Send everything

radn-derive/src/lib.rs

@@ -9,18 +9,18 @@ pub fn derive_shared_functor(input: proc_macro::TokenStream) -> proc_macro::Toke
     let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
     let expanded = quote! {
         impl #impl_generics SharedFunctorAny for #name #ty_generics #where_clause {
-            type SharedAny<'a, A: 'a + Clone> = Self::FAny<'a, A>
+            type SharedAny<'a, A: 'a + Send + Sync + Clone> = Self::FAny<'a, A>
             where
                 Self: 'a;
 
-            fn share<'a, A: 'a + Clone>(fa: Self::FAny<'a, A>) -> Self::SharedAny<'a, A>
+            fn share<'a, A: 'a + Send + Sync + Clone>(fa: Self::FAny<'a, A>) -> Self::SharedAny<'a, A>
             where
                 Self: 'a,
             {
                 fa
             }
 
-            fn unshare<'a, A: 'a + Clone>(sa: Self::SharedAny<'a, A>) -> Self::FAny<'a, A>
+            fn unshare<'a, A: 'a + Send + Sync + Clone>(sa: Self::SharedAny<'a, A>) -> Self::FAny<'a, A>
             where
                 Self: 'a,
             {

src/atomic.rs

@@ -33,7 +33,7 @@ pub trait AtomicBase: 'static + Send + Sync + Clone + Serializable {
     /// Equivalent of [`FactoryBase::ParseError`].
     ///
     /// [`FactoryBase::ParseError`]: crate::rcore::FactoryBase::ParseError
-    type AParseError: Error;
+    type AParseError: Error + Send;
 }
 
 /// This trait combines functionality of [`Mentionable`] and [`Factory`],

src/flow/binary.rs

@@ -18,10 +18,10 @@ pub type KeySplit<'a, BT> = (<BT as BinaryTrees<'a>>::Tree, <BT as BinaryTrees<'
 pub type BTWrap<'a, BT, A> = WrapC<'a, A, BT>;
 
 pub trait BinaryTrees<'a>: FunctorContext<'a, T = Self::_Tm> + Clone {
-    type Node: 'a;
-    type Reference: 'a;
-    type Tree: 'a;
-    type Key: 'a + Clone;
+    type Node: 'a + Send;
+    type Reference: 'a + Send;
+    type Tree: 'a + Send;
+    type Key: 'a + Send + Clone;
     type Comparator: Comparator<Self::Key>;
 
     type _Tm: Monad<'a>;
@@ -153,7 +153,7 @@ impl Display for HeightError {
 
 pub trait BinaryTreesHeight<'a>: BinaryTrees<'a> {
     fn height(&self, tree: &Self::Tree) -> u64;
-    fn height_error<T: 'a>(&self, error: HeightError) -> BTWrap<'a, Self, T>;
+    fn height_error<T: 'a + Send>(&self, error: HeightError) -> BTWrap<'a, Self, T>;
 }
 
 pub trait BinaryTreesTryJoin<'a>: BinaryTrees<'a> {

src/flow/binary/avl.rs

@@ -50,10 +50,10 @@ pub trait BinaryTreesAvl<'a>:
         }
     }
 
-    fn assume_bind<T>(
+    fn assume_bind<T: Send>(
         self,
         tree: &Self::Tree,
-        f: impl 'a + FnOnce(Self, Self::Tree, Self::Key, Self::Tree) -> BTWrap<'a, Self, T>,
+        f: impl 'a + Send + FnOnce(Self, Self::Tree, Self::Key, Self::Tree) -> BTWrap<'a, Self, T>,
     ) -> BTWrap<'a, Self, T> {
         Self::bind(self.assume_node(tree), move |node| {
             let (tl, tr, key) = self.split(&node);

src/flow/binary/balancing.rs

@@ -5,9 +5,9 @@ use super::{avl::*, bound::*, *};
 pub trait BinaryTreesUnbalanced<'a>: BinaryTreesHeight<'a> {
     fn tree_of_with_height(&self, node: Self::Node, height: u64) -> BTWrap<'a, Self, Self::Tree>;
 
-    fn balancing_error<T: 'a>(&self, error: BalancingError) -> BTWrap<'a, Self, T>;
+    fn balancing_error<T: 'a + Send>(&self, error: BalancingError) -> BTWrap<'a, Self, T>;
 
