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) |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |