I'm updating @types/atom
https://github.com/icecream17/DefinitelyTyped/blob/master/types/atom

But I'm currently stuck on
https://github.com/atom/atom/blob/master/src/grammar-registry.js#L477

Take the injectionPoint param.

The injectionPoint property on really seems to be used in one file https://github.com/atom/atom/search?q=injectionPoint
https://github.com/atom/atom/blob/10f7d454edb3d61e3c85f6be1c58122b656c295f/src/tree-sitter-grammar.js

The docs say that injectionPoint.language could be called with node__s__. So although it's only called with one node, this property could be typed (...NodeType[]) => string

Unfortunately, I can't figure out what exactly NodeType would represent.
The variables nodes comes from some method in this.tree which comes from this.languageMode.parse

this.languageMode comes from this.buffer.getLanguageMode
this.buffer is a TextBuffer (imported from require(text-buffer))

But this.buffer languageMode.parse doesn't exist???
https://github.com/atom/text-buffer/blob/master/src/text-buffer.js#L2001
https://github.com/atom/text-buffer/search?q=parse

So what could NodeType be???