-    fn balancing_bind<A: 'a, B: 'a>(
+    fn balancing_bind<A: 'a, B: 'a + Send>(
         &self,
         ra: Result<A, BalancingError>,
         f: impl FnOnce(A) -> BTWrap<'a, Self, B>,
@@ -153,7 +153,7 @@ impl<'a, BT: BinaryTreesUnbalanced<'a>> BinaryTreesHeight<'a> for BalancedTrees<
         self.0.height(tree)
     }
 
-    fn height_error<T: 'a>(&self, error: HeightError) -> BTWrap<'a, Self, T> {
+    fn height_error<T: 'a + Send>(&self, error: HeightError) -> BTWrap<'a, Self, T> {
         self.0.height_error(error)
     }
 }
@@ -176,7 +176,10 @@ impl<'a, BT: BinaryTreesUnbalanced<'a> + BinaryTreesTryJoin<'a>> BinaryTreesTryJ
 impl<'a, BT: BinaryTreesUnbalanced<'a> + BinaryTreesBindable<'a>> BinaryTreesBindable<'a>
     for BalancedTrees<BT>
 {
-    fn bounds_error<T: 'a>(&self, error: bounds::BoundsError<Self::Key>) -> BTWrap<'a, Self, T> {
+    fn bounds_error<T: 'a + Send>(
+        &self,
+        error: bounds::BoundsError<Self::Key>,
+    ) -> BTWrap<'a, Self, T> {
         self.0.bounds_error(error)
     }
 }

src/flow/binary/bound.rs

@@ -38,9 +38,9 @@ impl<'a, BT: FunctorContext<'a>> FunctorContext<'a> for BoundTrees<BT> {
 }
 
 pub trait BinaryTreesBindable<'a>: BinaryTrees<'a> {
-    fn bounds_error<T: 'a>(&self, error: BoundsError<Self::Key>) -> BTWrap<'a, Self, T>;
+    fn bounds_error<T: 'a + Send>(&self, error: BoundsError<Self::Key>) -> BTWrap<'a, Self, T>;
 
-    fn bounds_bind<A: 'a, B: 'a>(
+    fn bounds_bind<A: 'a + Send, B: 'a + Send>(
         &self,
         ra: Result<A, BoundsError<Self::Key>>,
         f: impl FnOnce(A) -> BTWrap<'a, Self, B>,
@@ -169,7 +169,7 @@ impl<'a, BT: BinaryTreesBindable<'a> + BinaryTreesHeight<'a>> BinaryTreesHeight<
         self.0.height(&tree.bound)
     }
 
-    fn height_error<T: 'a>(&self, error: HeightError) -> BTWrap<'a, Self, T> {
+    fn height_error<T: 'a + Send>(&self, error: HeightError) -> BTWrap<'a, Self, T> {
         self.0.height_error(error)
     }
 }

src/flow/comparator.rs

@@ -15,7 +15,7 @@ pub enum Comparison {
 /// assert_eq!(DefaultComparator.compare(&2, &2), Comparison::E);
 /// assert_eq!(DefaultComparator.compare(&3, &1), Comparison::R);
 /// ```
-pub trait Comparator<A> {
+pub trait Comparator<A>: Send + Sync {
     fn compare(&self, kl: &A, kr: &A) -> Comparison;
 
     fn equal(&self, kl: &A, kr: &A) -> bool {
@@ -40,10 +40,10 @@ pub struct RcComparator<C>(C);
 
 mod rc_comparator_impl {
     use super::*;
-    use std::rc::Rc;
+    use std::sync::Arc;
 
