pragma abicoder v2;

contract C {
	struct S { uint256 x; }
	struct S2 { uint256 x; uint256 y; }
	function f(S calldata s, S2 calldata s2) public pure returns (uint256 r, uint256 r2) {
		assembly {
			s := s2
			s2 := 4
		}
		r = s.x;
		r2 = s2.x;
	}
}
// ====
// ----
// f((uint256),(uint256,uint256)): 0x42, 0x07, 0x77 -> 0x07, 0x42