@@ -68,8 +68,7 @@ class BuildHeadersTo hs where
6868instance OVERLAPPING_ BuildHeadersTo '[] where
6969 buildHeadersTo _ = HNil
7070
71−instance OVERLAPPABLE_ ( FromByteString v, BuildHeadersTo xs, KnownSymbol h
72− , Contains h xs ~ 'False)
71+instance OVERLAPPABLE_ ( FromByteString v, BuildHeadersTo xs, KnownSymbol h )
7372 => BuildHeadersTo ((Header h v) ': xs) where
7473 buildHeadersTo headers =
7574 let wantedHeader = CI.mk . pack $ symbolVal (Proxy :: Proxy h)
@@ -89,7 +88,7 @@ class GetHeaders ls where
8988instance OVERLAPPING_ GetHeaders (HList '[]) where
9089 getHeaders _ = []
9190
92−instance OVERLAPPABLE_ ( KnownSymbol h, ToByteString x, GetHeaders (HList xs))
91+instance OVERLAPPABLE_ ( KnownSymbol h, ToByteString x, GetHeaders (HList xs) )
9392 => GetHeaders (HList (Header h x ': xs)) where
9493 getHeaders hdrs = case hdrs of
9594 Header val `HCons` rest -> (headerName , toByteString' val):getHeaders rest
@@ -100,7 +99,7 @@ instance OVERLAPPABLE_ ( KnownSymbol h, ToByteString x, GetHeaders (HList xs))
10099instance OVERLAPPING_ GetHeaders (Headers '[] a) where
101100 getHeaders _ = []
102101
103−instance OVERLAPPABLE_ ( KnownSymbol h, GetHeaders (HList rest), ToByteString v)
102+instance OVERLAPPABLE_ ( KnownSymbol h, GetHeaders (HList rest), ToByteString v )
104103 => GetHeaders (Headers (Header h v ': rest) a) where
105104 getHeaders hs = getHeaders $ getHeadersHList hs
106105
@@ -112,20 +111,15 @@ class AddHeader h v orig new
112111 addHeader :: v -> orig -> new -- ^ N.B.: The same header can't be added multiple times
113112
114113
115−instance OVERLAPPING_ ( KnownSymbol h, ToByteString v, Contains h (fst ': rest) ~ 'False)
114+instance OVERLAPPING_ ( KnownSymbol h, ToByteString v )
116115 => AddHeader h v (Headers (fst ': rest) a) (Headers (Header h v ': fst ': rest) a) where
117116 addHeader a (Headers resp heads) = Headers resp (HCons (Header a) heads)
118117
119118instance OVERLAPPABLE_ ( KnownSymbol h, ToByteString v
120− , new ~ (Headers '[Header h v] a))
119+ , new ~ (Headers '[Header h v] a) )
121120 => AddHeader h v a new where
122121 addHeader a resp = Headers resp (HCons (Header a) HNil)
123122
124−type family Contains x xs where
125− Contains x ((Header x a) ': xs) = 'True
126− Contains x ((Header y a) ': xs) = Contains x xs
127− Contains x '[] = 'False
128−
129123-- $setup
130124-- >>> import Servant.API
131125-- >>> import Data.Aeson