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  • Glasgow Haskell Compiler
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  • #301

Closed
Open
Created Feb 04, 2005 by wolfram_kahl@trac-wolfram_kahl

GADT constructor constraints ignored

Class constraints on GADT constructore appear to be
ignored.

I tried:

data Expr :: * -> * where
  Const :: Show a => a -> Expr a
  Apply :: Fct a b -> Expr a -> Expr b

and there is no way to define the expected constraint-less
Show instance --- for details, see Expr0.lhs.
Edited Mar 09, 2019 by Simon Marlow
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