Include "instance Data a => Lift a" in ForSyDe

[HWoidt]

Issue by HWoidt
Saturday Jul 11, 2015 at 13:04 GMT
Originally opened as https://gits-15.sys.kth.se/ingo/forsyde-deep/issues/16

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Reported by [email protected], Jun 23, 2008

As we know, all the types handled by ForSyDe are required to be instances
of Data.

Creating a "Data a => Lift a" (undecidable) instance would make all
instances of Data (and implicilty all ForSyDe-supported types) also
instances of Lift, sparing us from needing to use $(deriveLift
WhateverDataType).

I created ticket [1] in GHC's track asking for this feature a while ago,
and they accepted to include it in GHC 6.10, but that won't happen in a while.

[1] http://hackage.haskell.org/trac/ghc/ticket/1830

[HWoidt]

Comment by HWoidt
Saturday Jan 23, 2016 at 07:11 GMT

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There has been an update on the GHC ticket. The upcoming version of GHC will support automatic derivation of the Lift instance using "... deriving Lift" through the -XDeriveLift extension.

https://ghc.haskell.org/trac/ghc/ticket/1830
https://phabricator.haskell.org/D1168
https://phabricator.haskell.org/D1269