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authorDavid Terei <davidterei@gmail.com>2011-07-20 11:09:03 -0700
committerDavid Terei <davidterei@gmail.com>2011-07-20 11:26:35 -0700
commit16514f272fb42af6e9c7674a9bd6c9dce369231f (patch)
treee4f332b45fe65e2a7a2451be5674f887b42bf199 /testsuite/tests/gadt/CasePrune.hs
parentebd422aed41048476aa61dd4c520d43becd78682 (diff)
downloadhaskell-16514f272fb42af6e9c7674a9bd6c9dce369231f.tar.gz
Move tests from tests/ghc-regress/* to just tests/*
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diff --git a/testsuite/tests/gadt/CasePrune.hs b/testsuite/tests/gadt/CasePrune.hs
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+{-# LANGUAGE GADTs, GeneralizedNewtypeDeriving #-}
+
+-- See Trac #1251 and the comments
+-- Note [Pruning dead case alternatives] in types/Unify.lhs
+
+module Main( main ) where
+
+data T a where MkT :: T Int
+
+class C a where ic :: T a
+
+instance C Int where ic = MkT
+
+newtype A = MkA Int deriving( C )
+
+-- axiom CoA : A ~ Int
+-- Hence C Int ~ C A
+
+-- instance C A where
+-- ic :: T A
+-- ic = MkT
+
+icA = ic :: T A -- There are no (non-bot) values of this type
+
+main = print (icA `seq` "ok")
+
+
+