Synchronizing a vector with a constant value for lookahead

[J-Gras]

I was pulling my hair out when trying to get something like the following to work:

type X = unit {
    a: b"begin-of-X";
    b: bytes &size=10;
};

type Foo = unit {}
    xs: (X &synchronize)[];

    on %synced { confirm; }
};

I just couldn't get the parser to synchronize. Then, @Mohan-Dhawan suggested to use a regex for a. To my surprise that worked! However, given that the above is taken from the docs, requiring a regex feels like a bug.

[bbannier]

Do you have an example input which shows this problem? I tried the following and it seems to work (successful synchronization shown in log, two final vector elements present):

# @TEST-EXEC: spicyc -dj %INPUT -o foo.hlto
# @TEST-EXEC: printf 'begin-of-X1234567890JUNKbegin-of-X1234567890' | HILTI_DEBUG=spicy:spicy-verbose spicy-driver foo.hlto

module foo;

type X = unit {
    a: b"begin-of-X";
    b: bytes &size=10;
};

public type Foo = unit {
    xs: (X &synchronize)[];

    on %synced { confirm; }
};

[bbannier]

Reproducer:

# @TEST-EXEC: spicyc -dj %INPUT -o foo.hlto
# @TEST-EXEC: HILTI_DEBUG=spicy:spicy-verbose spicy-driver foo.hlto -F test.dat

module foo;

type X = unit {
    # a: /A/; # WORKS.
    a: b"A";  # FAILS.
};

# type Foo = unit {
public type Foo = unit {
    %port = 80/tcp;

    xs: (X &synchronize)[];

    on %synced { confirm; }
};

# @TEST-START-FILE test.dat
!spicy-batch v2
@begin-flow id1 stream 80/tcp
@gap id1 1024
@data id1 1
A
@end-flow id1
# @TEST-END-FILE

Verbose logging shows A as lookahead token in the case of regexp parsing, but n/a for the bytes literal.