Exemplo n.º 1
0
mp_lexer_t *mp_lexer_new(qstr src_name, mp_reader_t reader) {
    mp_lexer_t *lex = m_new_obj(mp_lexer_t);

    lex->source_name = src_name;
    lex->reader = reader;
    lex->line = 1;
    lex->column = (size_t)-2; // account for 3 dummy bytes
    lex->emit_dent = 0;
    lex->nested_bracket_level = 0;
    lex->alloc_indent_level = MICROPY_ALLOC_LEXER_INDENT_INIT;
    lex->num_indent_level = 1;
    lex->indent_level = m_new(uint16_t, lex->alloc_indent_level);
    vstr_init(&lex->vstr, 32);

    // store sentinel for first indentation level
    lex->indent_level[0] = 0;

    // load lexer with start of file, advancing lex->column to 1
    // start with dummy bytes and use next_char() for proper EOL/EOF handling
    lex->chr0 = lex->chr1 = lex->chr2 = 0;
    next_char(lex);
    next_char(lex);
    next_char(lex);

    // preload first token
    mp_lexer_to_next(lex);

    // Check that the first token is in the first column.  If it's not then we
    // convert the token kind to INDENT so that the parser gives a syntax error.
    if (lex->tok_column != 1) {
        lex->tok_kind = MP_TOKEN_INDENT;
    }

    return lex;
}
Exemplo n.º 2
0
STATIC void execute_from_lexer(mp_lexer_t *lex, mp_parse_input_kind_t input_kind, bool is_repl) {
    if (lex == NULL) {
        return;
    }

    if (0) {
        // just tokenise
        while (!mp_lexer_is_kind(lex, MP_TOKEN_END)) {
            mp_token_show(mp_lexer_cur(lex));
            mp_lexer_to_next(lex);
        }
        mp_lexer_free(lex);
        return;
    }

    mp_parse_error_kind_t parse_error_kind;
    mp_parse_node_t pn = mp_parse(lex, input_kind, &parse_error_kind);

    if (pn == MP_PARSE_NODE_NULL) {
        // parse error
        mp_parse_show_exception(lex, parse_error_kind);
        mp_lexer_free(lex);
        return;
    }

    qstr source_name = mp_lexer_source_name(lex);
    mp_lexer_free(lex);

    /*
    printf("----------------\n");
    mp_parse_node_print(pn, 0);
    printf("----------------\n");
    */

    mp_obj_t module_fun = mp_compile(pn, source_name, emit_opt, is_repl);

    if (module_fun == mp_const_none) {
        // compile error
        return;
    }

    if (compile_only) {
        return;
    }

    // execute it
    nlr_buf_t nlr;
    if (nlr_push(&nlr) == 0) {
        mp_call_function_0(module_fun);
        nlr_pop();
    } else {
        // uncaught exception
        mp_obj_print_exception((mp_obj_t)nlr.ret_val);
    }
}
Exemplo n.º 3
0
mp_lexer_t *mp_lexer_new(qstr src_name, mp_reader_t reader) {
    mp_lexer_t *lex = m_new_obj(mp_lexer_t);

    lex->source_name = src_name;
    lex->reader = reader;
    lex->line = 1;
    lex->column = 1;
    lex->emit_dent = 0;
    lex->nested_bracket_level = 0;
    lex->alloc_indent_level = MICROPY_ALLOC_LEXER_INDENT_INIT;
    lex->num_indent_level = 1;
    lex->indent_level = m_new(uint16_t, lex->alloc_indent_level);
    vstr_init(&lex->vstr, 32);

    // store sentinel for first indentation level
    lex->indent_level[0] = 0;

    // preload characters
    lex->chr0 = reader.readbyte(reader.data);
    lex->chr1 = reader.readbyte(reader.data);
    lex->chr2 = reader.readbyte(reader.data);

    // if input stream is 0, 1 or 2 characters long and doesn't end in a newline, then insert a newline at the end
    if (lex->chr0 == MP_LEXER_EOF) {
        lex->chr0 = '\n';
    } else if (lex->chr1 == MP_LEXER_EOF) {
        if (lex->chr0 == '\r') {
            lex->chr0 = '\n';
        } else if (lex->chr0 != '\n') {
            lex->chr1 = '\n';
        }
    } else if (lex->chr2 == MP_LEXER_EOF) {
        if (lex->chr1 == '\r') {
            lex->chr1 = '\n';
        } else if (lex->chr1 != '\n') {
            lex->chr2 = '\n';
        }
    }

    // preload first token
    mp_lexer_to_next(lex);

    // Check that the first token is in the first column.  If it's not then we
    // convert the token kind to INDENT so that the parser gives a syntax error.
    if (lex->tok_column != 1) {
        lex->tok_kind = MP_TOKEN_INDENT;
    }

    return lex;
}
Exemplo n.º 4
0
void do_file(const char *file) {
    mp_lexer_t *lex = mp_lexer_new_from_file(file);
    if (lex == NULL) {
        return;
    }

    if (0) {
        // just tokenise
        while (!mp_lexer_is_kind(lex, MP_TOKEN_END)) {
            mp_token_show(mp_lexer_cur(lex));
            mp_lexer_to_next(lex);
        }
        mp_lexer_free(lex);

    } else {
        // parse
        qstr parse_exc_id;
        const char *parse_exc_msg;
        mp_parse_node_t pn = mp_parse(lex, MP_PARSE_FILE_INPUT, &parse_exc_id, &parse_exc_msg);

        if (pn == MP_PARSE_NODE_NULL) {
            // parse error
            mp_lexer_show_error_pythonic_prefix(lex);
            printf("%s: %s\n", qstr_str(parse_exc_id), parse_exc_msg);
            mp_lexer_free(lex);
            return;
        }

        mp_lexer_free(lex);

        if (pn != MP_PARSE_NODE_NULL) {
            //printf("----------------\n");
            //mp_parse_node_print(pn, 0);
            //printf("----------------\n");

            // compile
            mp_obj_t module_fun = mp_compile(pn, 0, false);

            //printf("----------------\n");

            if (module_fun == mp_const_none) {
                printf("compile error\n");
            }
        }
    }
}
Exemplo n.º 5
0
void do_file(const char *file) {
    mp_lexer_t *lex = mp_lexer_new_from_file(file);
    if (lex == NULL) {
        return;
    }

    if (0) {
        // just tokenise
        while (lex->tok_kind != MP_TOKEN_END) {
            mp_lexer_show_token(lex);
            mp_lexer_to_next(lex);
        }
        mp_lexer_free(lex);

    } else {
        // parse
        mp_parse_error_kind_t parse_error_kind;
        mp_parse_node_t pn = mp_parse(lex, MP_PARSE_FILE_INPUT, &parse_error_kind);

        if (pn == MP_PARSE_NODE_NULL) {
            // parse error
            mp_parse_show_exception(lex, parse_error_kind);
            mp_lexer_free(lex);
            return;
        }

        mp_lexer_free(lex);

        if (pn != MP_PARSE_NODE_NULL) {
            //printf("----------------\n");
            //mp_parse_node_print(pn, 0);
            //printf("----------------\n");

            // compile
            mp_obj_t module_fun = mp_compile(pn, 0, MP_EMIT_OPT_NONE, false);

            //printf("----------------\n");

            if (mp_obj_is_exception_instance(module_fun)) {
                mp_obj_print_exception(module_fun);
            }
        }
    }
}
Exemplo n.º 6
0
void do_file(const char *file) {
    mp_lexer_t *lex = mp_lexer_new_from_file(file);
    if (lex == NULL) {
        return;
    }

    if (0) {
        // just tokenise
        while (!mp_lexer_is_kind(lex, MP_TOKEN_END)) {
            mp_token_show(mp_lexer_cur(lex));
            mp_lexer_to_next(lex);
        }
        mp_lexer_free(lex);

    } else {
        // parse
        mp_parse_error_kind_t parse_error_kind;
        mp_parse_node_t pn = mp_parse(lex, MP_PARSE_FILE_INPUT, &parse_error_kind);

        if (pn == MP_PARSE_NODE_NULL) {
            // parse error
            mp_parse_show_exception(lex, parse_error_kind);
            mp_lexer_free(lex);
            return;
        }

        mp_lexer_free(lex);

        if (pn != MP_PARSE_NODE_NULL) {
            //printf("----------------\n");
            //mp_parse_node_print(pn, 0);
            //printf("----------------\n");

            // compile
            mp_obj_t module_fun = mp_compile(pn, 0, false);

            //printf("----------------\n");

            if (module_fun == mp_const_none) {
                printf("compile error\n");
            }
        }
    }
}
Exemplo n.º 7
0
mp_parse_node_t mp_parse(mp_lexer_t *lex, mp_parse_input_kind_t input_kind) {

    // allocate memory for the parser and its stacks

    parser_t *parser = m_new_obj(parser_t);

    parser->rule_stack_alloc = 64;
    parser->rule_stack_top = 0;
    parser->rule_stack = m_new(rule_stack_t, parser->rule_stack_alloc);

    parser->result_stack_alloc = 64;
    parser->result_stack_top = 0;
    parser->result_stack = m_new(mp_parse_node_t, parser->result_stack_alloc);

    // work out the top-level rule to use, and push it on the stack
    int top_level_rule;
    switch (input_kind) {
        case MP_PARSE_SINGLE_INPUT: top_level_rule = RULE_single_input; break;
        //case MP_PARSE_EVAL_INPUT: top_level_rule = RULE_eval_input; break;
        default: top_level_rule = RULE_file_input;
    }
    push_rule(parser, rules[top_level_rule], 0);

    // parse!

    uint n, i;
    bool backtrack = false;
    const rule_t *rule;
    mp_token_kind_t tok_kind;
    bool emit_rule;
    bool had_trailing_sep;

    for (;;) {
        next_rule:
        if (parser->rule_stack_top == 0) {
            break;
        }

        pop_rule(parser, &rule, &i);
        n = rule->act & RULE_ACT_ARG_MASK;

        /*
        // debugging
        printf("depth=%d ", parser->rule_stack_top);
        for (int j = 0; j < parser->rule_stack_top; ++j) {
            printf(" ");
        }
        printf("%s n=%d i=%d bt=%d\n", rule->rule_name, n, i, backtrack);
        */

        switch (rule->act & RULE_ACT_KIND_MASK) {
            case RULE_ACT_OR:
                if (i > 0 && !backtrack) {
                    goto next_rule;
                } else {
                    backtrack = false;
                }
                for (; i < n - 1; ++i) {
                    switch (rule->arg[i] & RULE_ARG_KIND_MASK) {
                        case RULE_ARG_TOK:
                            if (mp_lexer_is_kind(lex, rule->arg[i] & RULE_ARG_ARG_MASK)) {
                                push_result_token(parser, lex);
                                mp_lexer_to_next(lex);
                                goto next_rule;
                            }
                            break;
                        case RULE_ARG_RULE:
                            push_rule(parser, rule, i + 1);
                            push_rule_from_arg(parser, rule->arg[i]);
                            goto next_rule;
                        default:
                            assert(0);
                    }
                }
                if ((rule->arg[i] & RULE_ARG_KIND_MASK) == RULE_ARG_TOK) {
                    if (mp_lexer_is_kind(lex, rule->arg[i] & RULE_ARG_ARG_MASK)) {
                        push_result_token(parser, lex);
                        mp_lexer_to_next(lex);
                    } else {
                        backtrack = true;
                        goto next_rule;
                    }
                } else {
                    push_rule_from_arg(parser, rule->arg[i]);
                }
                break;

            case RULE_ACT_AND:

                // failed, backtrack if we can, else syntax error
                if (backtrack) {
                    assert(i > 0);
                    if ((rule->arg[i - 1] & RULE_ARG_KIND_MASK) == RULE_ARG_OPT_RULE) {
                        // an optional rule that failed, so continue with next arg
                        push_result_node(parser, MP_PARSE_NODE_NULL);
                        backtrack = false;
                    } else {
                        // a mandatory rule that failed, so propagate backtrack
                        if (i > 1) {
                            // already eaten tokens so can't backtrack
                            goto syntax_error;
                        } else {
                            goto next_rule;
                        }
                    }
                }

                // progress through the rule
                for (; i < n; ++i) {
                    switch (rule->arg[i] & RULE_ARG_KIND_MASK) {
                        case RULE_ARG_TOK:
                            // need to match a token
                            tok_kind = rule->arg[i] & RULE_ARG_ARG_MASK;
                            if (mp_lexer_is_kind(lex, tok_kind)) {
                                // matched token
                                if (tok_kind == MP_TOKEN_NAME) {
                                    push_result_token(parser, lex);
                                }
                                mp_lexer_to_next(lex);
                            } else {
                                // failed to match token
                                if (i > 0) {
                                    // already eaten tokens so can't backtrack
                                    goto syntax_error;
                                } else {
                                    // this rule failed, so backtrack
                                    backtrack = true;
                                    goto next_rule;
                                }
                            }
                            break;
                        case RULE_ARG_RULE:
                            //if (i + 1 < n) {
                                push_rule(parser, rule, i + 1);
                            //}
                            push_rule_from_arg(parser, rule->arg[i]);
                            goto next_rule;
                        case RULE_ARG_OPT_RULE:
                            push_rule(parser, rule, i + 1);
                            push_rule_from_arg(parser, rule->arg[i]);
                            goto next_rule;
                        default:
                            assert(0);
                    }
                }

                assert(i == n);

                // matched the rule, so now build the corresponding parse_node

                // count number of arguments for the parse_node
                i = 0;
                emit_rule = false;
                for (int x = 0; x < n; ++x) {
                    if ((rule->arg[x] & RULE_ARG_KIND_MASK) == RULE_ARG_TOK) {
                        tok_kind = rule->arg[x] & RULE_ARG_ARG_MASK;
                        if (tok_kind >= MP_TOKEN_NAME) {
                            emit_rule = true;
                        }
                        if (tok_kind == MP_TOKEN_NAME) {
                            // only tokens which were names are pushed to stack
                            i += 1;
                        }
                    } else {
                        // rules are always pushed
                        i += 1;
                    }
                }

                // always emit these rules, even if they have only 1 argument
                if (rule->rule_id == RULE_expr_stmt || rule->rule_id == RULE_yield_stmt) {
                    emit_rule = true;
                }

                // never emit these rules if they have only 1 argument
                // NOTE: can't put atom_paren here because we need it to distinguisg, for example, [a,b] from [(a,b)]
                // TODO possibly put varargslist_name, varargslist_equal here as well
                if (rule->rule_id == RULE_else_stmt || rule->rule_id == RULE_testlist_comp_3b || rule->rule_id == RULE_import_as_names_paren || rule->rule_id == RULE_typedargslist_name || rule->rule_id == RULE_typedargslist_colon || rule->rule_id == RULE_typedargslist_equal || rule->rule_id == RULE_dictorsetmaker_colon || rule->rule_id == RULE_classdef_2 || rule->rule_id == RULE_with_item_as || rule->rule_id == RULE_assert_stmt_extra || rule->rule_id == RULE_as_name || rule->rule_id == RULE_raise_stmt_from || rule->rule_id == RULE_vfpdef) {
                    emit_rule = false;
                }

                // always emit these rules, and add an extra blank node at the end (to be used by the compiler to store data)
                if (rule->rule_id == RULE_funcdef || rule->rule_id == RULE_classdef || rule->rule_id == RULE_comp_for || rule->rule_id == RULE_lambdef || rule->rule_id == RULE_lambdef_nocond) {
                    emit_rule = true;
                    push_result_node(parser, MP_PARSE_NODE_NULL);
                    i += 1;
                }

                int num_not_nil = 0;
                for (int x = 0; x < i; ++x) {
                    if (peek_result(parser, x) != MP_PARSE_NODE_NULL) {
                        num_not_nil += 1;
                    }
                }
                //printf("done and %s n=%d i=%d notnil=%d\n", rule->rule_name, n, i, num_not_nil);
                if (emit_rule) {
                    push_result_rule(parser, rule, i);
                } else if (num_not_nil == 0) {
                    push_result_rule(parser, rule, i); // needed for, eg, atom_paren, testlist_comp_3b
                    //result_stack_show(parser);
                    //assert(0);
                } else if (num_not_nil == 1) {
                    // single result, leave it on stack
                    mp_parse_node_t pn = MP_PARSE_NODE_NULL;
                    for (int x = 0; x < i; ++x) {
                        mp_parse_node_t pn2 = pop_result(parser);
                        if (pn2 != MP_PARSE_NODE_NULL) {
                            pn = pn2;
                        }
                    }
                    push_result_node(parser, pn);
                } else {
                    push_result_rule(parser, rule, i);
                }
                break;

            case RULE_ACT_LIST:
                // n=2 is: item item*
                // n=1 is: item (sep item)*
                // n=3 is: item (sep item)* [sep]
                if (backtrack) {
                    list_backtrack:
                    had_trailing_sep = false;
                    if (n == 2) {
                        if (i == 1) {
                            // fail on item, first time round; propagate backtrack
                            goto next_rule;
                        } else {
                            // fail on item, in later rounds; finish with this rule
                            backtrack = false;
                        }
                    } else {
                        if (i == 1) {
                            // fail on item, first time round; propagate backtrack
                            goto next_rule;
                        } else if ((i & 1) == 1) {
                            // fail on item, in later rounds; have eaten tokens so can't backtrack
                            if (n == 3) {
                                // list allows trailing separator; finish parsing list
                                had_trailing_sep = true;
                                backtrack = false;
                            } else {
                                // list doesn't allowing trailing separator; fail
                                goto syntax_error;
                            }
                        } else {
                            // fail on separator; finish parsing list
                            backtrack = false;
                        }
                    }
                } else {
                    for (;;) {
                        uint arg = rule->arg[i & 1 & n];
                        switch (arg & RULE_ARG_KIND_MASK) {
                            case RULE_ARG_TOK:
                                if (mp_lexer_is_kind(lex, arg & RULE_ARG_ARG_MASK)) {
                                    if (i & 1 & n) {
                                        // separators which are tokens are not pushed to result stack
                                    } else {
                                        push_result_token(parser, lex);
                                    }
                                    mp_lexer_to_next(lex);
                                    // got element of list, so continue parsing list
                                    i += 1;
                                } else {
                                    // couldn't get element of list
                                    i += 1;
                                    backtrack = true;
                                    goto list_backtrack;
                                }
                                break;
                            case RULE_ARG_RULE:
                                push_rule(parser, rule, i + 1);
                                push_rule_from_arg(parser, arg);
                                goto next_rule;
                            default:
                                assert(0);
                        }
                    }
                }
                assert(i >= 1);

                // compute number of elements in list, result in i
                i -= 1;
                if ((n & 1) && (rule->arg[1] & RULE_ARG_KIND_MASK) == RULE_ARG_TOK) {
                    // don't count separators when they are tokens
                    i = (i + 1) / 2;
                }

                if (i == 1) {
                    // list matched single item
                    if (had_trailing_sep) {
                        // if there was a trailing separator, make a list of a single item
                        push_result_rule(parser, rule, i);
                    } else {
                        // just leave single item on stack (ie don't wrap in a list)
                    }
                } else {
                    //printf("done list %s %d %d\n", rule->rule_name, n, i);
                    push_result_rule(parser, rule, i);
                }
                break;

            default:
                assert(0);
        }
    }

    // check we are at the end of the token stream
    if (!mp_lexer_is_kind(lex, MP_TOKEN_END)) {
        goto syntax_error;
    }

    //printf("--------------\n");
    //result_stack_show(parser);
    //printf("rule stack alloc: %d\n", parser->rule_stack_alloc);
    //printf("result stack alloc: %d\n", parser->result_stack_alloc);
    //printf("number of parse nodes allocated: %d\n", num_parse_nodes_allocated);

    // get the root parse node that we created
    assert(parser->result_stack_top == 1);
    mp_parse_node_t result = parser->result_stack[0];

finished:
    // free the memory that we don't need anymore
    m_del(rule_stack_t, parser->rule_stack, parser->rule_stack_alloc);
    m_del(mp_parse_node_t, parser->result_stack, parser->result_stack_alloc);
    m_del_obj(parser_t, parser);

    // return the result
    return result;

syntax_error:
    // TODO these should raise a proper exception
    if (mp_lexer_is_kind(lex, MP_TOKEN_INDENT)) {
        mp_lexer_show_error_pythonic(lex, "IndentationError: unexpected indent");
    } else if (mp_lexer_is_kind(lex, MP_TOKEN_DEDENT_MISMATCH)) {
        mp_lexer_show_error_pythonic(lex, "IndentationError: unindent does not match any outer indentation level");
    } else {
        mp_lexer_show_error_pythonic(lex, "syntax error:");
#ifdef USE_RULE_NAME
        mp_lexer_show_error(lex, rule->rule_name);
#endif
        mp_token_show(mp_lexer_cur(lex));
    }
    result = MP_PARSE_NODE_NULL;
    goto finished;
}
Exemplo n.º 8
0
mp_parse_tree_t mp_parse(mp_lexer_t *lex, mp_parse_input_kind_t input_kind) {

    // initialise parser and allocate memory for its stacks

    parser_t parser;

    parser.rule_stack_alloc = MICROPY_ALLOC_PARSE_RULE_INIT;
    parser.rule_stack_top = 0;
    parser.rule_stack = m_new(rule_stack_t, parser.rule_stack_alloc);

    parser.result_stack_alloc = MICROPY_ALLOC_PARSE_RESULT_INIT;
    parser.result_stack_top = 0;
    parser.result_stack = m_new(mp_parse_node_t, parser.result_stack_alloc);

    parser.lexer = lex;

    parser.tree.chunk = NULL;
    parser.cur_chunk = NULL;

