Example source illustrating the problem: <div class="snippet-clipboard-content not

This is caused by <a href="https://gitlab.haskell.org/ghc/ghc/-/wikis/records/overload

A quick bisection shows: <div class="snippet-clipboard-content notranslate positio

Doesn't work if `DuplicateRecordFields` is turned on about barbies-th HOT 5 CLOSED

fumieval commented on June 27, 2024 1

Doesn't work if `DuplicateRecordFields` is turned on

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Comments (5)

gergoerdi commented on June 27, 2024

This is caused by GHC mangling record field names when DuplicateRecordFields is turned on.

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expipiplus1 commented on June 27, 2024

This doesn't seem to work for me (barbies-th-0.1.7).

{-# language TemplateHaskell #-}
{-# language FlexibleInstances #-}
{-# language TypeFamilies #-}
{-# language DuplicateRecordFields #-}

import           Barbies.TH

declareBareB [d|
  data A = A
    { a :: Int
    }  |]

fails with

❯ ghc A.hs
[1 of 1] Compiling A                ( A.hs, A.o, A.dyn_o )

A.hs:10:1: error:
    Illegal variable name: ‘$sel:a:A’
    When splicing a TH declaration:
      instance Barbies.TH.AccessorsB (A_0 Barbies.Internal.Wear.Covered)
    where Barbies.TH.baccessors = A_1 (Barbies.TH.LensB ($sel:a:A_2) (\x_3 b_4 -> b_4{$sel:a:A_2 = x_3}))
   |
10 | declareBareB [d|
   | ^^^^^^^^^^^^^^^^...

Has there been a regression since #4 was merged?

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gergoerdi commented on June 27, 2024

A quick bisection shows:

02ec21b9fa2fb1d09cec8efc8d1db2a5bd7a84ca is the first bad commit
commit 02ec21b9fa2fb1d09cec8efc8d1db2a5bd7a84ca
Author: Fumiaki Kinoshita <[email protected]>
Date:   Wed Jun 3 13:34:56 2020 +0900

    generate lenses

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expipiplus1 commented on June 27, 2024

~~fixing it now~~ Thanks for the quick fix

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Elvecent commented on June 27, 2024

Not sure if related but I get "symbol already defined" errors in Assembler stage when having DuplicateRecordFields on and actual data definitions with duplicate record fields

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