src/frontends/lean/decl_util.cpp

/*
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 <algorithm>
#include "kernel/instantiate.h"
#include "kernel/abstract.h"
#include "kernel/for_each_fn.h"
#include "kernel/replace_fn.h"
#include "library/locals.h"
#include "library/class.h"
#include "library/trace.h"
#include "library/placeholder.h"
#include "library/protected.h"
#include "library/private.h"
#include "library/aliases.h"
#include "library/explicit.h"
#include "library/reducible.h"
#include "library/scoped_ext.h"
#include "library/tactic/elaborate.h"
#include "frontends/lean/util.h"
#include "frontends/lean/decl_util.h"
#include "frontends/lean/tokens.h"
#include "frontends/lean/decl_attributes.h"
#include "frontends/lean/parser.h"
#include "frontends/lean/elaborator.h"

namespace lean {
bool parse_univ_params(parser & p, buffer<name> & lp_names) {
    if (p.curr_is_token(get_lcurly_tk())) {
        p.next();
        while (!p.curr_is_token(get_rcurly_tk())) {
            auto pos0 = p.pos();
            name l = p.check_atomic_id_next("invalid declaration, identifier expected");
            lp_names.push_back(l);
            p.add_local_level(l, mk_univ_param(l));
            if (p.pos() == pos0) break;
        }
        p.next();
        return true;
    } else {
        return false;
    }
}

expr parse_single_header(parser & p, declaration_name_scope & scope, buffer <name> & lp_names, buffer <expr> & params,
                         bool is_example, bool is_instance) {
    auto c_pos  = p.pos();
    name c_name;
    if (is_example) {
        c_name = "_example";
        scope.set_name(c_name);
    } else {
        if (!is_instance)
            parse_univ_params(p, lp_names);
        if (!is_instance || p.curr_is_identifier()) {
            c_name = p.check_decl_id_next("invalid declaration, identifier expected");
            scope.set_name(c_name);
        }
    }
    p.parse_optional_binders(params, /* allow_default */ true, /* explicit delimiters */ true);
    for (expr const & param : params)
        p.add_local(param);
    expr type;
    if (p.curr_is_token(get_colon_tk())) {
        p.next();
        type = p.parse_expr();
    } else {
        type = p.save_pos(mk_expr_placeholder(), c_pos);
    }
    if (is_instance && c_name.is_anonymous()) {
        if (used_match_idx())
            throw parser_error("invalid instance, pattern matching cannot be used in the type of anonymous instance declarations", c_pos);
        /* Try to synthesize name */
        expr it = type;
        while (is_pi(it)) it = binding_body(it);
        expr const & C = get_app_fn(it);
        name ns = get_namespace(p.env());
        if (is_constant(C) && !ns.is_anonymous()) {
            c_name = const_name(C);
            scope.set_name(c_name);
        } else if (is_constant(C) && is_app(it) && is_constant(get_app_fn(app_arg(it)))) {
            c_name = const_name(get_app_fn(app_arg(it))) + const_name(C);
            scope.set_name(c_name);
        } else {
            p.maybe_throw_error({"failed to synthesize instance name, name should be provided explicitly", c_pos});
            c_name = mk_unused_name(p.env(), "_inst");
        }
    }
    lean_assert(!c_name.is_anonymous());
    return p.save_pos(mk_local(c_name, type), c_pos);
}

void parse_mutual_header(parser & p, buffer <name> & lp_names, buffer <expr> & cs, buffer <expr> & params) {
    parse_univ_params(p, lp_names);
    while (true) {
        auto c_pos  = p.pos();
        name c_name = p.check_decl_id_next("invalid mutual declaration, identifier expected");
        cs.push_back(p.save_pos(mk_local(c_name, mk_expr_placeholder()), c_pos));
        if (!p.curr_is_token(get_comma_tk()))
            break;
        p.next();
    }
    if (cs.size() < 2) {
        throw parser_error("invalid mutual declaration, must provide more than one identifier (separated by commas)", p.pos());
    }
    p.parse_optional_binders(params, /* allow_default */ true, /* explicit delimiters */ true);
    for (expr const & param : params)
        p.add_local(param);
    for (expr const & c : cs)
        p.add_local(c);
}

pair<expr, decl_attributes> parse_inner_header(parser & p, name const & c_expected) {
    decl_attributes attrs;
    p.check_token_next(get_with_tk(), "invalid mutual declaration, 'with' expected");
    attrs.parse(p);
    auto id_pos = p.pos();
    name n = p.check_decl_id_next("invalid mutual declaration, identifier expected");
    if (c_expected != n)
        throw parser_error(sstream() << "invalid mutual declaration, '" << c_expected << "' expected",
                           id_pos);
    /* Remark: if this is a private definition, the private prefix must have been set
       before invoking this procedure. */
    declaration_name_scope scope(n);
    p.check_token_next(get_colon_tk(), "invalid mutual declaration, ':' expected");
    return mk_pair(p.parse_expr(), attrs);
}

