blog-static/code/compiler/03/ast.cpp

#include "ast.hpp"

std::string op_name(binop op) {
    switch(op) {
        case PLUS: return "+";
        case MINUS: return "-";
        case TIMES: return "*";
        case DIVIDE: return "/";
    }
    throw 0;
}

type_ptr ast_int::typecheck(type_mgr& mgr, const type_env& env) const {
    return type_ptr(new type_base("Int"));
}

type_ptr ast_lid::typecheck(type_mgr& mgr, const type_env& env) const {
    return env.lookup(id);
}

type_ptr ast_uid::typecheck(type_mgr& mgr, const type_env& env) const {
    return env.lookup(id);
}

type_ptr ast_binop::typecheck(type_mgr& mgr, const type_env& env) const {
    type_ptr ltype = left->typecheck(mgr, env);
    type_ptr rtype = right->typecheck(mgr, env);
    type_ptr ftype = env.lookup(op_name(op));
    if(!ftype) throw 0;

    type_ptr place_a = mgr.new_type();
    type_ptr place_b = mgr.new_type();
    type_ptr place_c = mgr.new_type();
    type_ptr arrow_one = type_ptr(new type_arr(place_b, place_c));
    type_ptr arrow_two = type_ptr(new type_arr(place_a, arrow_one));

    mgr.unify(arrow_two, ftype);
    mgr.unify(place_a, ltype);
    mgr.unify(place_b, rtype);
    return place_c;
}

type_ptr ast_app::typecheck(type_mgr& mgr, const type_env& env) const {
    type_ptr ltype = left->typecheck(mgr, env);
    type_ptr rtype = right->typecheck(mgr, env);

    type_ptr place_a = mgr.new_type();
    type_ptr place_b = mgr.new_type();
    type_ptr arrow = type_ptr(new type_arr(place_a, place_b));
    mgr.unify(arrow, ltype);
    mgr.unify(place_a, rtype);
    return place_b;
}

type_ptr ast_case::typecheck(type_mgr& mgr, const type_env& env) const {
    type_ptr case_type = of->typecheck(mgr, env);
    type_ptr branch_type = mgr.new_type();

    for(auto& branch : branches) {
        type_env new_env = env.scope();
        branch->pat->match(case_type, mgr, new_env);
        type_ptr curr_branch_type = branch->expr->typecheck(mgr, new_env);
        mgr.unify(branch_type, curr_branch_type);
    }

    return branch_type;
}

void pattern_var::match(type_ptr t, type_mgr& mgr, type_env& env) const {
    env.bind(var, t);
}

void pattern_constr::match(type_ptr t, type_mgr& mgr, type_env& env) const {
    type_ptr constructor_type = env.lookup(constr);
    if(!constructor_type) throw 0;

    for(int i = 0; i < params.size(); i++) {
        type_arr* arr = dynamic_cast<type_arr*>(constructor_type.get());
        if(!arr) throw 0;

        env.bind(params[i], arr->left);
        constructor_type = arr->right;
    }

    mgr.unify(t, constructor_type);
    type_base* result_type = dynamic_cast<type_base*>(constructor_type.get());
    if(!result_type) throw 0;
}