Tree-sitter: Support callbacks that return String instead of slice in Rust binding

[ubolonton]

I'm writing a dynamic module for Emacs that exposes tree-sitter functionalities.

A dynamic module in Emacs can only access a buffer's text through String copies (of sub-ranges). It cannot access the internal data structure through &[u8].

Can we add a new parse function to support this use case?

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[ubolonton]

I made a prototype using a new Input trait here.

[maxbrunsfeld]

Hey, sorry for the slow turnaround. I've generalized parse_with and parse_utf16_with to take anything implementing AsRef.

[ubolonton]

Cool, thanks!