/** \brief Version of collect_locals(expr const & e, collected_locals & ls) that ignores local constants occurring in
    tactics. */
void collect_locals_ignoring_tactics(expr const & e, collected_locals & ls) {
    if (!has_local(e)) return;
    for_each(e, [&](expr const & e, unsigned) {
            if (!has_local(e)) return false;
            if (is_by(e))      return false; // do not visit children
            if (is_local(e))   ls.insert(e);
            return true;
        });
}

name_set collect_univ_params_ignoring_tactics(expr const & e, name_set const & ls) {
    if (!has_param_univ(e)) return ls;
    name_set r = ls;
    for_each(e, [&](expr const & e, unsigned) {
            if (!has_param_univ(e)) {
                return false;
            } else if (is_by(e)) {
                return false;
            } else if (is_sort(e)) {
                collect_univ_params_core(sort_level(e), r);
            } else if (is_constant(e)) {
                for (auto const & l : const_levels(e))
                    collect_univ_params_core(l, r);
            }
            return true;
        });
    return r;
}

/** \brief Collect annonymous instances in section/namespace declarations such as:

        variable [decidable_eq A]

    Instances are included only if all section variables/parameters they reference have already
    been included. For variables in out_param position, the logic is inverted: If the instance is
    included, we also include those arguments.
*/
void collect_annonymous_inst_implicit(parser const & p, collected_locals & locals) {
    buffer<pair<name, expr>> entries;
    to_buffer(p.get_local_entries(), entries);
    type_context_old ctx(p.env());
    unsigned i = entries.size();
    while (i > 0) {
        --i;
        auto const & entry = entries[i];
        if (is_local(entry.second) && !locals.contains(entry.second) && is_inst_implicit(local_info(entry.second)) &&
            // remark: remove the following condition condition, if we want to auto inclusion also for non anonymous ones.
            is_anonymous_inst_name(entry.first)) {
            expr type = local_type(entry.second);
            buffer<expr> C_args;
            expr C = get_app_args(type, C_args);
            if (!is_const(C))
                continue;
            expr it2 = ctx.infer(C);
            collected_locals new_locals;
            bool ok = true;
            for (expr & C_arg : C_args) {
                it2  = ctx.relaxed_whnf(it2);
                lean_assert(is_pi(it2));
                expr const & d = binding_domain(it2);
                if (is_local(C_arg) && is_class_out_param(d)) {
                    new_locals.insert(C_arg);
                } else {
                    for_each(C_arg, [&](expr const & e, unsigned) {
                        if (!ok) return false; // stop
                        if (is_local(e) && !(locals.contains(e) || new_locals.contains(e)))
                            ok = false;
                        return true;
                    });
                }
                it2 = instantiate(binding_body(it2), C_arg);
            }
            if (ok) {
                for (auto & l : new_locals.get_collected()) {
                    locals.insert(l);
                }
                locals.insert(entry.second);
            }
        }
    }
}

/** \brief Sort local names by order of occurrence, and copy the associated parameters to ps */
void sort_locals(buffer<expr> const & locals, parser const & p, buffer<expr> & ps) {
    buffer<expr> extra;
    name_set     explicit_param_names;
    for (expr const & p : ps) {
        explicit_param_names.insert(local_name(p));
    }
    for (expr const & l : locals) {
        // we only copy the locals that are in p's local context
        if (p.is_local_decl_user_name(l) && !explicit_param_names.contains(local_name(l)))
            extra.push_back(l);
    }
    std::sort(extra.begin(), extra.end(), [&](expr const & p1, expr const & p2) {
            bool is_var1 = p.is_local_variable(p1);
            bool is_var2 = p.is_local_variable(p2);
            if (!is_var1 && is_var2)
                return true;
            else if (is_var1 && !is_var2)
                return false;
            else
                return p.get_local_index(p1) < p.get_local_index(p2);
        });
    buffer<expr> new_ps;
    new_ps.append(extra);
    new_ps.append(ps);
    ps.clear();
    ps.append(new_ps);
}

