Fail

src/func.rs

@@ -223,10 +223,8 @@ pub trait Monad: Applicative {
     }
 }
 
-/// Equivalent of Haskell's `MonadFail`.
-///
-/// <https://hackage.haskell.org/package/base-4.18.0.0/docs/Control-Monad.html>
-pub trait MonadFail<E>: Monad {
+/// Part of [`MonadFail`] responsible for Haskell's `fail`.
+pub trait Fail<E>: WeakFunctor {
     /// Equivalent of Haskell's `fail`.
     fn fail<'a, A: 'a>(e: E) -> Self::F<'a, A>
     where
@@ -234,6 +232,13 @@ pub trait MonadFail<E>: Monad {
         E: 'a;
 }
 
+/// Equivalent of Haskell's `MonadFail`. Auto-implemented for all [`Fail`]`+`[`Monad`].
+///
+/// <https://hackage.haskell.org/package/base-4.18.0.0/docs/Control-Monad.html>
+pub trait MonadFail<E>: Monad + Fail<E> {}
+
+impl<E, T: Monad + Fail<E>> MonadFail<E> for T {}
+
 /// Equivalent of Haskell's `Alternative`.
 /// Lacks `some`/`many` definitions due to [`FnOnce`] category semantics.
 ///
@@ -296,7 +301,7 @@ pub trait MonadFailAny {
     {
         <Self::W<Result<E1, E0>> as Monad>::bind(Self::map_err(wa, Err), |fa| match fa {
             Ok(a) => <Self::W<Result<E1, E0>> as Pure>::pure(a),
-            Err(e) => <Self::W<Result<E1, E0>> as MonadFail<Result<E1, E0>>>::fail(Ok(e)),
+            Err(e) => <Self::W<Result<E1, E0>> as Fail<Result<E1, E0>>>::fail(Ok(e)),
         })
     }
 }

src/func/classes/composition.rs

@@ -189,7 +189,7 @@ impl<
     }
 }
 
-impl<E, U: Monad, V: MonadFail<E> + LocalFunctor> MonadFail<E> for CompositionClass<U, V> {
+impl<E, U: Monad, V: Fail<E> + LocalFunctor> Fail<E> for CompositionClass<U, V> {
     fn fail<'a, A: 'a>(e: E) -> Self::F<'a, A>
     where
         Self: 'a,

src/func/classes/option.rs

@@ -164,7 +164,7 @@ impl LocalFunctor for OptionClass {
     }
 }
 
-impl MonadFail<()> for OptionClass {
+impl Fail<()> for OptionClass {
     fn fail<'a, A: 'a>(_e: ()) -> Self::F<'a, A>
     where
         Self: 'a,

src/func/classes/result.rs

@@ -188,7 +188,7 @@ impl<E> LocalFunctor for ResultClass<E> {
     }
 }
 
-impl<E> MonadFail<E> for ResultClass<E> {
+impl<E> Fail<E> for ResultClass<E> {
     fn fail<'a, A: 'a>(e: E) -> Self::F<'a, A>
     where
         Self: 'a,

src/func/classes/solo.rs

@@ -145,7 +145,7 @@ impl LocalFunctor for SoloClass {
     }
 }
 
-impl MonadFail<std::convert::Infallible> for SoloClass {
+impl Fail<std::convert::Infallible> for SoloClass {
     fn fail<'a, A: 'a>(e: std::convert::Infallible) -> Self::F<'a, A>
     where
         Self: 'a,

src/func/classes/tryfuture.rs

@@ -182,7 +182,7 @@ impl<E: Clone> SharedFunctor for TryFutureClass<E> {
     }
 }
 
-impl<E> MonadFail<E> for TryFutureClass<E> {
+impl<E> Fail<E> for TryFutureClass<E> {
     fn fail<'a, A: 'a>(e: E) -> Self::F<'a, A>
     where
         Self: 'a,