#1965: Allow unconstrained existential contexts in newtypes
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Reporter: guest | Owner:
Type: feature request | Status: new
Priority: normal | Milestone: 7.6.1
Component: Compiler | Version: 6.8.1
Resolution: | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: None/Unknown | Difficulty: Unknown
Testcase: | Blockedby:
Blocking: | Related:
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Comment(by simonpj):
Anything involving existentials is going to be hard to implement using
newtype directly. But as 'mokus' says, it might be possible to make a
guarantee, right in the code generator, that certain sorts of data types
do not allocate a box. The conditions are, I think, very nearly as
'mokus' says:
1. Only one constructor
2. Only one field with nonzero width in that constructor (counting
constraints as fields)
3. That field is marked strict
4. That field has a boxed (or polymorphic) type
I think this'd be do-able. The question is how important it is in
practice; it's one more thing to maintain.
Simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1965#comment:9>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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