/** TODO(Leo): mark as static */
void update_univ_parameters(parser & p, buffer<name> & lp_names, name_set const & found) {
    unsigned old_sz = lp_names.size();
    found.for_each([&](name const & n) {
            if (std::find(lp_names.begin(), lp_names.begin() + old_sz, n) == lp_names.begin() + old_sz)
                lp_names.push_back(n);
        });
    std::sort(lp_names.begin(), lp_names.end(), [&](name const & n1, name const & n2) {
            return p.get_local_level_index(n1) < p.get_local_level_index(n2);
        });
}

expr replace_locals_preserving_pos_info(expr const & e, unsigned sz, expr const * from, expr const * to) {
    bool use_cache = false;
    return replace_propagating_pos(e, [&](expr const & e, unsigned) {
            if (is_local(e)) {
                unsigned i = sz;
                while (i > 0) {
                    --i;
                    if (local_name(from[i]) == local_name(e)) {
                        return some_expr(copy_pos(e, copy(to[i])));
                    }
                }
            }
            return none_expr();
        }, use_cache);
}

expr replace_locals_preserving_pos_info(expr const & e, buffer<expr> const & from, buffer<expr> const & to) {
    lean_assert(from.size() == to.size());
    return replace_locals_preserving_pos_info(e, from.size(), from.data(), to.data());
}

expr replace_local_preserving_pos_info(expr const & e, expr const & from, expr const & to) {
    return replace_locals_preserving_pos_info(e, 1, &from, &to);
}

void collect_implicit_locals(parser & p, buffer<name> & lp_names, buffer<expr> & params, buffer<expr> const & all_exprs) {
    collected_locals locals;
    buffer<expr> include_vars;
    name_set lp_found;
    name_set given_params;
    /* Process variables included using the 'include' command */
    p.get_include_variables(include_vars);
    for (expr const & param : include_vars) {
        if (is_local(param)) {
            collect_locals_ignoring_tactics(local_type(param), locals);
            lp_found = collect_univ_params_ignoring_tactics(local_type(param), lp_found);
            locals.insert(param);
        }
    }
    /* Process explicit parameters */
    for (expr const & param : params) {
        collect_locals_ignoring_tactics(local_type(param), locals);
        lp_found = collect_univ_params_ignoring_tactics(local_type(param), lp_found);
        locals.insert(param);
        given_params.insert(local_name(param));
    }
    /* Process expressions used to define declaration. */
    for (expr const & e : all_exprs) {
        collect_locals_ignoring_tactics(e, locals);
        lp_found = collect_univ_params_ignoring_tactics(e, lp_found);
    }
    collect_annonymous_inst_implicit(p, locals);
    sort_locals(locals.get_collected(), p, params);
    update_univ_parameters(p, lp_names, lp_found);
    /* Add as_is annotation to section variables and parameters */
    buffer<expr> old_params;
    for (unsigned i = 0; i < params.size(); i++) {
        expr & param = params[i];
        old_params.push_back(param);
        expr type          = local_type(param);
        expr new_type      = replace_locals_preserving_pos_info(type, i, old_params.data(), params.data());
        if (!given_params.contains(local_name(param))) {
            new_type = copy_pos(type, mk_as_is(new_type));
        }
        param = copy_pos(param, update_local(param, new_type));
    }
}

void collect_implicit_locals(parser & p, buffer<name> & lp_names, buffer<expr> & params, std::initializer_list<expr> const & all_exprs) {
    buffer<expr> tmp; tmp.append(all_exprs.size(), all_exprs.begin());
    collect_implicit_locals(p, lp_names, params, tmp);
}

void collect_implicit_locals(parser & p, buffer<name> & lp_names, buffer<expr> & params, expr const & e) {
    buffer<expr> all_exprs; all_exprs.push_back(e);
    collect_implicit_locals(p, lp_names, params, all_exprs);
}

void elaborate_params(elaborator & elab, buffer<expr> const & params, buffer<expr> & new_params) {
    for (unsigned i = 0; i < params.size(); i++) {
        expr const & param = params[i];
        expr type          = replace_locals_preserving_pos_info(local_type(param), i, params.data(), new_params.data());
        expr new_type      = elab.elaborate_type(type);
        expr new_param     = elab.push_local(local_pp_name(param), new_type, local_info(param));
        new_params.push_back(new_param);
    }
}

