Parse error when using skip field for lookahead

[bbannier]

I would expect that the skip in the following unit makes no difference to the parsing behavior:

module foo;

public type X = unit {
    xs: uint8[];
    : skip b".";
};

However including it leads to a parse error:

$ printf '\x01\x02\x03.' | spicy-dump foo.spicy
[fatal error] terminating with uncaught exception of type spicy::rt::ParseError: expecting '.' (foo.spicy:5:12)

Dropping the skip makes this parse.

Looking at the generated grammar the only difference seems to be skip introduces an additional indirection,

[debug/grammar] === Grammar foo::X
[debug/grammar]         Epsilon: <epsilon> -> ()
[debug/grammar]            Skip: anon_2 -> skip:       Ctor: anon -> b"." (bytes)
[debug/grammar]  (*)       Unit: foo_X -> xs anon_2
[debug/grammar]        Variable: uintx308 -> uint<8> (container 'xs') [field: xs] [item-type: vector<uint<8>>] [parse-type: vector<uint<8>>]
[debug/grammar]           While: xs  -> while(<look-ahead-found>): uintx308 [field: xs (*)] [item-type: vector<uint<8>>] [parse-type: vector<uint<8>>]
[debug/grammar]       LookAhead: xs_l1 -> {skip:       Ctor: anon -> b"." (bytes) (not a literal)}: <epsilon> | {uint<8> (not a literal)}: xs_l2
[debug/grammar]        Sequence: xs_l2 -> uintx308 xs_l1
[debug/grammar] 
[debug/grammar]   -- Epsilon:
[debug/grammar]      foo_X = false
[debug/grammar]      xs = true
[debug/grammar]      xs_l1 = true
[debug/grammar]      xs_l2 = false
[debug/grammar] 
[debug/grammar]   -- First_1:
[debug/grammar]      foo_X = { anon_2, uintx308 }
[debug/grammar]      xs = { uintx308 }
[debug/grammar]      xs_l1 = { uintx308 }
[debug/grammar]      xs_l2 = { uintx308 }
[debug/grammar] 
[debug/grammar]   -- Follow:
[debug/grammar]      foo_X = {  }
[debug/grammar]      xs = { anon_2 }
[debug/grammar]      xs_l1 = { anon_2 }
[debug/grammar]      xs_l2 = { anon_2 }

vs.

[debug/grammar] === Grammar foo::X
[debug/grammar]         Epsilon: <epsilon> -> ()
[debug/grammar]            Ctor: anon -> b"." (bytes) [field: anon (*)] [item-type: bytes] [parse-type: bytes]
[debug/grammar]  (*)       Unit: foo_X -> xs anon
[debug/grammar]        Variable: uintx308 -> uint<8> (container 'xs') [field: xs] [item-type: vector<uint<8>>] [parse-type: vector<uint<8>>]
[debug/grammar]           While: xs  -> while(<look-ahead-found>): uintx308 [field: xs (*)] [item-type: vector<uint<8>>] [parse-type: vector<uint<8>>]
[debug/grammar]       LookAhead: xs_l1 -> {b"." (bytes) (id 1)}: <epsilon> | {uint<8> (not a literal)}: xs_l2
[debug/grammar]        Sequence: xs_l2 -> uintx308 xs_l1
[debug/grammar] 
[debug/grammar]   -- Epsilon:
[debug/grammar]      foo_X = false
[debug/grammar]      xs = true
[debug/grammar]      xs_l1 = true
[debug/grammar]      xs_l2 = false
[debug/grammar] 
[debug/grammar]   -- First_1:
[debug/grammar]      foo_X = { anon, uintx308 }
[debug/grammar]      xs = { uintx308 }
[debug/grammar]      xs_l1 = { uintx308 }
[debug/grammar]      xs_l2 = { uintx308 }
[debug/grammar] 
[debug/grammar]   -- Follow:
[debug/grammar]      foo_X = {  }
[debug/grammar]      xs = { anon }
[debug/grammar]      xs_l1 = { anon }
[debug/grammar]      xs_l2 = { anon }