Chosing parser based on context

[Snarpix]

I want to parse values, that are have the type in front of them.
Result value of parser - enum:
enum Val {
U8(u8),
U16(u16),
Str(String),
Arr(ValType, Vec),
}

u8 1
[u8] [1, 2, 3, 4]
[str] ["a", "b", "c"]
[u8] [1, "a"] <- Fail
Basically I want to parse the type and then make a decision which parser to use.
According to the docs I should use ignore_with_ctx() method with a custom() parser, but when I call .parse() on InputRef it passes the context(Extra) to the underlying parser, which doesn't know what to do with it.
type_parser().ignore_with_ctx(custom(|r| r.parse(parser_with_type(<extract type from ctx>)))
parser_with_type returns regular parser with Extra = Default.

How can I fix this?