-    impl<A, C: Comparator<A>> Comparator<Rc<A>> for RcComparator<C> {
-        fn compare(&self, kl: &Rc<A>, kr: &Rc<A>) -> Comparison {
+    impl<A, C: Comparator<A>> Comparator<Arc<A>> for RcComparator<C> {
+        fn compare(&self, kl: &Arc<A>, kr: &Arc<A>) -> Comparison {
             self.0.compare(kl, kr)
         }
     }

src/flow/speculative.rs

@@ -6,14 +6,14 @@ type Frwa<'a, A, E0, E1, Fallible> =
 type Wwa<'a, A, E0, E1, Fallible> = WrapE<'a, WrapE<'a, A, E0, Fallible>, E1, Fallible>;
 
 trait SpeculativeFailImpl<'a>: MonadFailAny<'a> {
-    fn _speculative_a_wb<A: 'a, B: 'a, E0: 'a, E1: 'a>(
+    fn _speculative_a_wb<A: 'a + Send, B: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         a: A,
         wb: WrapE<'a, B, E0, Self>,
     ) -> WrapE<'a, (A, B), Result<E0, E1>, Self> {
         Self::map_err(<Self::W<E0> as Functor>::fmap(wb, |b| (a, b)), Ok)
     }
 
-    fn _speculative_ra_wb<A: 'a, B: 'a, E0: 'a, E1: 'a>(
+    fn _speculative_ra_wb<A: 'a + Send, B: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         ra: Result<A, E0>,
         wb: WrapE<'a, B, E0, Self>,
     ) -> WrapE<'a, (A, B), Result<E0, E1>, Self> {
@@ -23,7 +23,7 @@ trait SpeculativeFailImpl<'a>: MonadFailAny<'a> {
         }
     }
 
-    fn _speculative_ra_rwb<A: 'a, B: 'a, E0: 'a, E1: 'a>(
+    fn _speculative_ra_rwb<A: 'a + Send, B: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         ra: Result<A, E0>,
         rwb: Result<WrapE<'a, B, E0, Self>, E1>,
     ) -> WrapE<'a, (A, B), Result<E0, E1>, Self> {
@@ -33,7 +33,7 @@ trait SpeculativeFailImpl<'a>: MonadFailAny<'a> {
         }
     }
 
-    fn _speculative_ra_frwb<A: 'a, B: 'a, E0: 'a, E1: 'a>(
+    fn _speculative_ra_frwb<A: 'a + Send, B: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         ra: Result<A, E0>,
         frwb: Frwa<'a, B, E0, E1, Self>,
     ) -> WrapE<'a, (A, B), Result<E0, E1>, Self> {
@@ -42,14 +42,14 @@ trait SpeculativeFailImpl<'a>: MonadFailAny<'a> {
         }))
     }
 
-    fn _speculative_fra_wb<A: 'a, B: 'a, E0: 'a>(
+    fn _speculative_fra_wb<A: 'a + Send, B: 'a + Send, E0: 'a + Send>(
         fra: Wrap<'a, Result<A, E0>, Self::T>,
         wb: WrapE<'a, B, E0, Self>,
     ) -> WrapE<'a, (A, B), E0, Self> {
         <Self::W<E0> as ApplicativeTuple>::tuple((Self::stuff(fra), wb))
     }
 
-    fn _speculative_wa_frwb<A: 'a, B: 'a, E0: 'a, E1: 'a>(
+    fn _speculative_wa_frwb<A: 'a + Send, B: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, A, E0, Self>,
         frwb: Frwa<'a, B, E0, E1, Self>,
     ) -> WrapE<'a, (A, B), Result<E0, E1>, Self> {
@@ -67,7 +67,7 @@ trait SpeculativeFailImpl<'a>: MonadFailAny<'a> {
         ))
     }
 
-    fn _speculative_frwa_wb<A: 'a, B: 'a, E0: 'a, E1: 'a>(
+    fn _speculative_frwa_wb<A: 'a + Send, B: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         frwa: Frwa<'a, A, E0, E1, Self>,
         wb: WrapE<'a, B, E0, Self>,
     ) -> WrapE<'a, (A, B), Result<E0, E1>, Self> {
@@ -77,7 +77,7 @@ trait SpeculativeFailImpl<'a>: MonadFailAny<'a> {
         )
     }
 
