pragma experimental ABIEncoderV2;

contract C {
    struct S { C c; }
    function f(uint a, S[2] memory s1, uint b) public returns (uint r1, C r2, uint r3) {
        r1 = a;
        r2 = s1[0].c;
        r3 = b;
    }
}
// ====
// compileViaYul: also
// ----
// f(uint256,(address)[2],uint256): 7, 0, 0, 8 -> 7, 0, 8