solidity/test/libsolidity/syntaxTests/structs/recursion/recursive_struct_forward_reference.sol

pragma experimental ABIEncoderV2;

contract C {
    function f(Data.S memory a) public {}
}
contract Data {
    struct S { S[] x; }
}
// ----
// TypeError: (63-78): Recursive type not allowed for public or external contract functions.