#5366: UNPACK is paranoid about a phantom type argument
---------------------------------+------------------------------------------
Reporter: ekmett | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.0.3 | Keywords:
Testcase: | Blockedby:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: GHC rejects valid program
---------------------------------+------------------------------------------
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'
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5366>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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