#15542: DuplicateRecordFields not honored within a data family? -------------------------------------+------------------------------------- Reporter: michalrus | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I’m observing some weird behavior, which is probably closely related to issue #15149. The following minimized code does not compile on 8.2.1, 8.2.2, but it does compile on 8.4.3. However, in my original (non-free) codebase, this is reversed: 8.2.2 compiles it just fine, and 8.4.3 fails with both errors per usage location at the same time: {{{ src/.../Docs.hs:123:11: error: • Constructor ‘X'Y’ does not have the required strict field(s): z ... src/.../Docs.hs:123:11: error: • Constructor ‘X'Y’ does not have field ‘z’ }}} I noticed, after updating the codebase’s compiler to 8.4.3. If the `z` field is renamed and unique, it compiles correctly. How can I go about debugging/minimizing this? This is the minimized code that works the other way round (OK on 8.4.3, fails on 8.2.2): {{{#!hs {-# LANGUAGE DuplicateRecordFields #-} {-# LANGUAGE KindSignatures #-} {-# LANGUAGE DataKinds #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE StrictData #-} module Main where data AB = A | B class SomeClass (ab :: AB) where data SomeData ab instance SomeClass 'A where data SomeData 'A = SomeData'A{someField :: Int} deriving Show instance SomeClass 'B where data SomeData 'B = SomeData'B{someField :: Int} main :: IO () main = print SomeData'A{someField = 5} }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15542 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler