Support receiving structs as arguments for external functions

[chriseth]

• modify the type system accordingly
• write the decoder for memory
• write the decoder for calldata

[axic]

@chriseth isn't this fully supported via ABIEncoderV2?

[chriseth]

This is still pending, mostly because the stack representation of such types is not yet defined.

[Amxx]

This issue is almost one year old, and is still blocking. It makes it impossible to write interfaces with structs as input. Any idea when we can expect a fix ?

[chriseth]

@Amxx you can use structs if the implementing function is public instead of external:

pragma solidity ^0.5.0;
pragma experimental ABIEncoderV2;

interface I {
    struct S { uint a; uint b; }
    function f(S calldata) external returns (uint);
}

contract C is I {
    function f(I.S memory _s) public returns (uint) {
        return _s.a;
    }
}

[chriseth]

Implemented in #6209