-    fn _speculative<A: 'a, B: 'a, E0: 'a, E1: 'a>(
+    fn _speculative<A: 'a + Send, B: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wwa: Wwa<'a, A, E0, E1, Self>,
         wwb: Wwa<'a, B, E0, E1, Self>,
     ) -> WrapE<'a, (A, B), Result<E0, E1>, Self> {
@@ -98,7 +98,7 @@ trait SpeculativeFailImpl<'a>: MonadFailAny<'a> {
 }
 
 pub trait SpeculativeFail<'a>: MonadFailAny<'a> {
-    fn speculative<A: 'a, B: 'a, E0: 'a, E1: 'a>(
+    fn speculative<A: 'a + Send, B: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wwa: Wwa<'a, A, E0, E1, Self>,
         wwb: Wwa<'a, B, E0, E1, Self>,
     ) -> WrapE<'a, (A, B), Result<E0, E1>, Self> {

src/flow/traversible.rs

@@ -2,30 +2,36 @@
 
 pub mod algorithms;
 
-use std::rc::Rc;
+use std::sync::Arc;
 
 use crate::flow::comparator::*;
 use crate::func::*;
 
 pub type Split<'a, T, A, D> = (
-    Rc<dyn TraversibleBinaryTree<'a, T, A, D>>,
-    Rc<dyn TraversibleBinaryTree<'a, T, A, D>>,
+    Arc<dyn TraversibleBinaryTree<'a, T, A, D>>,
+    Arc<dyn TraversibleBinaryTree<'a, T, A, D>>,
     A,
 );
 
-pub trait TraversibleBinaryNode<'a, T: Monad<'a>, A: 'a, D: 'a + PartialEq>: 'a {
+pub trait TraversibleBinaryNode<'a, T: Monad<'a>, A: 'a, D: 'a + PartialEq>:
+    'a + Send + Sync
+{
     fn split(&self) -> Split<'a, T, A, D>;
 
-    fn to_tree(self: Rc<Self>) -> Rc<dyn TraversibleBinaryTree<'a, T, A, D>>;
+    fn to_tree(self: Arc<Self>) -> Arc<dyn TraversibleBinaryTree<'a, T, A, D>>;
 }
 
-pub trait TraversibleBinaryReference<'a, T: Monad<'a>, A: 'a, D: 'a + PartialEq>: 'a {
-    fn resolve(&self) -> Wrap<'a, Rc<dyn TraversibleBinaryNode<'a, T, A, D>>, T>;
+pub trait TraversibleBinaryReference<'a, T: Monad<'a>, A: 'a, D: 'a + PartialEq>:
+    'a + Send + Sync
+{
+    fn resolve(&self) -> Wrap<'a, Arc<dyn TraversibleBinaryNode<'a, T, A, D>>, T>;
 
     /// This should be enough to compare reference for equality.
     fn data(&self) -> D;
 }
 
-pub trait TraversibleBinaryTree<'a, T: Monad<'a>, A: 'a, D: 'a + PartialEq>: 'a {
-    fn refer(&self) -> Option<Rc<dyn TraversibleBinaryReference<'a, T, A, D>>>;
+pub trait TraversibleBinaryTree<'a, T: Monad<'a>, A: 'a, D: 'a + PartialEq>:
+    'a + Send + Sync
+{
+    fn refer(&self) -> Option<Arc<dyn TraversibleBinaryReference<'a, T, A, D>>>;
 }

src/flow/traversible/algorithms/contains.rs

@@ -1,8 +1,8 @@
 use crate::{flow::traversible::*, func::class_prelude::MonadFail};
 
-pub fn n_contains<'a, T: MonadFail<'a, ()>, A: 'a + Clone, D: 'a + PartialEq>(
+pub fn n_contains<'a, T: MonadFail<'a, ()>, A: 'a + Send + Clone, D: 'a + PartialEq>(
     comparator: &'a dyn Comparator<A>,
-    n_set: Rc<dyn TraversibleBinaryNode<'a, T, A, D>>,
+    n_set: Arc<dyn TraversibleBinaryNode<'a, T, A, D>>,
     key: A,
 ) -> T::F<()> {
     let (t_setl, t_setr, k_set) = n_set.split();
@@ -13,17 +13,17 @@ pub fn n_contains<'a, T: MonadFail<'a, ()>, A: 'a + Clone, D: 'a + PartialEq>(
     }
 }
 