environment add_local_ref(parser & p, environment const & env, name const & c_name, name const & c_real_name, buffer<name> const & lp_names, buffer<expr> const & var_params) {
    buffer<expr> params;
    buffer<name> lps;
    for (name const & u : lp_names) {
        if (!p.is_local_level(u)) {
            /* Stop, it is a definition parameter */
            break;
        } else if (p.is_local_level_variable(u)) {
            /* Stop, it is a parser universe variable (i.e., it has been declared using the `universe variable` command */
            break;
        } else {
            lps.push_back(u);
        }
    }
    for (expr const & e : var_params) {
        if (!p.is_local_decl(e)) {
            /* Stop, it is a definition parameter */
            break;
        } else if (p.is_local_variable(e)) {
            /* Stop, it is a parser variable (i.e., it has been declared using the `variable` command */
            break;
        } else {
            /* It is a parser parameter (i.e., it has been declared with the `parameter` command */
            params.push_back(e);
        }
    }
    if (lps.empty() && params.empty()) return env;
    /*
      Procedures such as `collect_implicit_locals` wrap parameter types with the `as_is` annotation.
      So, we remove these annotations before creating the local reference using `mk_local_ref`.
      Remark: the resulting object is wrapped with the macro `as_atomic`.

      Remark: The local constants created here and `collect_implicit_locals` are not structurally
      equal. That is, `l : ty` is not structurally equal to `l : as_is ty`, but they are definitionally
      equal, and moreover the collection method relies on the fact that they have the same internal
      id.
    */
    buffer<expr> new_params;
    for (unsigned i = 0; i < params.size(); i++) {
        expr & param = params[i];
        expr type          = local_type(param);
        if (is_as_is(type))
            type = get_as_is_arg(type);
        expr new_type      = replace_locals_preserving_pos_info(type, i, params.data(), new_params.data());
        new_params.push_back(copy_pos(param, update_local(param, new_type)));
    }
    expr ref = mk_local_ref(c_real_name, param_names_to_levels(names(lps)), new_params);
    return p.add_local_ref(env, c_name, ref);
}

environment add_alias(environment const & env, bool is_protected, name const & c_name, name const & c_real_name) {
    if (c_name != c_real_name) {
        if (is_protected)
            return add_expr_alias_rec(env, get_protected_shortest_name(c_real_name), c_real_name);
        else
            return add_expr_alias_rec(env, c_name, c_real_name);
    } else {
        return env;
    }
}

struct definition_info {
    name     m_prefix; // prefix for local names
    name     m_actual_prefix; // actual prefix used to create kernel declaration names. m_prefix and m_actual_prefix are different for scoped/private declarations.
    bool     m_is_private{true}; // pattern matching outside of definitions should generate private names
    /* m_is_meta_decl == true iff declaration uses `meta` keyword */
    bool     m_is_meta_decl{false};
    /* m_is_meta == true iff the current subexpression can use meta declarations and code.
       Remark: a regular (i.e., non meta) declaration provided by the user may contain a meta subexpression (e.g., tactic).
    */
    bool     m_is_meta{false};      // true iff current block
    bool     m_is_noncomputable{false};
    bool     m_is_lemma{false};
    bool     m_aux_lemmas{false};
    unsigned m_next_match_idx{1};
};

MK_THREAD_LOCAL_GET_DEF(definition_info, get_definition_info);

declaration_info_scope::declaration_info_scope(name const & ns, decl_cmd_kind kind, decl_modifiers const & modifiers) {
    definition_info & info = get_definition_info();
    lean_assert(info.m_prefix.is_anonymous());
    info.m_prefix           = name(); // prefix is used to create local name
    /* Remark: if info.m_actual_prefix is not `anonymous`, then it has already been set using private_name_scope */
    if (info.m_actual_prefix.is_anonymous()) {
        info.m_actual_prefix = ns;
    }
    info.m_is_private       = modifiers.m_is_private;
    info.m_is_meta_decl     = modifiers.m_is_meta;
    info.m_is_meta          = modifiers.m_is_meta;
    info.m_is_noncomputable = modifiers.m_is_noncomputable;
    info.m_is_lemma         = kind == decl_cmd_kind::Theorem;
    info.m_aux_lemmas       = kind != decl_cmd_kind::Theorem && !modifiers.m_is_meta;
    info.m_next_match_idx = 1;
}

declaration_info_scope::declaration_info_scope(parser const & p, decl_cmd_kind kind, decl_modifiers const & modifiers):
    declaration_info_scope(get_namespace(p.env()), kind, modifiers) {}

declaration_info_scope::~declaration_info_scope() {
    get_definition_info() = definition_info();
}

bool declaration_info_scope::gen_aux_lemmas() const {
    return get_definition_info().m_aux_lemmas;
}

equations_header mk_equations_header(names const & ns, names const & actual_ns) {
    equations_header h;
    h.m_num_fns          = length(ns);
    h.m_fn_names         = ns;
    h.m_fn_actual_names  = actual_ns;
    h.m_is_private       = get_definition_info().m_is_private;
    h.m_is_meta          = get_definition_info().m_is_meta;
    h.m_is_noncomputable = get_definition_info().m_is_noncomputable;
    h.m_is_lemma         = get_definition_info().m_is_lemma;
    h.m_aux_lemmas       = get_definition_info().m_aux_lemmas;
    return h;
}

equations_header mk_equations_header(name const & n, name const & actual_n) {
    return mk_equations_header(names(n), names(actual_n));
}

equations_header mk_match_header(name const & n, name const & actual_n) {
    equations_header h = mk_equations_header(names(n), names(actual_n));
    h.m_gen_code = false;
    return h;
}

