Repository : ssh://darcs.haskell.org//srv/darcs/testsuite On branch : master
http://hackage.haskell.org/trac/ghc/changeset/4bf1937bac0428ce7955a7fbd8c31b2128b165ab >--------------------------------------------------------------- commit 4bf1937bac0428ce7955a7fbd8c31b2128b165ab Author: Simon Peyton Jones <simo...@microsoft.com> Date: Fri Oct 26 17:28:20 2012 +0100 Test Trac #7354 >--------------------------------------------------------------- tests/indexed-types/should_fail/T7354.hs | 32 ++++++++++++++++++++++++++ tests/indexed-types/should_fail/T7354.stderr | 11 +++++++++ tests/indexed-types/should_fail/all.T | 1 + 3 files changed, 44 insertions(+), 0 deletions(-) diff --git a/tests/indexed-types/should_fail/T7354.hs b/tests/indexed-types/should_fail/T7354.hs new file mode 100644 index 0000000..bdf9e8f --- /dev/null +++ b/tests/indexed-types/should_fail/T7354.hs @@ -0,0 +1,32 @@ +{-# LANGUAGE CPP, TypeFamilies, Rank2Types, FlexibleContexts, FlexibleInstances, GADTs, StandaloneDeriving, UndecidableInstances #-} + +module T7354 where + +type family Base t :: * -> * +data family Prim t :: * -> * + +class Functor (Base t) => Unfoldable t where + embed :: Base t t -> t + ana + :: (a -> Base t a) -- ^ a (Base t)-coalgebra + -> a -- ^ seed + -> t -- ^ resulting fixed point + ana g = a where a = embed . fmap a . g + + +data instance Prim [a] b = Cons a b | Nil deriving (Eq,Ord,Show,Read) + +coalg 0 = Nil +coalg n = Cons n (n-1) +alg Nil = 1 +alg (Cons a b) = a * b + +instance Functor (Prim [a]) where + fmap f (Cons a b) = Cons a (f b) + fmap _ Nil = Nil + +foo = ana alg + +bar = foo -- With 7.6, the definition of foo is simply discarded by + -- by the type checker, which makes Lint complain about bar + diff --git a/tests/indexed-types/should_fail/T7354.stderr b/tests/indexed-types/should_fail/T7354.stderr new file mode 100644 index 0000000..d5c0f1c --- /dev/null +++ b/tests/indexed-types/should_fail/T7354.stderr @@ -0,0 +1,11 @@ + +T7354.hs:28:11: + Occurs check: cannot construct the infinite type: + a ~ Base t (Prim [a] a) + Expected type: Prim [a] a -> Base t (Prim [a] a) + Actual type: Prim [a] a -> a + Relevant bindings include + foo :: Prim [a] a -> t (bound at T7354.hs:28:1) + In the first argument of `ana', namely `alg' + In the expression: ana alg + In an equation for `foo': foo = ana alg diff --git a/tests/indexed-types/should_fail/all.T b/tests/indexed-types/should_fail/all.T index 633f10b..3ab9c5e 100644 --- a/tests/indexed-types/should_fail/all.T +++ b/tests/indexed-types/should_fail/all.T @@ -78,3 +78,4 @@ test('T6123', normal, compile_fail, ['']) test('ExtraTcsUntch', normal, compile_fail, ['']) test('T7010', normal, compile_fail, ['']) test('T7194', normal, compile_fail, ['']) +test('T7354', normal, compile_fail, ['']) _______________________________________________ Cvs-ghc mailing list Cvs-ghc@haskell.org http://www.haskell.org/mailman/listinfo/cvs-ghc
