Repository : ssh://darcs.haskell.org//srv/darcs/testsuite On branch : master
http://hackage.haskell.org/trac/ghc/changeset/7a7b121393f8bd81008535497bc88d27175e829f >--------------------------------------------------------------- commit 7a7b121393f8bd81008535497bc88d27175e829f Author: Simon Peyton Jones <simo...@microsoft.com> Date: Mon Oct 15 11:07:48 2012 +0100 Test Trac #7332 >--------------------------------------------------------------- tests/indexed-types/should_compile/T7332.hs | 49 +++++++++++++++++++++++++++ tests/indexed-types/should_compile/all.T | 1 + 2 files changed, 50 insertions(+), 0 deletions(-) diff --git a/tests/indexed-types/should_compile/T7332.hs b/tests/indexed-types/should_compile/T7332.hs new file mode 100644 index 0000000..0649741 --- /dev/null +++ b/tests/indexed-types/should_compile/T7332.hs @@ -0,0 +1,49 @@ +{-# LANGUAGE NoMonomorphismRestriction #-} +{-# LANGUAGE MultiParamTypeClasses #-} +{-# LANGUAGE FlexibleInstances, FlexibleContexts #-} +{-# LANGUAGE GeneralizedNewtypeDeriving #-} +{-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE OverloadedStrings #-} +{-# LANGUAGE MagicHash #-} + +module Oleg where + +import GHC.Exts hiding( build ) +import Data.Monoid + +newtype DC d = DC d + deriving (Show, Monoid) + +instance IsString (DC String) where + fromString = DC + + +class Monoid acc => Build acc r where + type BuildR r :: * -- Result type + build :: (acc -> BuildR r) -> acc -> r + +instance Monoid dc => Build dc (DC dx) where + type BuildR (DC dx) = DC dx + build tr acc = tr acc + +instance (Build dc r, a ~ dc) => Build dc (a->r) where + type BuildR (a->r) = BuildR r + build tr acc s = build tr (acc `mappend` s) + + +-- The type is inferred +tspan :: (Monoid d, Build (DC d) r, BuildR r ~ DC d) => r +tspan = build (id :: DC d -> DC d) mempty + +foo = tspan "aa" + +{- Need (Monoid d, Build (DC d) (a -> t), BuildR (a -> t) ~ DC d, IsString a) + +BuildR (a -> t) = BuildR t +Build (DC d) (a -> t) ===> (Build (DC d) t, a ~ DC d) + + -} + +foo1 = tspan (tspan "aa") + +bar = tspan "aa" :: DC String diff --git a/tests/indexed-types/should_compile/all.T b/tests/indexed-types/should_compile/all.T index 067415d..bdb3bff 100644 --- a/tests/indexed-types/should_compile/all.T +++ b/tests/indexed-types/should_compile/all.T @@ -200,5 +200,6 @@ test('T7156', normal, compile, ['']) test('T5591a', normal, compile, ['']) test('T5591b', normal, compile, ['']) test('T7280', normal, compile, ['']) +test('T7332', normal, compile, ['']) _______________________________________________ Cvs-ghc mailing list Cvs-ghc@haskell.org http://www.haskell.org/mailman/listinfo/cvs-ghc
