diff options
Diffstat (limited to 'testsuite/tests/polykinds/T7332.hs')
| -rw-r--r-- | testsuite/tests/polykinds/T7332.hs | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/testsuite/tests/polykinds/T7332.hs b/testsuite/tests/polykinds/T7332.hs index 647dd9333d..79623e9803 100644 --- a/testsuite/tests/polykinds/T7332.hs +++ b/testsuite/tests/polykinds/T7332.hs @@ -18,7 +18,7 @@ instance IsString (DC String) where class Monoid acc => Build acc r where - type BuildR r :: * -- Result type + type BuildR r :: * -- Result type build :: (acc -> BuildR r) -> acc -> r instance Monoid dc => Build dc (DC dx) where @@ -31,9 +31,25 @@ instance (Build dc r, a ~ dc) => Build dc (a->r) where -- The type is inferred -tspan :: (Monoid d, Build (DC d) r, BuildR r ~ DC d) => r +-- tspan :: (Monoid d, Build (DC d) r, BuildR r ~ DC d) => r +tspan :: (Build (DC d) r, BuildR r ~ DC d) => r tspan = build (id :: DC d -> DC d) mempty +{- Wanted: + Build acc0 r0 + Monid acc0 + acc0 ~ DC d0 + DC d0 ~ BuildR r0 +==> + Build (DC d0) r0 + Monoid (DC d0) --> Monoid d0 + DC d- ~ BuildR r0 + +In fact Monoid (DC d0) is a superclass of (Build (DC do) r0) +But during inference we do not take upserclasses of wanteds +-} + + foo = tspan "aa" foo1 = tspan (tspan "aa") |