Solidity automatically generated getter function returning tuple instead of struct

Question

// SPDX-License-Identifier: MIT
pragma solidity =0.8.22;

contract A {
    struct User {
        string name;
        uint age;
    }

    mapping(uint => User) public users;

    function getUser(uint id) external view returns (User memory) {
        return users[id];
    }
}

contract B {
    function test() external {
        A a = new A();
        A.User memory user1 = a.getUser(1); // works
        A.User memory user2 = a.users(1); // does not work
    }
}

It seems that the automatically generated getter function users(uint256) is returning tuple(string,uint256) instead of struct User.

I can't find this behavior in the documentation. Is this expected?

Answer 1

Yes this is expected. A default getter function should return values, not a type.

See the docs for a struct example: https://docs.soliditylang.org/en/latest/contracts.html#getter-functions

Answer 2

The Solidity docs mention that some struct values are omitted when a default getter returns the struct, for example, a struct that contains arrays or mappings wouldn't return them.

Meaning this struct:

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.4.0 <0.9.0;

contract Complex {
    struct Data {
        uint a;
        bytes3 b;
        mapping(uint => uint) map;
        uint[3] c;
        uint[] d;
        bytes e;
    }
    mapping(uint => mapping(bool => Data[])) public data;
}

Would return this:

function data(uint arg1, bool arg2, uint arg3)
    public
    returns (uint a, bytes3 b, bytes memory e)
{
    a = data[arg1][arg2][arg3].a;
    b = data[arg1][arg2][arg3].b;
    e = data[arg1][arg2][arg3].e;
}