-pub fn r_contains<'a, T: MonadFail<'a, ()>, A: 'a + Clone, D: 'a + PartialEq>(
+pub fn r_contains<'a, T: MonadFail<'a, ()>, A: 'a + Send + Clone, D: 'a + PartialEq>(
     comparator: &'a dyn Comparator<A>,
-    r_set: Rc<dyn TraversibleBinaryReference<'a, T, A, D>>,
+    r_set: Arc<dyn TraversibleBinaryReference<'a, T, A, D>>,
     key: A,
 ) -> T::F<()> {
     T::bind(r_set.resolve(), |n_set| n_contains(comparator, n_set, key))
 }
 
-pub fn t_contains<'a, T: MonadFail<'a, ()>, A: 'a + Clone, D: 'a + PartialEq>(
+pub fn t_contains<'a, T: MonadFail<'a, ()>, A: 'a + Send + Clone, D: 'a + PartialEq>(
     comparator: &'a dyn Comparator<A>,
-    t_set: Rc<dyn TraversibleBinaryTree<'a, T, A, D>>,
+    t_set: Arc<dyn TraversibleBinaryTree<'a, T, A, D>>,
     key: A,
 ) -> T::F<()> {
     match t_set.refer() {

src/flow/traversible/algorithms/subset.rs

@@ -6,16 +6,18 @@ fn and(_l: (), _r: ()) {}
 
 struct SubsetContext<'a, T: MonadFail<'a, ()>, A: 'a, D: 'a + PartialEq> {
     comparator: &'a dyn Comparator<A>,
-    n_subset: Rc<dyn TraversibleBinaryNode<'a, T, A, D>>,
-    n_superset: Rc<dyn TraversibleBinaryNode<'a, T, A, D>>,
+    n_subset: Arc<dyn TraversibleBinaryNode<'a, T, A, D>>,
+    n_superset: Arc<dyn TraversibleBinaryNode<'a, T, A, D>>,
     k_l: Option<A>,
     k_r: Option<A>,
-    t_superl: Rc<dyn TraversibleBinaryTree<'a, T, A, D>>,
-    t_superr: Rc<dyn TraversibleBinaryTree<'a, T, A, D>>,
+    t_superl: Arc<dyn TraversibleBinaryTree<'a, T, A, D>>,
+    t_superr: Arc<dyn TraversibleBinaryTree<'a, T, A, D>>,
     k_super: A,
 }
 
-impl<'a, T: 'a + MonadFail<'a, ()>, A: 'a + Clone, D: 'a + PartialEq> SubsetContext<'a, T, A, D> {
+impl<'a, T: 'a + MonadFail<'a, ()>, A: 'a + Send + Clone, D: 'a + PartialEq>
+    SubsetContext<'a, T, A, D>
+{
     fn on_l(self, (t_subl, t_subr, k_sub): Split<'a, T, A, D>) -> T::F<()> {
         T::la2(
             algorithms::contains::t_contains(self.comparator, self.t_superl.clone(), k_sub.clone()),
@@ -148,10 +150,10 @@ fn outside_r<A>(comparator: &dyn Comparator<A>, k_r: &Option<A>, k_super: &A) ->
     }
 }
 
-pub fn n_subset_of_n<'a, T: MonadFail<'a, ()>, A: 'a + Clone, D: 'a + PartialEq>(
+pub fn n_subset_of_n<'a, T: MonadFail<'a, ()>, A: 'a + Send + Clone, D: 'a + PartialEq>(
     comparator: &'a dyn Comparator<A>,
-    n_subset: Rc<dyn TraversibleBinaryNode<'a, T, A, D>>,
-    n_superset: Rc<dyn TraversibleBinaryNode<'a, T, A, D>>,
+    n_subset: Arc<dyn TraversibleBinaryNode<'a, T, A, D>>,
+    n_superset: Arc<dyn TraversibleBinaryNode<'a, T, A, D>>,
     k_l: Option<A>,
     k_r: Option<A>,
 ) -> T::F<()> {
@@ -169,10 +171,15 @@ pub fn n_subset_of_n<'a, T: MonadFail<'a, ()>, A: 'a + Clone, D: 'a + PartialEq>
     .test_optimised()
 }
 
