Unit switch with lookahead routing to block not understood by Spicy parser

[bbannier]

I would like to use a unit switch with lookahead and add a block with multiple parsers to a case. This works for unit switch over expressions, but not for lookahead.

type X = unit {
    switch {
        -> { # ERROR: syntax error, unexpected '{', expecting ':'
            : b"a";
            : b"a";
        }
        -> : b"b";
    };
};

To model something like this I would need to move the block to its own unit.

I am marking this Feature Request, but I am pretty sure it is just an unintended limitation in our parser.