const & lhs_fn = get_app_args(lhs, lhs_args);
        if (!is_constant(lhs_fn) || const_name(lhs_fn) != const_name(fn) || lhs_args.size() < args.size())
            throw_unexpected_error_at_copy_lemmas();
        /* Get levels for instantiating the lemma */
        buffer<level> eqn_level_buffer;
        get_levels_for_instantiating_lemma(eqn_decl->get_univ_params(),
                                           const_levels(lhs_fn),
                                           const_levels(fn),
                                           eqn_level_buffer);
        levels eqn_levels = to_list(eqn_level_buffer);
        /* Get arguments for instantiating the lemma */
        buffer<expr> eqn_args;
        get_args_for_instantiating_lemma(num_eqn_params, lhs_args, args, eqn_args);
        /* Convert type */
        expr eqn_type = instantiate_type_univ_params(*eqn_decl, eqn_levels);
        for (unsigned j = 0; j < eqn_args.size(); j++) eqn_type = binding_body(eqn_type);
        eqn_type = instantiate_rev(eqn_type, eqn_args);
        expr new_eqn_type = replace(eqn_type, [&](expr const & e, unsigned) {
                if (e == val)
                    return some_expr(new_val);
                else
                    return none_expr();
            });
        new_eqn_type = locals.mk_pi(new_eqn_type);
        name new_eqn_name    = d_name + eqn_suffix;
        expr new_eqn_value;
        if (is_refl_lemma(eqn_decl->get_value())) {
            /* Create a refl-lemma to make sure it can be used by the defeq simplifier. */
            type_context::tmp_locals extra_locals(ctx);
            while (is_pi(eqn_type)) {
                expr local = extra_locals.push_local_from_binding(eqn_type);
                eqn_type = instantiate(binding_body(eqn_type), local);
            }
            expr lhs, rhs;
            lean_verify(is_eq(eqn_type, lhs, rhs));
            new_eqn_value = mk_eq_refl(ctx, lhs);
            new_eqn_value = extra_locals.mk_lambda(new_eqn_value);
        } else {
            new_eqn_value = mk_app(mk_constant(eqn_name, eqn_levels), args);
        }
        new_eqn_value = locals.mk_lambda(new_eqn_value);
        declaration new_decl = mk_theorem(new_eqn_name, d.get_univ_params(), new_eqn_type, new_eqn_value);
        new_env = module::add(new_env, check(new_env, new_decl));
        new_env = add_eqn_lemma(new_env, new_eqn_name);
        i++;
    }
    return new_env;
}

environment single_definition_cmd_core(parser & p, def_cmd_kind kind, decl_modifiers modifiers, decl_attributes attrs) {
    buffer<name> lp_names;
    buffer<expr> params;
    expr fn, val;
    auto header_pos = p.pos();
    module::scope_pos_info scope_pos(header_pos);
    declaration_info_scope scope(p, kind, modifiers);
    bool is_example  = (kind == def_cmd_kind::Example);
    bool is_instance = modifiers.m_is_instance;
    bool aux_lemmas  = scope.gen_aux_lemmas();
    if (is_instance)
        attrs.set_attribute(p.env(), "instance");
    std::tie(fn, val) = parse_definition(p, lp_names, params, is_example, is_instance);
    elaborator elab(p.env(), p.get_options(), metavar_context(), local_context());
    buffer<expr> new_params;
    elaborate_params(elab, params, new_params);
    elab.set_instance_fingerprint();
    replace_params(params, new_params, fn, val);

    auto process = [&](expr val) -> environment {
        expr type;
        std::tie(val, type) = elaborate_definition(p, elab, kind, fn, val, header_pos);
        if (modifiers.m_is_meta) {
            val = fix_rec_fn_macro_args(elab, mlocal_name(fn), new_params, type, val);
        }
        bool eqns = is_equations_result(val);
        if (eqns) {
            lean_assert(is_equations_result(val));
            lean_assert(get_equations_result_size(val) == 1);
            val = get_equations_result(val, 0);
        }
        finalize_definition(elab, new_params, type, val, lp_names);
        name c_name = mlocal_name(fn);
        auto env_n  = declare_definition(p, elab.env(), kind, lp_names, c_name, type, val, modifiers, attrs, header_pos);
        if (kind == Example) return p.env();
        environment new_env = env_n.first;
        name c_real_name    = env_n.second;
        new_env = add_local_ref(p, new_env, c_name, c_real_name, lp_names, params);
        if (eqns && aux_lemmas) {
            new_env = copy_equation_lemmas(new_env, c_real_name);
        }
        return new_env;
    };

    try {
        return process(val);
    } catch (throwable & ex1) {
        if (kind == Example) throw;
        /* Try again using 'sorry' */
        expr sorry = p.mk_sorry(header_pos);
        modifiers.m_is_noncomputable = true;
        environment new_env;
        try {
            new_env = process(sorry);
        } catch (throwable & ex2) {
            /* Throw original error */
            ex1.rethrow();
        }
        std::shared_ptr<throwable> ex_ptr(ex1.clone());
        throw update_environment_exception(new_env, ex_ptr);
    }
}

environment definition_cmd_core(parser & p, def_cmd_kind kind, decl_modifiers const & modifiers, decl_attributes attrs) {
    if (modifiers.m_is_mutual)
        return mutual_definition_cmd_core(p, kind, modifiers, attrs);
    else
        return single_definition_cmd_core(p, kind, modifiers, attrs);
}
}