Type synonyms can make roles too conservative

import GHC.Exts

type Arr# = Array#

data Foo a = Foo (Arr# a)

type role Foo representational

produces

 error:
    • Role mismatch on variable a:
        Annotation says representational but role nominal is required
    • while checking a role annotation for ‘Foo’

If the type synonym is instead defined

type Arr# a = Array# a

then it works fine.

Trac metadata

Trac field	Value
Version	8.2.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
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