    #if MICROPY_COMP_CONST
    mp_map_init(&parser.consts, 0);
    #endif

    // work out the top-level rule to use, and push it on the stack
    size_t top_level_rule;
    switch (input_kind) {
        case MP_PARSE_SINGLE_INPUT: top_level_rule = RULE_single_input; break;
        case MP_PARSE_EVAL_INPUT: top_level_rule = RULE_eval_input; break;
        default: top_level_rule = RULE_file_input;
    }
    push_rule(&parser, lex->tok_line, rules[top_level_rule], 0);

    // parse!

    size_t n, i; // state for the current rule
    size_t rule_src_line; // source line for the first token matched by the current rule
    bool backtrack = false;
    const rule_t *rule = NULL;

    for (;;) {
        next_rule:
        if (parser.rule_stack_top == 0) {
            break;
        }

        pop_rule(&parser, &rule, &i, &rule_src_line);
        n = rule->act & RULE_ACT_ARG_MASK;

        /*
        // debugging
        printf("depth=%d ", parser.rule_stack_top);
        for (int j = 0; j < parser.rule_stack_top; ++j) {
            printf(" ");
        }
        printf("%s n=%d i=%d bt=%d\n", rule->rule_name, n, i, backtrack);
        */

        switch (rule->act & RULE_ACT_KIND_MASK) {
            case RULE_ACT_OR:
                if (i > 0 && !backtrack) {
                    goto next_rule;
                } else {
                    backtrack = false;
                }
                for (; i < n; ++i) {
                    uint16_t kind = rule->arg[i] & RULE_ARG_KIND_MASK;
                    if (kind == RULE_ARG_TOK) {
                        if (lex->tok_kind == (rule->arg[i] & RULE_ARG_ARG_MASK)) {
                            push_result_token(&parser, rule);
                            mp_lexer_to_next(lex);
                            goto next_rule;
                        }
                    } else {
                        assert(kind == RULE_ARG_RULE);
                        if (i + 1 < n) {
                            push_rule(&parser, rule_src_line, rule, i + 1); // save this or-rule
                        }
                        push_rule_from_arg(&parser, rule->arg[i]); // push child of or-rule
                        goto next_rule;
                    }
                }
                backtrack = true;
                break;

            case RULE_ACT_AND: {

                // failed, backtrack if we can, else syntax error
                if (backtrack) {
                    assert(i > 0);
                    if ((rule->arg[i - 1] & RULE_ARG_KIND_MASK) == RULE_ARG_OPT_RULE) {
                        // an optional rule that failed, so continue with next arg
                        push_result_node(&parser, MP_PARSE_NODE_NULL);
                        backtrack = false;
                    } else {
                        // a mandatory rule that failed, so propagate backtrack
                        if (i > 1) {
                            // already eaten tokens so can't backtrack
                            goto syntax_error;
                        } else {
                            goto next_rule;
                        }
                    }
                }

                // progress through the rule
                for (; i < n; ++i) {
                    if ((rule->arg[i] & RULE_ARG_KIND_MASK) == RULE_ARG_TOK) {
                        // need to match a token
                        mp_token_kind_t tok_kind = rule->arg[i] & RULE_ARG_ARG_MASK;
                        if (lex->tok_kind == tok_kind) {
                            // matched token
                            if (tok_kind == MP_TOKEN_NAME) {
                                push_result_token(&parser, rule);
                            }
                            mp_lexer_to_next(lex);
                        } else {
                            // failed to match token
                            if (i > 0) {
                                // already eaten tokens so can't backtrack
                                goto syntax_error;
                            } else {
                                // this rule failed, so backtrack
                                backtrack = true;
                                goto next_rule;
                            }
                        }
                    } else {
                        push_rule(&parser, rule_src_line, rule, i + 1); // save this and-rule
                        push_rule_from_arg(&parser, rule->arg[i]); // push child of and-rule
                        goto next_rule;
                    }
                }

                assert(i == n);

                // matched the rule, so now build the corresponding parse_node

                #if !MICROPY_ENABLE_DOC_STRING
                // this code discards lonely statements, such as doc strings
                if (input_kind != MP_PARSE_SINGLE_INPUT && rule->rule_id == RULE_expr_stmt && peek_result(&parser, 0) == MP_PARSE_NODE_NULL) {
                    mp_parse_node_t p = peek_result(&parser, 1);
                    if ((MP_PARSE_NODE_IS_LEAF(p) && !MP_PARSE_NODE_IS_ID(p))
                        || MP_PARSE_NODE_IS_STRUCT_KIND(p, RULE_const_object)) {
                        pop_result(&parser); // MP_PARSE_NODE_NULL
                        pop_result(&parser); // const expression (leaf or RULE_const_object)
                        // Pushing the "pass" rule here will overwrite any RULE_const_object
                        // entry that was on the result stack, allowing the GC to reclaim
                        // the memory from the const object when needed.
                        push_result_rule(&parser, rule_src_line, rules[RULE_pass_stmt], 0);
                        break;
                    }
                }
                #endif

                // count number of arguments for the parse node
                i = 0;
                size_t num_not_nil = 0;
                for (size_t x = n; x > 0;) {
                    --x;
                    if ((rule->arg[x] & RULE_ARG_KIND_MASK) == RULE_ARG_TOK) {
                        mp_token_kind_t tok_kind = rule->arg[x] & RULE_ARG_ARG_MASK;
                        if (tok_kind == MP_TOKEN_NAME) {
                            // only tokens which were names are pushed to stack
                            i += 1;
                            num_not_nil += 1;
                        }
                    } else {
                        // rules are always pushed
                        if (peek_result(&parser, i) != MP_PARSE_NODE_NULL) {
                            num_not_nil += 1;
                        }
                        i += 1;
                    }
                }

                if (num_not_nil == 1 && (rule->act & RULE_ACT_ALLOW_IDENT)) {
                    // this rule has only 1 argument and should not be emitted
                    mp_parse_node_t pn = MP_PARSE_NODE_NULL;
                    for (size_t x = 0; x < i; ++x) {
                        mp_parse_node_t pn2 = pop_result(&parser);
                        if (pn2 != MP_PARSE_NODE_NULL) {
                            pn = pn2;
                        }
                    }
                    push_result_node(&parser, pn);
                } else {
                    // this rule must be emitted

                    if (rule->act & RULE_ACT_ADD_BLANK) {
                        // and add an extra blank node at the end (used by the compiler to store data)
                        push_result_node(&parser, MP_PARSE_NODE_NULL);
                        i += 1;
                    }

                    push_result_rule(&parser, rule_src_line, rule, i);
                }
                break;
            }

            default: {
                assert((rule->act & RULE_ACT_KIND_MASK) == RULE_ACT_LIST);

