ast_for_if_stmt(struct compiling *c, const node *n)
{
    /* if_stmt: 'if' test ':' suite ('elif' test ':' suite)*
       ['else' ':' suite]
    */
    char *s;
    int end_lineno, end_col_offset;

    REQ(n, if_stmt);

    if (NCH(n) == 4) {
        expr_ty expression;
        asdl_seq *suite_seq;

        expression = ast_for_expr(c, CHILD(n, 1));
        if (!expression)
            return NULL;
        suite_seq = ast_for_suite(c, CHILD(n, 3));
        if (!suite_seq)
            return NULL;
        get_last_end_pos(suite_seq, &end_lineno, &end_col_offset);

        return If(expression, suite_seq, NULL, LINENO(n), n->n_col_offset,
                  end_lineno, end_col_offset, c->c_arena);
    }

    s = STR(CHILD(n, 4));
    /* s[2], the third character in the string, will be
       's' for el_s_e, or
       'i' for el_i_f
    */
    if (s[2] == 's') {
        expr_ty expression;
        asdl_seq *seq1, *seq2;

        expression = ast_for_expr(c, CHILD(n, 1));
        if (!expression)
            return NULL;
        seq1 = ast_for_suite(c, CHILD(n, 3));
        if (!seq1)
            return NULL;
        seq2 = ast_for_suite(c, CHILD(n, 6));
        if (!seq2)
            return NULL;
        get_last_end_pos(seq2, &end_lineno, &end_col_offset);

        return If(expression, seq1, seq2, LINENO(n), n->n_col_offset,
                  end_lineno, end_col_offset, c->c_arena);
    }
    else if (s[2] == 'i') {
        int i, n_elif, has_else = 0;
        expr_ty expression;
        asdl_seq *suite_seq;
        asdl_seq *orelse = NULL;
        n_elif = NCH(n) - 4;
        /* must reference the child n_elif+1 since 'else' token is third,
           not fourth, child from the end. */
        if (TYPE(CHILD(n, (n_elif + 1))) == NAME
            && STR(CHILD(n, (n_elif + 1)))[2] == 's') {
            has_else = 1;
            n_elif -= 3;
        }
        n_elif /= 4;

        if (has_else) {
            asdl_seq *suite_seq2;

            orelse = _Py_asdl_seq_new(1, c->c_arena);
            if (!orelse)
                return NULL;
            expression = ast_for_expr(c, CHILD(n, NCH(n) - 6));
            if (!expression)
                return NULL;
            suite_seq = ast_for_suite(c, CHILD(n, NCH(n) - 4));
            if (!suite_seq)
                return NULL;
            suite_seq2 = ast_for_suite(c, CHILD(n, NCH(n) - 1));
            if (!suite_seq2)
                return NULL;
            get_last_end_pos(suite_seq2, &end_lineno, &end_col_offset);

            asdl_seq_SET(orelse, 0,
                         If(expression, suite_seq, suite_seq2,
                            LINENO(CHILD(n, NCH(n) - 6)),
                            CHILD(n, NCH(n) - 6)->n_col_offset,
                            end_lineno, end_col_offset, c->c_arena));
            /* the just-created orelse handled the last elif */
            n_elif--;
        }

        for (i = 0; i < n_elif; i++) {
            int off = 5 + (n_elif - i - 1) * 4;
            asdl_seq *newobj = _Py_asdl_seq_new(1, c->c_arena);
            if (!newobj)
                return NULL;
            expression = ast_for_expr(c, CHILD(n, off));
            if (!expression)
                return NULL;
            suite_seq = ast_for_suite(c, CHILD(n, off + 2));
            if (!suite_seq)
                return NULL;

            if (orelse != NULL) {
                get_last_end_pos(orelse, &end_lineno, &end_col_offset);
            } else {
                get_last_end_pos(suite_seq, &end_lineno, &end_col_offset);
            }
            asdl_seq_SET(newobj, 0,
                         If(expression, suite_seq, orelse,
                            LINENO(CHILD(n, off)),
                            CHILD(n, off)->n_col_offset,
                            end_lineno, end_col_offset, c->c_arena));
            orelse = newobj;
        }
        expression = ast_for_expr(c, CHILD(n, 1));
        if (!expression)
            return NULL;
        suite_seq = ast_for_suite(c, CHILD(n, 3));
        if (!suite_seq)
            return NULL;
        get_last_end_pos(orelse, &end_lineno, &end_col_offset);
        return If(expression, suite_seq, orelse,
                  LINENO(n), n->n_col_offset,
                  end_lineno, end_col_offset, c->c_arena);
    }

    PyErr_Format(PyExc_SystemError,
                 "unexpected token in 'if' statement: %s", s);
    return NULL;
}
Unknown