/* Auxiliary function for creating names for auxiliary declarations.
   We avoid propagating the suffix `_main` used by the top-level equations
   to the nested declarations. */
static name mk_decl_name(name const & prefix, name const & n) {
    if (!prefix.is_atomic() && prefix.is_string() && prefix.get_string() == "_main") {
        return prefix.get_prefix() + n;
    } else {
        return prefix + n;
    }
}

bool used_match_idx() {
    return get_definition_info().m_next_match_idx > 1;
}

declaration_name_scope::declaration_name_scope() {
    definition_info & info = get_definition_info();
    m_old_prefix          = info.m_prefix;
    m_old_actual_prefix   = info.m_actual_prefix;
    m_old_next_match_idx  = info.m_next_match_idx;
    info.m_next_match_idx = 1;
}

void declaration_name_scope::set_name(name const & n) {
    lean_assert(m_name.is_anonymous());
    definition_info & info    = get_definition_info();
    info.m_prefix             = mk_decl_name(info.m_prefix, n);
    info.m_actual_prefix      = mk_decl_name(info.m_actual_prefix, n);
    m_name                    = info.m_prefix;
    m_actual_name             = info.m_actual_prefix;
}

declaration_name_scope::declaration_name_scope(name const & n) {
    definition_info & info = get_definition_info();
    m_old_prefix          = info.m_prefix;
    m_old_actual_prefix   = info.m_actual_prefix;
    m_old_next_match_idx  = info.m_next_match_idx;
    info.m_prefix         = mk_decl_name(info.m_prefix, n);
    info.m_actual_prefix  = mk_decl_name(info.m_actual_prefix, n);
    info.m_next_match_idx = 1;
    m_name                = info.m_prefix;
    m_actual_name         = info.m_actual_prefix;
}

declaration_name_scope::~declaration_name_scope() {
    definition_info & info = get_definition_info();
    info.m_prefix          = m_old_prefix;
    info.m_actual_prefix  = m_old_actual_prefix;
    info.m_next_match_idx  = m_old_next_match_idx;
}

private_name_scope::private_name_scope(bool is_private, environment & env) {
    definition_info & info = get_definition_info();
    m_old_actual_prefix    = info.m_prefix;
    m_old_is_private       = info.m_is_private;
    if (is_private) {
        name prv_prefix;
        std::tie(env, prv_prefix) = mk_private_prefix(env);
        info.m_is_private     = true;
        info.m_actual_prefix = prv_prefix;
    }
}

private_name_scope::~private_name_scope() {
    definition_info & info = get_definition_info();
    info.m_actual_prefix   = m_old_actual_prefix;
    info.m_is_private      = m_old_is_private;
}

match_definition_scope::match_definition_scope(environment const & env) {
    definition_info & info = get_definition_info();
    while (true) {
        m_name        = mk_decl_name(info.m_prefix, name("_match").append_after(info.m_next_match_idx));
        m_actual_name = mk_decl_name(info.m_actual_prefix, name("_match").append_after(info.m_next_match_idx));
        info.m_next_match_idx++;
        if (empty(get_expr_aliases(env, m_name))) {
            /* Make sure we don't introduce aliases.
               This is important when match-expressions are used in several parameters in a section.
               Example:

                  parameter P : match ... end
                  parameter Q : match ... end
            */
            break;
        }
    }
}

meta_definition_scope::meta_definition_scope() {
    definition_info & info = get_definition_info();
    m_old_is_meta  = info.m_is_meta;
    info.m_is_meta = true;
}

meta_definition_scope::~meta_definition_scope() {
    definition_info & info = get_definition_info();
    info.m_is_meta = m_old_is_meta;
}

restore_decl_meta_scope::restore_decl_meta_scope() {
    definition_info & info = get_definition_info();
    m_old_is_meta  = info.m_is_meta;
    info.m_is_meta = info.m_is_meta_decl;
}

restore_decl_meta_scope::~restore_decl_meta_scope() {
    definition_info & info = get_definition_info();
    info.m_is_meta = m_old_is_meta;
}
}