Question about class `implements` and `extends`

[ninthDevilHAUNSTER]

Platform : Ubuntu 20.04
php version : 7.4
php-ast version : 80

I meet a problem about extends and implements attribute in parsing AST_CLASS objects.

Here is the example script

// t.php
<?php

interface b
{
    public function bar();
}

interface c extends b
{
    public function baz();
}

class d implements c
{

    public function bar()
    {
        // TODO: Implement bar() method.
    }

    public function baz()
    {
        // TODO: Implement baz() method.
    }
}

After I parse this script with following script

include 'util.php';
$path = "t.php";
$ast = ast\parse_file($path, $version = 80);
echo ast_dump($ast);

I found something wrong with implements attribute about class c,
I think the child of implements attribute should be null and the extends attribute should be the value of implements attribute.

    1: AST_CLASS
        flags: CLASS_INTERFACE (1)
        name: "c"
        docComment: null
        extends: null
        implements: AST_NAME_LIST // this AST_NAME_LIST should exist in extends attribute ?
            0: AST_NAME
                flags: NAME_NOT_FQ (1)
                name: "b"
        stmts: AST_STMT_LIST
            0: AST_METHOD
                flags: MODIFIER_PUBLIC (1)
                name: "baz"
                docComment: null
                params: AST_PARAM_LIST
                stmts: null
                returnType: null
                attributes: null
                __declId: 2
        attributes: null
        __declId: 3

    2: AST_CLASS
        flags: 0
        name: "d"
        docComment: null
        extends: null
        implements: AST_NAME_LIST
            0: AST_NAME
                flags: NAME_NOT_FQ (1)
                name: "c"
        stmts: AST_STMT_LIST
            0: AST_METHOD
                flags: MODIFIER_PUBLIC (1)
                name: "bar"
                docComment: null
                params: AST_PARAM_LIST
                stmts: AST_STMT_LIST
                returnType: null
                attributes: null
                __declId: 4
            1: AST_METHOD
                flags: MODIFIER_PUBLIC (1)
                name: "baz"
                docComment: null
                params: AST_PARAM_LIST
                stmts: AST_STMT_LIST
                returnType: null
                attributes: null
                __declId: 5
        attributes: null
        __declId: 6

[nikic]

extends for interfaces is equivalent to implements for classes, and PHP represents it internally as such to allow more uniform treatment. The ast extension uses the same internal representation.