                // n=2 is: item item*
                // n=1 is: item (sep item)*
                // n=3 is: item (sep item)* [sep]
                bool had_trailing_sep;
                if (backtrack) {
                    list_backtrack:
                    had_trailing_sep = false;
                    if (n == 2) {
                        if (i == 1) {
                            // fail on item, first time round; propagate backtrack
                            goto next_rule;
                        } else {
                            // fail on item, in later rounds; finish with this rule
                            backtrack = false;
                        }
                    } else {
                        if (i == 1) {
                            // fail on item, first time round; propagate backtrack
                            goto next_rule;
                        } else if ((i & 1) == 1) {
                            // fail on item, in later rounds; have eaten tokens so can't backtrack
                            if (n == 3) {
                                // list allows trailing separator; finish parsing list
                                had_trailing_sep = true;
                                backtrack = false;
                            } else {
                                // list doesn't allowing trailing separator; fail
                                goto syntax_error;
                            }
                        } else {
                            // fail on separator; finish parsing list
                            backtrack = false;
                        }
                    }
                } else {
                    for (;;) {
                        size_t arg = rule->arg[i & 1 & n];
                        if ((arg & RULE_ARG_KIND_MASK) == RULE_ARG_TOK) {
                            if (lex->tok_kind == (arg & RULE_ARG_ARG_MASK)) {
                                if (i & 1 & n) {
                                    // separators which are tokens are not pushed to result stack
                                } else {
                                    push_result_token(&parser, rule);
                                }
                                mp_lexer_to_next(lex);
                                // got element of list, so continue parsing list
                                i += 1;
                            } else {
                                // couldn't get element of list
                                i += 1;
                                backtrack = true;
                                goto list_backtrack;
                            }
                        } else {
                            assert((arg & RULE_ARG_KIND_MASK) == RULE_ARG_RULE);
                            push_rule(&parser, rule_src_line, rule, i + 1); // save this list-rule
                            push_rule_from_arg(&parser, arg); // push child of list-rule
                            goto next_rule;
                        }
                    }
                }
                assert(i >= 1);

                // compute number of elements in list, result in i
                i -= 1;
                if ((n & 1) && (rule->arg[1] & RULE_ARG_KIND_MASK) == RULE_ARG_TOK) {
                    // don't count separators when they are tokens
                    i = (i + 1) / 2;
                }

                if (i == 1) {
                    // list matched single item
                    if (had_trailing_sep) {
                        // if there was a trailing separator, make a list of a single item
                        push_result_rule(&parser, rule_src_line, rule, i);
                    } else {
                        // just leave single item on stack (ie don't wrap in a list)
                    }
                } else {
                    push_result_rule(&parser, rule_src_line, rule, i);
                }
                break;
            }
        }
    }

    #if MICROPY_COMP_CONST
    mp_map_deinit(&parser.consts);
    #endif

    // truncate final chunk and link into chain of chunks
    if (parser.cur_chunk != NULL) {
        (void)m_renew_maybe(byte, parser.cur_chunk,
            sizeof(mp_parse_chunk_t) + parser.cur_chunk->alloc,
            sizeof(mp_parse_chunk_t) + parser.cur_chunk->union_.used,
            false);
        parser.cur_chunk->alloc = parser.cur_chunk->union_.used;
        parser.cur_chunk->union_.next = parser.tree.chunk;
        parser.tree.chunk = parser.cur_chunk;
    }

    if (
        lex->tok_kind != MP_TOKEN_END // check we are at the end of the token stream
        || parser.result_stack_top == 0 // check that we got a node (can fail on empty input)
        ) {
    syntax_error:;
        mp_obj_t exc;
        if (lex->tok_kind == MP_TOKEN_INDENT) {
            exc = mp_obj_new_exception_msg(&mp_type_IndentationError,
                "unexpected indent");
        } else if (lex->tok_kind == MP_TOKEN_DEDENT_MISMATCH) {
            exc = mp_obj_new_exception_msg(&mp_type_IndentationError,
                "unindent does not match any outer indentation level");
        } else {
            exc = mp_obj_new_exception_msg(&mp_type_SyntaxError,
                "invalid syntax");
        }
        // add traceback to give info about file name and location
        // we don't have a 'block' name, so just pass the NULL qstr to indicate this
        mp_obj_exception_add_traceback(exc, lex->source_name, lex->tok_line, MP_QSTR_NULL);
        nlr_raise(exc);
    }

    // get the root parse node that we created
    assert(parser.result_stack_top == 1);
    parser.tree.root = parser.result_stack[0];

    // free the memory that we don't need anymore
    m_del(rule_stack_t, parser.rule_stack, parser.rule_stack_alloc);
    m_del(mp_parse_node_t, parser.result_stack, parser.result_stack_alloc);

    // we also free the lexer on behalf of the caller
    mp_lexer_free(lex);

    return parser.tree;
}
Exemplo n.º 9
0
// returns standard error codes: 0 for success, 1 for all other errors
STATIC int execute_from_lexer(mp_lexer_t *lex, mp_parse_input_kind_t input_kind, bool is_repl) {
    if (lex == NULL) {
        return 1;
    }

    if (0) {
        // just tokenise
        while (!mp_lexer_is_kind(lex, MP_TOKEN_END)) {
            mp_token_show(mp_lexer_cur(lex));
            mp_lexer_to_next(lex);
        }
        mp_lexer_free(lex);
        return 0;
    }

    mp_parse_error_kind_t parse_error_kind;
    mp_parse_node_t pn = mp_parse(lex, input_kind, &parse_error_kind);

    if (pn == MP_PARSE_NODE_NULL) {
        // parse error
        mp_parse_show_exception(lex, parse_error_kind);
        mp_lexer_free(lex);
        return 1;
    }

    qstr source_name = mp_lexer_source_name(lex);
    #if MICROPY_PY___FILE__
    if (input_kind == MP_PARSE_FILE_INPUT) {
        mp_store_global(MP_QSTR___file__, MP_OBJ_NEW_QSTR(source_name));
    }
    #endif
    mp_lexer_free(lex);

    /*
    printf("----------------\n");
    mp_parse_node_print(pn, 0);
    printf("----------------\n");
    */

    mp_obj_t module_fun = mp_compile(pn, source_name, emit_opt, is_repl);

    if (module_fun == mp_const_none) {
        // compile error
        return 1;
    }

    if (compile_only) {
        return 0;
    }

    // execute it
    nlr_buf_t nlr;
    if (nlr_push(&nlr) == 0) {
        mp_call_function_0(module_fun);
        nlr_pop();
        return 0;
    } else {
        // uncaught exception
        // check for SystemExit
        mp_obj_t exc = (mp_obj_t)nlr.ret_val;
        if (mp_obj_is_subclass_fast(mp_obj_get_type(exc), &mp_type_SystemExit)) {
            mp_obj_t exit_val = mp_obj_exception_get_value(exc);
            mp_int_t val;
            if (!mp_obj_get_int_maybe(exit_val, &val)) {
                val = 0;
            }
            exit(val);
        }
        mp_obj_print_exception((mp_obj_t)nlr.ret_val);
        return 1;
    }
}
Exemplo n.º 10
0
mp_parse_tree_t mp_parse(mp_lexer_t *lex, mp_parse_input_kind_t input_kind) {

    // initialise parser and allocate memory for its stacks

    parser_t parser;

    parser.parse_error = PARSE_ERROR_NONE;

    parser.rule_stack_alloc = MICROPY_ALLOC_PARSE_RULE_INIT;
    parser.rule_stack_top = 0;
    parser.rule_stack = m_new_maybe(rule_stack_t, parser.rule_stack_alloc);

    parser.result_stack_alloc = MICROPY_ALLOC_PARSE_RESULT_INIT;
    parser.result_stack_top = 0;
    parser.result_stack = m_new_maybe(mp_parse_node_t, parser.result_stack_alloc);

    parser.lexer = lex;

    parser.tree.chunk = NULL;
    parser.cur_chunk = NULL;

    #if MICROPY_COMP_CONST
    mp_map_init(&parser.consts, 0);
    #endif

    // check if we could allocate the stacks
    if (parser.rule_stack == NULL || parser.result_stack == NULL) {
        goto memory_error;
    }

    // work out the top-level rule to use, and push it on the stack
    size_t top_level_rule;
    switch (input_kind) {
        case MP_PARSE_SINGLE_INPUT: top_level_rule = RULE_single_input; break;
        case MP_PARSE_EVAL_INPUT: top_level_rule = RULE_eval_input; break;
        default: top_level_rule = RULE_file_input;
    }
    push_rule(&parser, lex->tok_line, rules[top_level_rule], 0);

    // parse!

    size_t n, i; // state for the current rule
    size_t rule_src_line; // source line for the first token matched by the current rule
    bool backtrack = false;
    const rule_t *rule = NULL;

    for (;;) {
        next_rule:
        if (parser.rule_stack_top == 0 || parser.parse_error) {
            break;
        }

        pop_rule(&parser, &rule, &i, &rule_src_line);
        n = rule->act & RULE_ACT_ARG_MASK;

        /*
        // debugging
        printf("depth=%d ", parser.rule_stack_top);
        for (int j = 0; j < parser.rule_stack_top; ++j) {
            printf(" ");
        }
        printf("%s n=%d i=%d bt=%d\n", rule->rule_name, n, i, backtrack);
        */

        switch (rule->act & RULE_ACT_KIND_MASK) {
            case RULE_ACT_OR:
                if (i > 0 && !backtrack) {
                    goto next_rule;
                } else {
                    backtrack = false;
                }
                for (; i < n; ++i) {
                    uint16_t kind = rule->arg[i] & RULE_ARG_KIND_MASK;
                    if (kind == RULE_ARG_TOK) {
                        if (lex->tok_kind == (rule->arg[i] & RULE_ARG_ARG_MASK)) {
                            push_result_token(&parser);
                            mp_lexer_to_next(lex);
                            goto next_rule;
                        }
                    } else {
                        assert(kind == RULE_ARG_RULE);
                        if (i + 1 < n) {
                            push_rule(&parser, rule_src_line, rule, i + 1); // save this or-rule
                        }
                        push_rule_from_arg(&parser, rule->arg[i]); // push child of or-rule
                        goto next_rule;
                    }
                }
                backtrack = true;
                break;

            case RULE_ACT_AND: {

                // failed, backtrack if we can, else syntax error
                if (backtrack) {
                    assert(i > 0);
                    if ((rule->arg[i - 1] & RULE_ARG_KIND_MASK) == RULE_ARG_OPT_RULE) {
                        // an optional rule that failed, so continue with next arg
                        push_result_node(&parser, MP_PARSE_NODE_NULL);
                        backtrack = false;
                    } else {
                        // a mandatory rule that failed, so propagate backtrack
                        if (i > 1) {
                            // already eaten tokens so can't backtrack
                            goto syntax_error;
                        } else {
                            goto next_rule;
                        }
                    }
                }

                // progress through the rule
                for (; i < n; ++i) {
                    switch (rule->arg[i] & RULE_ARG_KIND_MASK) {
                        case RULE_ARG_TOK: {
                            // need to match a token
                            mp_token_kind_t tok_kind = rule->arg[i] & RULE_ARG_ARG_MASK;
                            if (lex->tok_kind == tok_kind) {
                                // matched token
                                if (tok_kind == MP_TOKEN_NAME) {
                                    push_result_token(&parser);
                                }
                                mp_lexer_to_next(lex);
                            } else {
                                // failed to match token
                                if (i > 0) {
                                    // already eaten tokens so can't backtrack
                                    goto syntax_error;
                                } else {
                                    // this rule failed, so backtrack
                                    backtrack = true;
                                    goto next_rule;
                                }
                            }
                            break;
                        }
                        case RULE_ARG_RULE:
                        case RULE_ARG_OPT_RULE:
                        rule_and_no_other_choice:
                            push_rule(&parser, rule_src_line, rule, i + 1); // save this and-rule
                            push_rule_from_arg(&parser, rule->arg[i]); // push child of and-rule
                            goto next_rule;
                        default:
                            assert(0);
                            goto rule_and_no_other_choice; // to help flow control analysis
                    }
                }

                assert(i == n);

                // matched the rule, so now build the corresponding parse_node

                #if !MICROPY_ENABLE_DOC_STRING
                // this code discards lonely statements, such as doc strings
                if (input_kind != MP_PARSE_SINGLE_INPUT && rule->rule_id == RULE_expr_stmt && peek_result(&parser, 0) == MP_PARSE_NODE_NULL) {
                    mp_parse_node_t p = peek_result(&parser, 1);
                    if ((MP_PARSE_NODE_IS_LEAF(p) && !MP_PARSE_NODE_IS_ID(p)) || MP_PARSE_NODE_IS_STRUCT_KIND(p, RULE_string)) {
                        pop_result(&parser); // MP_PARSE_NODE_NULL
                        mp_parse_node_t pn = pop_result(&parser); // possibly RULE_string
                        if (MP_PARSE_NODE_IS_STRUCT(pn)) {
                            mp_parse_node_struct_t *pns = (mp_parse_node_struct_t *)pn;
                            if (MP_PARSE_NODE_STRUCT_KIND(pns) == RULE_string) {
                                m_del(char, (char*)pns->nodes[0], (size_t)pns->nodes[1]);
                            }
                        }
                        push_result_rule(&parser, rule_src_line, rules[RULE_pass_stmt], 0);
                        break;
                    }
                }
                #endif

                // count number of arguments for the parse node
                i = 0;
                size_t num_not_nil = 0;
                for (size_t x = n; x > 0;) {
                    --x;
                    if ((rule->arg[x] & RULE_ARG_KIND_MASK) == RULE_ARG_TOK) {
                        mp_token_kind_t tok_kind = rule->arg[x] & RULE_ARG_ARG_MASK;
                        if (tok_kind == MP_TOKEN_NAME) {
                            // only tokens which were names are pushed to stack
                            i += 1;
                            num_not_nil += 1;
                        }
                    } else {
                        // rules are always pushed
                        if (peek_result(&parser, i) != MP_PARSE_NODE_NULL) {
                            num_not_nil += 1;
                        }
                        i += 1;
                    }
                }

                if (num_not_nil == 1 && (rule->act & RULE_ACT_ALLOW_IDENT)) {
                    // this rule has only 1 argument and should not be emitted
                    mp_parse_node_t pn = MP_PARSE_NODE_NULL;
                    for (size_t x = 0; x < i; ++x) {
                        mp_parse_node_t pn2 = pop_result(&parser);
                        if (pn2 != MP_PARSE_NODE_NULL) {
                            pn = pn2;
                        }
                    }
                    push_result_node(&parser, pn);
                } else {
                    // this rule must be emitted

                    if (rule->act & RULE_ACT_ADD_BLANK) {
                        // and add an extra blank node at the end (used by the compiler to store data)
                        push_result_node(&parser, MP_PARSE_NODE_NULL);
                        i += 1;
                    }

                    push_result_rule(&parser, rule_src_line, rule, i);
                }
                break;
            }
Exemplo n.º 11
0
mp_parse_node_t mp_parse(mp_lexer_t *lex, mp_parse_input_kind_t input_kind, mp_parse_error_kind_t *parse_error_kind_out) {

    // initialise parser and allocate memory for its stacks

    parser_t parser;

    parser.had_memory_error = false;

    parser.rule_stack_alloc = MICROPY_ALLOC_PARSE_RULE_INIT;
    parser.rule_stack_top = 0;
    parser.rule_stack = m_new_maybe(rule_stack_t, parser.rule_stack_alloc);

    parser.result_stack_alloc = MICROPY_ALLOC_PARSE_RESULT_INIT;
    parser.result_stack_top = 0;
    parser.result_stack = m_new_maybe(mp_parse_node_t, parser.result_stack_alloc);

    parser.lexer = lex;

    // check if we could allocate the stacks
    if (parser.rule_stack == NULL || parser.result_stack == NULL) {
        goto memory_error;
    }

    // work out the top-level rule to use, and push it on the stack
    int top_level_rule;
    switch (input_kind) {
        case MP_PARSE_SINGLE_INPUT: top_level_rule = RULE_single_input; break;
        case MP_PARSE_EVAL_INPUT: top_level_rule = RULE_eval_input; break;
        default: top_level_rule = RULE_file_input;
    }
    push_rule(&parser, mp_lexer_cur(lex)->src_line, rules[top_level_rule], 0);

    // parse!

    uint n, i; // state for the current rule
    uint rule_src_line; // source line for the first token matched by the current rule
    bool backtrack = false;
    const rule_t *rule = NULL;
    mp_token_kind_t tok_kind;
    bool emit_rule;
    bool had_trailing_sep;

    for (;;) {
        next_rule:
        if (parser.rule_stack_top == 0 || parser.had_memory_error) {
            break;
        }

        pop_rule(&parser, &rule, &i, &rule_src_line);
        n = rule->act & RULE_ACT_ARG_MASK;

        /*
        // debugging
        printf("depth=%d ", parser.rule_stack_top);
        for (int j = 0; j < parser.rule_stack_top; ++j) {
            printf(" ");
        }
        printf("%s n=%d i=%d bt=%d\n", rule->rule_name, n, i, backtrack);
        */

        switch (rule->act & RULE_ACT_KIND_MASK) {
            case RULE_ACT_OR:
                if (i > 0 && !backtrack) {
                    goto next_rule;
                } else {
                    backtrack = false;
                }
                for (; i < n - 1; ++i) {
                    switch (rule->arg[i] & RULE_ARG_KIND_MASK) {
                        case RULE_ARG_TOK:
                            if (mp_lexer_is_kind(lex, rule->arg[i] & RULE_ARG_ARG_MASK)) {
                                push_result_token(&parser, lex);
                                mp_lexer_to_next(lex);
                                goto next_rule;
                            }
                            break;
                        case RULE_ARG_RULE:
                            push_rule(&parser, rule_src_line, rule, i + 1); // save this or-rule
                            push_rule_from_arg(&parser, rule->arg[i]); // push child of or-rule
                            goto next_rule;
                        default:
                            assert(0);
                    }
                }
                if ((rule->arg[i] & RULE_ARG_KIND_MASK) == RULE_ARG_TOK) {
                    if (mp_lexer_is_kind(lex, rule->arg[i] & RULE_ARG_ARG_MASK)) {
                        push_result_token(&parser, lex);
                        mp_lexer_to_next(lex);
                    } else {
                        backtrack = true;
                        goto next_rule;
                    }
                } else {
                    push_rule_from_arg(&parser, rule->arg[i]);
                }
                break;

            case RULE_ACT_AND:

                // failed, backtrack if we can, else syntax error
                if (backtrack) {
                    assert(i > 0);
                    if ((rule->arg[i - 1] & RULE_ARG_KIND_MASK) == RULE_ARG_OPT_RULE) {
                        // an optional rule that failed, so continue with next arg
                        push_result_node(&parser, MP_PARSE_NODE_NULL);
                        backtrack = false;
                    } else {
                        // a mandatory rule that failed, so propagate backtrack
                        if (i > 1) {
                            // already eaten tokens so can't backtrack
                            goto syntax_error;
                        } else {
                            goto next_rule;
                        }
                    }
                }

                // progress through the rule
                for (; i < n; ++i) {
                    switch (rule->arg[i] & RULE_ARG_KIND_MASK) {
                        case RULE_ARG_TOK:
                            // need to match a token
                            tok_kind = rule->arg[i] & RULE_ARG_ARG_MASK;
                            if (mp_lexer_is_kind(lex, tok_kind)) {
                                // matched token
                                if (tok_kind == MP_TOKEN_NAME) {
                                    push_result_token(&parser, lex);
                                }
                                mp_lexer_to_next(lex);
                            } else {
                                // failed to match token
                                if (i > 0) {
                                    // already eaten tokens so can't backtrack
                                    goto syntax_error;
                                } else {
                                    // this rule failed, so backtrack
                                    backtrack = true;
                                    goto next_rule;
                                }
                            }
                            break;
                        case RULE_ARG_RULE:
                        case RULE_ARG_OPT_RULE:
                            push_rule(&parser, rule_src_line, rule, i + 1); // save this and-rule
                            push_rule_from_arg(&parser, rule->arg[i]); // push child of and-rule
                            goto next_rule;
                        default:
                            assert(0);
                    }
                }

                assert(i == n);

                // matched the rule, so now build the corresponding parse_node

                // count number of arguments for the parse_node
                i = 0;
                emit_rule = false;
                for (int x = 0; x < n; ++x) {
                    if ((rule->arg[x] & RULE_ARG_KIND_MASK) == RULE_ARG_TOK) {
                        tok_kind = rule->arg[x] & RULE_ARG_ARG_MASK;
                        if (tok_kind >= MP_TOKEN_NAME) {
                            emit_rule = true;
                        }
                        if (tok_kind == MP_TOKEN_NAME) {
                            // only tokens which were names are pushed to stack
                            i += 1;
                        }
                    } else {
                        // rules are always pushed
                        i += 1;
                    }
                }

#if !MICROPY_EMIT_CPYTHON && !MICROPY_ENABLE_DOC_STRING
                // this code discards lonely statements, such as doc strings
                if (input_kind != MP_PARSE_SINGLE_INPUT && rule->rule_id == RULE_expr_stmt && peek_result(&parser, 0) == MP_PARSE_NODE_NULL) {
                    mp_parse_node_t p = peek_result(&parser, 1);
                    if ((MP_PARSE_NODE_IS_LEAF(p) && !MP_PARSE_NODE_IS_ID(p)) || MP_PARSE_NODE_IS_STRUCT_KIND(p, RULE_string)) {
                        pop_result(&parser);
                        pop_result(&parser);
                        push_result_rule(&parser, rule_src_line, rules[RULE_pass_stmt], 0);
                        break;
                    }
                }
#endif

                // always emit these rules, even if they have only 1 argument
                if (rule->rule_id == RULE_expr_stmt || rule->rule_id == RULE_yield_stmt) {
                    emit_rule = true;
                }

                // never emit these rules if they have only 1 argument
                // NOTE: can't put atom_paren here because we need it to distinguisg, for example, [a,b] from [(a,b)]
                // TODO possibly put varargslist_name, varargslist_equal here as well
                if (rule->rule_id == RULE_else_stmt || rule->rule_id == RULE_testlist_comp_3b || rule->rule_id == RULE_import_as_names_paren || rule->rule_id == RULE_typedargslist_name || rule->rule_id == RULE_typedargslist_colon || rule->rule_id == RULE_typedargslist_equal || rule->rule_id == RULE_dictorsetmaker_colon || rule->rule_id == RULE_classdef_2 || rule->rule_id == RULE_with_item_as || rule->rule_id == RULE_assert_stmt_extra || rule->rule_id == RULE_as_name || rule->rule_id == RULE_raise_stmt_from || rule->rule_id == RULE_vfpdef) {
                    emit_rule = false;
                }

                // always emit these rules, and add an extra blank node at the end (to be used by the compiler to store data)
                if (ADD_BLANK_NODE(rule->rule_id)) {
                    emit_rule = true;
                    push_result_node(&parser, MP_PARSE_NODE_NULL);
                    i += 1;
                }

                int num_not_nil = 0;
                for (int x = 0; x < i; ++x) {
                    if (peek_result(&parser, x) != MP_PARSE_NODE_NULL) {
                        num_not_nil += 1;
                    }
                }
                //printf("done and %s n=%d i=%d notnil=%d\n", rule->rule_name, n, i, num_not_nil);
                if (emit_rule) {
                    push_result_rule(&parser, rule_src_line, rule, i);
                } else if (num_not_nil == 0) {
                    push_result_rule(&parser, rule_src_line, rule, i); // needed for, eg, atom_paren, testlist_comp_3b
                    //result_stack_show(parser);
                    //assert(0);
                } else if (num_not_nil == 1) {
                    // single result, leave it on stack
                    mp_parse_node_t pn = MP_PARSE_NODE_NULL;
                    for (int x = 0; x < i; ++x) {
                        mp_parse_node_t pn2 = pop_result(&parser);
                        if (pn2 != MP_PARSE_NODE_NULL) {
                            pn = pn2;
                        }
                    }
                    push_result_node(&parser, pn);
                } else {
                    push_result_rule(&parser, rule_src_line, rule, i);
                }
                break;

            case RULE_ACT_LIST:
                // n=2 is: item item*
                // n=1 is: item (sep item)*
                // n=3 is: item (sep item)* [sep]
                if (backtrack) {
                    list_backtrack:
                    had_trailing_sep = false;
                    if (n == 2) {
                        if (i == 1) {
                            // fail on item, first time round; propagate backtrack
                            goto next_rule;
                        } else {
                            // fail on item, in later rounds; finish with this rule
                            backtrack = false;
                        }
                    } else {
                        if (i == 1) {
                            // fail on item, first time round; propagate backtrack
                            goto next_rule;
                        } else if ((i & 1) == 1) {
                            // fail on item, in later rounds; have eaten tokens so can't backtrack
                            if (n == 3) {
                                // list allows trailing separator; finish parsing list
                                had_trailing_sep = true;
                                backtrack = false;
                            } else {
                                // list doesn't allowing trailing separator; fail
                                goto syntax_error;
                            }
                        } else {
                            // fail on separator; finish parsing list
                            backtrack = false;
                        }
                    }
                } else {
                    for (;;) {
                        uint arg = rule->arg[i & 1 & n];
                        switch (arg & RULE_ARG_KIND_MASK) {
                            case RULE_ARG_TOK:
                                if (mp_lexer_is_kind(lex, arg & RULE_ARG_ARG_MASK)) {
                                    if (i & 1 & n) {
                                        // separators which are tokens are not pushed to result stack
                                    } else {
                                        push_result_token(&parser, lex);
                                    }
                                    mp_lexer_to_next(lex);
                                    // got element of list, so continue parsing list
                                    i += 1;
                                } else {
                                    // couldn't get element of list
                                    i += 1;
                                    backtrack = true;
                                    goto list_backtrack;
                                }
                                break;
                            case RULE_ARG_RULE:
                                push_rule(&parser, rule_src_line, rule, i + 1); // save this list-rule
                                push_rule_from_arg(&parser, arg); // push child of list-rule
                                goto next_rule;
                            default:
                                assert(0);
                        }
                    }
                }
                assert(i >= 1);

                // compute number of elements in list, result in i
                i -= 1;
                if ((n & 1) && (rule->arg[1] & RULE_ARG_KIND_MASK) == RULE_ARG_TOK) {
                    // don't count separators when they are tokens
                    i = (i + 1) / 2;
                }

                if (i == 1) {
                    // list matched single item
                    if (had_trailing_sep) {
                        // if there was a trailing separator, make a list of a single item
                        push_result_rule(&parser, rule_src_line, rule, i);
                    } else {
                        // just leave single item on stack (ie don't wrap in a list)
                    }
                } else {
                    //printf("done list %s %d %d\n", rule->rule_name, n, i);
                    push_result_rule(&parser, rule_src_line, rule, i);
                }
                break;

            default:
                assert(0);
        }
    }

    mp_parse_node_t result;

    // check if we had a memory error
    if (parser.had_memory_error) {
memory_error:
        *parse_error_kind_out = MP_PARSE_ERROR_MEMORY;
        result = MP_PARSE_NODE_NULL;
        goto finished;

    }

    // check we are at the end of the token stream
    if (!mp_lexer_is_kind(lex, MP_TOKEN_END)) {
        goto syntax_error;
    }

    //printf("--------------\n");
    //result_stack_show(parser);
    //printf("rule stack alloc: %d\n", parser.rule_stack_alloc);
    //printf("result stack alloc: %d\n", parser.result_stack_alloc);
    //printf("number of parse nodes allocated: %d\n", num_parse_nodes_allocated);

    // get the root parse node that we created
    assert(parser.result_stack_top == 1);
    result = parser.result_stack[0];

finished:
    // free the memory that we don't need anymore
    m_del(rule_stack_t, parser.rule_stack, parser.rule_stack_alloc);
    m_del(mp_parse_node_t, parser.result_stack, parser.result_stack_alloc);

    // return the result
    return result;

syntax_error:
    if (mp_lexer_is_kind(lex, MP_TOKEN_INDENT)) {
        *parse_error_kind_out = MP_PARSE_ERROR_UNEXPECTED_INDENT;
    } else if (mp_lexer_is_kind(lex, MP_TOKEN_DEDENT_MISMATCH)) {
        *parse_error_kind_out = MP_PARSE_ERROR_UNMATCHED_UNINDENT;
    } else {
        *parse_error_kind_out = MP_PARSE_ERROR_INVALID_SYNTAX;
#ifdef USE_RULE_NAME
        // debugging: print the rule name that failed and the token
        printf("rule: %s\n", rule->rule_name);
#if MICROPY_DEBUG_PRINTERS
        mp_token_show(mp_lexer_cur(lex));
#endif
#endif
    }
    result = MP_PARSE_NODE_NULL;
    goto finished;
}