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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/typecheck/should_run/tcrun011.hs
parentebd422aed41048476aa61dd4c520d43becd78682 (diff)
downloadhaskell-16514f272fb42af6e9c7674a9bd6c9dce369231f.tar.gz
Move tests from tests/ghc-regress/* to just tests/*
Diffstat (limited to 'testsuite/tests/typecheck/should_run/tcrun011.hs')
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1 files changed, 25 insertions, 0 deletions
diff --git a/testsuite/tests/typecheck/should_run/tcrun011.hs b/testsuite/tests/typecheck/should_run/tcrun011.hs
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+{-# LANGUAGE ExistentialQuantification, FlexibleContexts,
+ MultiParamTypeClasses #-}
+
+-- !!! Existential data tyes
+-- Hugs didn't like this one
+
+module Main (main) where
+
+
+class MyClass a b where
+ foo :: a -> b -> Int
+
+data Special = forall b. (MyClass Int b)=> MkSpecial b
+data General a = forall b. (MyClass a b)=> MkGeneral b
+
+instance MyClass Int Bool where
+ foo x False = -x
+ foo x True = x
+
+xs :: [General Int]
+xs = [MkGeneral True, MkGeneral False]
+
+main = print [foo (3::Int) x | MkGeneral x <- xs]
+ -- Without the (::Int) part we get an
+ -- incomprehensible error message :-(