Description
Your environment
Which OS do you use?
macOS
Which version of GHC do you use and how did you install it?
9.2.2 via Stack project
How is your project built (alternative: link to the project)?
Stack.
The project is available here: https://github.com/kudu-dynamics/blaze
Which LSP client (editor/plugin) do you use?
emacs+lsp-mode
Which version of HLS do you use and how did you install it?
1.8.0.0 from ghcup
Have you configured HLS in any way (especially: a hie.yaml file)?
Yes, see the project link above for details.
What's wrong?
In certain Haskell modules, the hovertip may end up with thousands of lines of entries which reference Core variables (e.g., $dEq). I've created a patch that updates the AtPoint module in HLS to filter out variables by name when they have prefixes that look like Core variables (e.g., "$d" and "$c").
The issue seems to only happens in modules with both typeclass and type definitions. In such a module, when the cursor is on a comment above a type definition which includes a deriving clause, HLS ends up thinking there are thousands of lines to include in the hovertip. The rendering of such a large hovertip buffer can cause emacs to freeze for an extended period of time. In practice, I've noticed ~30 seconds on my several years old MBP.
Should HLS be presenting Core variables to the user through hovertips? Would a patch that removes Core variables be considered for fixing this issue? I ask because I have written such a patch in order to prevent HLS from freezing up emacs. However, I believe there may be a deeper issue: why is an HieAST for a comment associated with thousands of Core variables?
Debug information
A smaller reproducible case is available here: https://github.com/drone-rites/debug-hls
Move the cursor on a comment before one of the data definitions in the Main module and note that there are 126 lines of hover output produced with references to non-unique names of Core variables used in the implementation of type classes (e.g., $dEq_1234 becomes $dEq).
In the blaze-analysis project referenced earlier, the number of lines of hovertip documentation is in the thousands. To reproduce, place the cursor over a comment above any of the type definitions in the Blaze.Types.Pil.Checker module.