#4188: Template Haskell support for reifying non-vanilla data constructors
-------------------------------+--------------------------------------------
Reporter: illissius | Owner: illissius
Type: feature request | Status: closed
Priority: normal | Milestone:
Component: Template Haskell | Version:
Resolution: fixed | Keywords:
Difficulty: | Os: Unknown/Multiple
Testcase: th/T4188 | Architecture: Unknown/Multiple
Failure: None/Unknown |
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Changes (by simonpj):
* status: patch => closed
* testcase: => th/T4188
* resolution: => fixed
Comment:
Very true! Done. As a result I've fixed it so you can reify *anything*
{{{
Wed Jul 21 02:04:37 PDT 2010 [email protected]
* Allow reification of existentials and GADTs
It turns out that TH.Syntax is rich enough to express even GADTs,
provided we express them in equality-predicate form. So for
example
data T a where
MkT1 :: a -> T [a]
MkT2 :: T Int
will appear in TH syntax like this
data T a = forall b. (a ~ [b]) => MkT1 b
| (a ~ Int) => MkT2
While I was at it I also improved the reification of types,
so that we use TH.TupleT and TH.ListT when we can.
M ./compiler/typecheck/TcSplice.lhs -25 +58
}}}
There's a related library patch to tidy up pretty printing
{{{
Wed Jul 21 02:05:38 PDT 2010 [email protected]
* Improve TH pretty printing
M ./Language/Haskell/TH/Ppr.hs -21 +21
}}}
and you need this DPH patch
{{{
Wed Jul 21 08:03:55 PDT 2010 [email protected]
* Take account of ListT and TupleT in TH.Syntax
M ./dph-common/Data/Array/Parallel/Lifted/TH/Repr.hs -1 +4
}}}
I added a test to the regression suite too.
Simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4188#comment:6>
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