#16141: StrictData and TypeFamilies regression
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Reporter: RyanGlScott | Owner: (none)
Type: bug | Status: new
Priority: highest | Milestone: 8.8.1
Component: Compiler (Type | Version: 8.6.3
checker) |
Resolution: | Keywords:
Operating System: Unknown/Multiple | Architecture:
Type of failure: GHC rejects | Unknown/Multiple
valid program | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s):
Wiki Page: |
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Comment (by RyanGlScott):
I'm starting to think that this is actually an old bug with `StrictData`,
since the following program (which uses a plain old newtype, not a data
family) also breaks Core Lint in a similar fashion with GHC 8.4.4 or
later:
{{{#!hs
{-# LANGUAGE GADTs #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE StrictData #-}
module Bug where
newtype T a b where
MkT :: forall b a. Int -> T a b
}}}
{{{
$ /opt/ghc/8.4.4/bin/ghc -O -dcore-lint Bug.hs
[1 of 1] Compiling Bug ( Bug.hs, Bug.o )
*** Core Lint errors : in result of Tidy Core ***
<no location info>: warning:
In a case alternative: (I# dt_aXx :: Int#)
Type of case alternatives not the same as the annotation on case:
Actual type: T a_atk b_atj
Annotation on case: T b_atj a_atk
Alt Rhs: dt_aXx
`cast` (Sym (N:T[0]