UNPACK should allow recursion that obviously terminates
I want to do this:
{-# LANGUAGE TypeFamilies MagicHash KindSignatures #-}
data Peano = Zero | Succ Peano
data family BigWord (n :: Peano)
data instance BigWord Zero = MachineWord# Word#
data instance BigWord (Succ n) = BigWord {-# UNPACK #-}(BigWord n) {-# UNPACK #-}(BigWord n)
However, the compiler tells me that it is ignoring the UNPACKs, and the only reason I can see is that they are apparently recursive. This exact type of recursion is handled just fine in instance declarations because the recursive instance has fewer type constructors than the head; can't UNPACK do the same thing?
Trac metadata
Trac field | Value |
---|---|
Version | 8.0.2 |
Type | FeatureRequest |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
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Blocking | |
CC | |
Operating system | |
Architecture |