Add FromField Word

lib/Database/PostgreSQL/Opium/FromField.hs

@@ -56,6 +56,7 @@ instance FromField Char where
   parseField = anyChar
 
 -- | See https://www.postgresql.org/docs/current/datatype-numeric.html.
+-- We assume that 'Int' has 64 bits. This is not guaranteed but reasonable enough.
 instance FromField Int where
   validOid Proxy = Oid.smallint \/ Oid.integer \/ Oid.bigint
   parseField = signed decimal
@@ -65,6 +66,10 @@ instance FromField Integer where
   validOid Proxy = Oid.smallint \/ Oid.integer \/ Oid.bigint
   parseField = signed decimal
 
+instance FromField Word where
+  validOid Proxy = Oid.smallint \/ Oid.integer \/ Oid.bigint
+  parseField = decimal
+
 doubleParser :: Parser Double
 doubleParser = choice
   [ string "NaN" $> nan