Indexed language/parser types

[robrix]

It occurred to me that Language, Parser, etc. could have a (phantom) type parameter for the AST they relate to:

-- in TreeSitter.Language
data Language a

-- in the internal module
foreign import ccall unsafe "vendor/tree-sitter-python/src/parser.c tree_sitter_python" tree_sitter_python :: Ptr (Language a)

-- in the public module
import qualified TreeSitter.Python.AST as AST
import qualified TreeSitter.Python.Internal as Internal

python :: Ptr (Language (AST.Module a))
python = Internal.tree_sitter_python

-- in TreeSitter.Unmarshal
parseByteString :: Unmarshal t => Ptr (TS.Language t) -> ByteString -> IO (Either String t)

This would be a pretty big usability improvement for parseByteString, which otherwise can’t generally infer the type of t.

We might want to index it by the grammar type as well:

python :: Ptr (Language Grammar (AST.Module a))
python = Internal.tree_sitter_python

as that would then allow us to index Tree & Node by the Grammar type, making it much easier to work with their symbols.