Description
When DeriveAnyClass is enabled, attempting to "hover" (inspect) a deriving A where A is a class with at least one method will cause HLS to have an internal error.
Your environment
Which OS do you use?
Linux 6.7.0, NixOS, 24.05 (Uakari), 24.05.20240108.317484b
Which version of GHC do you use, and how did you install it?
Version 9.4.8, installed via nixpkgs
How is your project built (alternative: link to the project)?
N/A
Which LSP client (editor/plugin) do you use?
VS Codium+vscode-haskell
Which version of HLS do you use, and how did you install it?
haskell-language-server version: 2.4.0.0 (GHC: 9.4.8), nixpkgs
Have you configured HLS in any way (especially: a hie.yaml file)?
No
Steps to reproduce
{-# LANGUAGE Haskell98 #-}
{-# LANGUAGE DeriveAnyClass #-}
module Main where
class C a where
foo :: a -> Int
newtype Foo = MkFoo Int
deriving Num
newtype Bar a = MkBar a
deriving C
main :: IO ()
main = return ()Expected behaviour
The code above should only result in a missing-methods warning on deriving Num and deriving C
Actual behaviour
Hovering over Num gives you the issue
• No explicit implementation for
‘+’, ‘*’, ‘abs’, ‘signum’, ‘fromInteger’, and (either ‘negate’
And over C
• No explicit implementation for
‘foo’
This is expected, however, when hovering over either HLS also gives an error condition pop-up every time they are hovered:
Error condition, please check your setup and/or the
issue tracker: class: Internal Error: initTcWithGbl failed