accept FnMut instead of just Fn as take_till parameter

[BLucky-gh]

Please complete the following tasks

• I have searched the discussions
• I have searched the open and rejected issues

winnow version

0.6.13

Describe your use case

I was trying to write a parser that runs take_till until it finds a matching bracket (keeping all the brackets found inside balanced), which requires a mutable counter variable to keep track of how many brackets have been found so far

Describe the solution you'd like

Allow passing FnMut to take_till to allow for more complex parsers without needing to make the entire parser stateful or juggling data in and out of a Cell

Alternatives, if applicable

I've used Cell and a move closure to keep the closure Fn while still allowing for mutating the counter, but I feel like it makes the closure unnecessarily complicated and long just to deal with juggling data in and out of the Cell, so I think if there's no functional reason to constraint the parameter to Fn, it should be relaxed

Additional Context

#552 (comment)

[epage]

By take_till, I'm assume you are referring to the impl ContainsToken<T> parameter that is used there and elsewhere.

That affects

• one_of
• none_of
• take_till
• take_while

This is an interesting one as I don't have a good feel for the trade offs of Fn vs FnMut with winnow.

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For related conversations that might spark ideas:

For local context,

• fold's param init func should be FnOnce instead of FnMut  #513

Looking back at nom's issues

• Allow verify to take verification function FnMut? rust-bakery/nom#1636
• Fn / FnMut rust-bakery/nom#1765
• fold's param init func should be FnOnce instead of FnMut rust-bakery/nom#1742