-pub fn r_subset_of_r_unoptimised<'a, T: MonadFail<'a, ()>, A: 'a + Clone, D: 'a + PartialEq>(
+pub fn r_subset_of_r_unoptimised<
+    'a,
+    T: MonadFail<'a, ()>,
+    A: 'a + Send + Clone,
+    D: 'a + PartialEq,
+>(
     comparator: &'a dyn Comparator<A>,
-    r_subset: Rc<dyn TraversibleBinaryReference<'a, T, A, D>>,
-    r_superset: Rc<dyn TraversibleBinaryReference<'a, T, A, D>>,
+    r_subset: Arc<dyn TraversibleBinaryReference<'a, T, A, D>>,
+    r_superset: Arc<dyn TraversibleBinaryReference<'a, T, A, D>>,
     k_l: Option<A>,
     k_r: Option<A>,
 ) -> T::F<()> {
@@ -183,9 +190,9 @@ pub fn r_subset_of_r_unoptimised<'a, T: MonadFail<'a, ()>, A: 'a + Clone, D: 'a
     )
 }
 
-fn r_subset_of_r_optimised<'a, T: MonadFail<'a, ()>, A: 'a + Clone, D: 'a + PartialEq>(
-    r_subset: Rc<dyn TraversibleBinaryReference<'a, T, A, D>>,
-    r_superset: Rc<dyn TraversibleBinaryReference<'a, T, A, D>>,
+fn r_subset_of_r_optimised<'a, T: MonadFail<'a, ()>, A: 'a + Send + Clone, D: 'a + PartialEq>(
+    r_subset: Arc<dyn TraversibleBinaryReference<'a, T, A, D>>,
+    r_superset: Arc<dyn TraversibleBinaryReference<'a, T, A, D>>,
     comparator: &'a dyn Comparator<A>,
     k_l: Option<A>,
     k_r: Option<A>,
@@ -197,10 +204,10 @@ fn r_subset_of_r_optimised<'a, T: MonadFail<'a, ()>, A: 'a + Clone, D: 'a + Part
     }
 }
 
-pub fn t_subset_of_t<'a, T: MonadFail<'a, ()>, A: 'a + Clone, D: 'a + PartialEq>(
+pub fn t_subset_of_t<'a, T: MonadFail<'a, ()>, A: 'a + Send + Clone, D: 'a + PartialEq>(
     comparator: &'a dyn Comparator<A>,
-    t_subset: Rc<dyn TraversibleBinaryTree<'a, T, A, D>>,
-    t_superset: Rc<dyn TraversibleBinaryTree<'a, T, A, D>>,
+    t_subset: Arc<dyn TraversibleBinaryTree<'a, T, A, D>>,
+    t_superset: Arc<dyn TraversibleBinaryTree<'a, T, A, D>>,
     k_l: Option<A>,
     k_r: Option<A>,
 ) -> T::F<()> {

src/func.rs

@@ -30,8 +30,8 @@ pub use self::extensions::MonadExt;
 /// Part of Haskell's `Functor f` responsible for having `f a`.
 ///
 /// <https://hackage.haskell.org/package/base-4.18.0.0/docs/Data-Functor.html>
-pub trait WeakFunctor<'a>: 'a {
-    type F<A: 'a>: 'a;
+pub trait WeakFunctor<'a>: 'a + Send {
+    type F<A: 'a + Send>: 'a + Send;
 }
 
 pub type Wrap<'a, A, T> = <T as WeakFunctor<'a>>::F<A>;
@@ -43,15 +43,18 @@ pub trait Functor<'a>: WeakFunctor<'a> {
     /// Equivalent or Haskell's `fmap`.
     /// Due to Rust limitations, it's not a `function->function` conversion.
     /// For that see [`derivations::fmap`].
-    fn fmap<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> B) -> Self::F<B>;
+    fn fmap<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + Send + FnOnce(A) -> B,
+    ) -> Self::F<B>;
 
     /// Equivalent of Haskell's `$>`/`<$`.
-    fn replace<A: 'a, B: 'a>(fa: Self::F<A>, b: B) -> Self::F<B> {
+    fn replace<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, b: B) -> Self::F<B> {
         Self::fmap(fa, |_| b)
     }
 
