Haskell signature highlighting

Currently, the syntax highlighting for Haskell only highlights the first word before `::`.

When I'm writing, I often like to provide a long list of type calculations; for instance, consider below


I believe that it would be better to highlight `f x` and `f . g` also; in general, I think it should highlight up to the preceding parenthesis (i.e. `id` should not be highlighted).

Another strange thing is that if the function before the double colon is `fmap`, no highlighting is applied...


Locate the Haskell syntax-highlighting rules or tokenizer definitions and reproduce the examples from the issue, including signatures using `fmap`. Adjust the highlighting behavior so expressions such as `f x` and `f . g` are covered while `id` before a parenthesis is not, then verify both cases with the project's existing tests.

Written by the indexing model from the issue text.