UNPACK is paranoid about a phantom type argument
Attempting to use code with a phantom type like the following:
newtype Id a = Id Int
inlines fine into
data Foo = Foo {-# UNPACK #-} !(Id Foo) String
but when I go to inline THAT
data Bar = Bar {-# UNPACK #-} !Foo
GHC tells me no, even though the recursive use of Foo is only through a phantom type.
Distilled.hs:3:12:
Warning: Ignoring unusable UNPACK pragma on the
first argument of `Bar'
In the definition of data constructor `Bar'
In the data type declaration for `Bar'
Trac metadata
Trac field | Value |
---|---|
Version | 7.0.3 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |