@@ -424,6 +424,9 @@ type family FromExprs a where
424424 FromExprs (t (H DB)) = t (H Result)
425425
426426
427+-- | @Serializable@ witnesses the one-to-one correspondence between the type
428+-- @sql@, which contains SQL expressions, and the type @haskell@, which
429+-- contains the Haskell decoding of rows containing @sql@ SQL expressions.
427430class (ToExprs a exprs, a ~ FromExprs exprs) => Serializable exprs a | exprs -> a
428431instance (ToExprs a exprs, a ~ FromExprs exprs) => Serializable exprs a
429432instance Serializable (Expr Opaque) Opaque