AbiEncode::encode(complex_solidity_datastruct) return wrong data

[s3cunDa]

Version
ethers v2.0.11

Platform
MacOs

Description
When meet complex struct, like:

struct A {
    address _a;
    uint8 _b;
    uint256 _c;
    bytes _d;
}
struct B {
    A[] AList;
    bytes _e;
}

When using solidity's abi.encode(), it will add a "offset prefix" to indicate the data offset in bytes, example code here:

pragma solidity ^ 0.8.0;

struct A {
    address _a;
    uint8 _b;
    uint256 _c;
    bytes _d;
}
struct B {
    A[] AList;
    bytes _e;
}
contract test{
    function testEncode() public returns (bytes memory result){
        A[] memory AList = new A[](5);
        AList[0] = A({
            _a: address(0),
            _b: 0,
            _c: 0,
            _d: hex"4141414141414141"
        });
        AList[1] = A({
            _a: address(1),
            _b: 0,
            _c: 0,
            _d: hex"4242424242424242"
        });
        AList[2] = A({
            _a: address(2),
            _b: 0,
            _c: 0,
            _d: hex"4343434343434343"
        });
        AList[3] = A({
            _a: address(3),
            _b: 0,
            _c: 0,
            _d: hex"4444444444444444"
        });
        AList[4] = A({
            _a: address(4),
            _b: 0,
            _c: 0,
            _d: hex"4545454545454545"
        });

        B memory BInstance = B({
            AList: AList,
            _e: hex"4646464646464646"
        });
        return abi.encode(BInstance);
    }
}

The corresponding(correct) result is:

0000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000004000000000000000000000000000000000000000000000000000000000000004c0000000000000000000000000000000000000000000000000000000000000000500000000000000000000000000000000000000000000000000000000000000a00000000000000000000000000000000000000000000000000000000000000160000000000000000000000000000000000000000000000000000000000000022000000000000000000000000000000000000000000000000000000000000002e000000000000000000000000000000000000000000000000000000000000003a000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000000009414141414141414141000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000000009424242424242424242000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000000009434343434343434343000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000030000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000000009444444444444444444000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000040000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000000009454545454545454545000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000094646464646464646460000000000000000000000000000000000000000000000

When I tried this code in rust, using the data struct from Abigen:

fn test_encode() {
    let mut a_list: Vec<A> = Vec::new();
    a_list.push(A { 
        _a: "0x0000000000000000000000000000000000000000".parse().unwrap(),
        _b: 0, 
        _c: U256::zero(), 
        _d: "4141414141414141".parse().unwrap()
    });
    a_list.push(A { 
        _a: "0x0000000000000000000000000000000000000001".parse().unwrap(),
        _b: 0, 
        _c: U256::zero(), 
        _d: "4242424242424242".parse().unwrap()
    });
    a_list.push(A { 
        _a: "0x0000000000000000000000000000000000000002".parse().unwrap(),
        _b: 0, 
        _c: U256::zero(), 
        _d: "4343434343434343".parse().unwrap()
    });
    a_list.push(A { 
        _a: "0x0000000000000000000000000000000000000003".parse().unwrap(),
        _b: 0, 
        _c: U256::zero(), 
        _d: "4444444444444444".parse().unwrap()
    });
    a_list.push(A { 
        _a: "0x0000000000000000000000000000000000000004".parse().unwrap(),
        _b: 0, 
        _c: U256::zero(), 
        _d: "4545454545454545".parse().unwrap()
    });
    let b_ins: B = B{
        a_list,
        _e: "4646464646464646".parse().unwrap()
    };
    println!("{:?}", (Bytes::from(AbiEncode::encode(b_ins.clone()))));
}

I got this result:

0x000000000000000000000000000000000000000000000000000000000000004000000000000000000000000000000000000000000000000000000000000004c0000000000000000000000000000000000000000000000000000000000000000500000000000000000000000000000000000000000000000000000000000000a00000000000000000000000000000000000000000000000000000000000000160000000000000000000000000000000000000000000000000000000000000022000000000000000000000000000000000000000000000000000000000000002e000000000000000000000000000000000000000000000000000000000000003a000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000000008414141414141414100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000000008424242424242424200000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000000008434343434343434300000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000030000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000000008444444444444444400000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000040000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000000008454545454545454500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000084646464646464646000000000000000000000000000000000000000000000000

The "offset prefix", in this case is uint256(0x20), is missing somehow.