I'm trying to get type definitions for Plutus code in VSCode and I'm getting an unusual error. The first extension in the file is {-# LANGUAGE DataKinds #-} (<- this is a clickable link)

and the error I'm getting is:

Program error: GHC Core to PLC plugin: E043:Error: Reference to a name which is not a local, a builtin, or an external INLINABLE function: Variable PlutusTx.Eq.$fEqMaybe
            No unfolding
Context: Compiling expr: PlutusTx.Eq.$fEqMaybe
Context: Compiling expr: PlutusTx.Eq.$fEqMaybe @ Week01.EnglishAuction.Bid
Context: Compiling expr: PlutusTx.Eq.$fEqMaybe
                           @ Week01.EnglishAuction.Bid
// truncated because of Stackoverflow limits

I've set the language server in VSCode to /nix/store/7bjn84ssy2kdzy7k0izqb3id3bvg6pzb-haskell-language-server-exe-haskell-language-server- and interesting when I run cabal build in my shell I don't get a similar error:

 1:22PM /Users/paymahn/plutus-pioneer-program/code/week01 (nix)  ✘ 130 main ◼
 ❮❮❮ cabal build
Build profile: -w ghc- -O1
In order, the following will be built (use -v for more details):
 - plutus-pioneer-program-week01- (lib) (first run)
Configuring library for plutus-pioneer-program-week01-
Preprocessing library for plutus-pioneer-program-week01-
Building library for plutus-pioneer-program-week01-
[1 of 1] Compiling Week01.EnglishAuction ( src/Week01/EnglishAuction.hs, /Users/paymahn/plutus-pioneer-program/code/week01/dist-newstyle/build/x86_64-osx/ghc-, /Users/paymahn/plutus-pioneer-program/code/week01/dist-newstyle/build/x86_64-osx/ghc- )

1 Answer 1


Here's a diff which shows how to get this fixed in VScode: https://github.com/paymog/plutus-pioneer-program/commit/7a1c2ff206aeaca9496075f18e2989901aeda9fe

Note that even with this, VSCode fails to navigate to type definitions:

enter image description here

  • For me already worked type definition with this error and after I added this switch to ghc options it helped me with other files which include this file to have also type definitions on mouse hover. I used this solution in the other lectures, not in week01.
    – zarej
    Nov 10, 2021 at 6:42

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