module Data.Derive.Arbitrary(makeArbitrary) where
import Data.Derive.DSL.HSE
import Data.List
import Data.Generics.Uniplate.DataOnly
import Data.Derive.DSL.DSL
import Data.Derive.Internal.Derivation
makeArbitrary :: Derivation
makeArbitrary = derivationCustomDSL "Arbitrary" custom $
List [Instance [] "Arbitrary" (List [App "InsDecl" (List [App
"PatBind" (List [App "PVar" (List [App "Ident" (List [String
"arbitrary"])]),App "Nothing" (List []),App "UnGuardedRhs" (List [
App "Do" (List [List [App "Generator" (List [App "PVar" (List [App
"Ident" (List [String "x"])]),App "App" (List [App "Var" (List [
App "UnQual" (List [App "Ident" (List [String "choose"])])]),App
"Tuple" (List [List [App "ExpTypeSig" (List [App "Lit" (List [App
"Int" (List [Int 0])]),App "TyCon" (List [App "UnQual" (List [App
"Ident" (List [String "Int"])])])]),App "InfixApp" (List [App
"App" (List [App "Var" (List [App "UnQual" (List [App "Ident" (
List [String "length"])])]),App "List" (List [MapCtor (App
"RecConstr" (List [App "UnQual" (List [App "Ident" (List [CtorName
])]),List []]))])]),App "QVarOp" (List [App "UnQual" (List [App
"Symbol" (List [String "-"])])]),App "Lit" (List [App "Int" (List
[Int 1])])])]])])]),App "Qualifier" (List [App "Case" (List [App
"Var" (List [App "UnQual" (List [App "Ident" (List [String "x"])])
]),Concat (List [MapCtor (App "Alt" (List [App "PLit" (List [App
"Int" (List [CtorIndex])]),App "UnGuardedAlt" (List [App "Do" (
List [Concat (List [MapField (App "Generator" (List [App "PVar" (
List [App "Ident" (List [Concat (List [String "x",ShowInt
FieldIndex])])]),App "Var" (List [App "UnQual" (List [App "Ident"
(List [String "arbitrary"])])])])),List [App "Qualifier" (List [
App "App" (List [App "Var" (List [App "UnQual" (List [App "Ident"
(List [String "return"])])]),App "Paren" (List [Application (
Concat (List [List [App "Con" (List [App "UnQual" (List [App
"Ident" (List [CtorName])])])],MapField (App "Var" (List [App
"UnQual" (List [App "Ident" (List [Concat (List [String "x",
ShowInt FieldIndex])])])]))]))])])])]])])]),App "BDecls" (List [
List []])])),List [App "Alt" (List [App "PWildCard" (List []),App
"UnGuardedAlt" (List [App "App" (List [App "Var" (List [App
"UnQual" (List [App "Ident" (List [String "error"])])]),App "Lit"
(List [App "String" (List [String
"FATAL ERROR: Arbitrary instance, logic bug"])])])]),App "BDecls"
(List [List []])])]])])])]])]),App "BDecls" (List [List []])])])])
]
custom = customContext context
context :: FullDataDecl -> Context -> Context
context (_,d) _ = nub $ concatMap (f True . fromBangType . snd) $ concatMap ctorDeclFields $ dataDeclCtors d
where
f b (TyVar x) = [ClassA (qname $ b ? "Arbitrary" $ "CoArbitrary") [TyVar x]]
f b (TyFun x y) = f (not b) x ++ f b y
f b x = concatMap (f b) (children x)