When I run haskell-language-server in nix-shell in plutus-pioneer-progam i get this error.

whilst processing object file
The symbol was previously defined in
This could be caused by:
   * Loading two different object files which export the same symbol
   * Specifying the same object file twice on the GHCi command line
   * An incorrect `package.conf' entry, causing some object to be
     loaded twice.```
  • Are you on macos?
    – Eugene
    Jan 17, 2022 at 16:31

1 Answer 1


I've found out that the issue comes from the playground stuff. (don't ask me why...)

Commenting the lines [360 .. 365], 24 and 28, the problem goes away. Note that doing this, the old friend GHC Core to PLC plugin; E043:Error comes up, but at least you can navigate the code and look at the documentation.


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