     /// Equivalent of Haskell's `void`.
-    fn void<A: 'a>(fa: Self::F<A>) -> Self::F<()> {
+    fn void<A: 'a + Send>(fa: Self::F<A>) -> Self::F<()> {
         Self::replace(fa, ())
     }
 }
@@ -59,29 +62,32 @@ pub trait Functor<'a>: WeakFunctor<'a> {
 /// Part of [`Applicative`] responsible for Haskell's value lifting, `pure`.
 pub trait Pure<'a>: Functor<'a> {
     /// Equivalent of Haskell's `pure`/`return`.
-    fn pure<A: 'a>(a: A) -> Self::F<A>;
+    fn pure<A: 'a + Send>(a: A) -> Self::F<A>;
 }
 
 /// Part of [`Applicative`] responsible for Haskell's sequential application `<*>`.
 pub trait ApplicativeSeq<'a>: Functor<'a> {
     /// Equivalent of Haskell's `<*>`.
-    fn seq<A: 'a, B: 'a>(ff: Self::F<impl 'a + FnOnce(A) -> B>, fa: Self::F<A>) -> Self::F<B>;
+    fn seq<A: 'a + Send, B: 'a + Send>(
+        ff: Self::F<impl 'a + Send + FnOnce(A) -> B>,
+        fa: Self::F<A>,
+    ) -> Self::F<B>;
 }
 
 /// Part of [`Applicative`] responsible for Haskell's result combination `listA2`.
 pub trait ApplicativeLA2<'a>: Functor<'a> {
     /// Equivalent of Haskell's `listA2`.
-    fn la2<A: 'a, B: 'a, C: 'a>(
+    fn la2<A: 'a + Send, B: 'a + Send, C: 'a + Send>(
         fa: Self::F<A>,
         fb: Self::F<B>,
-        f: impl 'a + FnOnce(A, B) -> C,
+        f: impl 'a + Send + FnOnce(A, B) -> C,
     ) -> Self::F<C>;
 }
 
 /// Part of [`Applicative`] responsible for Rust-style result combination, specifically for tuples.
 pub trait ApplicativeTuple<'a>: Functor<'a> {
     /// Similar to Haskell's `listA2` but with [Iterator::collect]-ish semantics.
-    fn tuple<A: 'a, B: 'a>(fab: (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)>;
+    fn tuple<A: 'a + Send, B: 'a + Send>(fab: (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)>;
 }
 
 /// Equivalent of Haskell's `Applicative`.
@@ -92,12 +98,12 @@ pub trait Applicative<'a>:
     Pure<'a> + ApplicativeSeq<'a> + ApplicativeLA2<'a> + ApplicativeTuple<'a> + ApplicativeSelect<'a>
 {
     /// Equivalent of Haskell's `*>`/`>>`.
-    fn discard_first<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
+    fn discard_first<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
         Self::seq(Self::replace(fa, |b| b), fb)
     }
 
     /// Equivalent of Haskell's `<*`.
-    fn discard_second<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
+    fn discard_second<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
         Self::la2(fa, fb, |a, _| a)
     }
 }
@@ -109,7 +115,10 @@ pub trait Monad<'a>: Applicative<'a> {
     /// Equivalent of Haskell's `>==`.
     /// Due to Rust limitations, it's not a `function->function` conversion.
     /// For that see [`derivations::bind`].
-    fn bind<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> Self::F<B>) -> Self::F<B>;
+    fn bind<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + Send + FnOnce(A) -> Self::F<B>,
+    ) -> Self::F<B>;
 
     /// Included for optimisation and clarity.
     /// Generally, [`Monad::bind`] should be enough implement it.
@@ -117,10 +126,10 @@ pub trait Monad<'a>: Applicative<'a> {
     /// On practice, you generally shouldn't be using [`Monad::bind`]/[`Pure::pure`]/[`Functor::fmap`] here.
     ///
     /// [`StacklessInstance::iterate`]: instances::stackless::StacklessInstance::iterate
-    fn iterate<B: 'a>(f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B>;
+    fn iterate<B: 'a + Send>(f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B>;
 
     /// Equivalent of Haskell's `join`.
-    fn join<A: 'a>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
+    fn join<A: 'a + Send>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
         Self::bind(ffa, |fa| fa)
     }
 }

src/func/applicative_select.rs

@@ -1,6 +1,6 @@
 use super::*;
 
-pub enum Selected<'a, A: 'a, B: 'a, T: ?Sized + WeakFunctor<'a>> {
+pub enum Selected<'a, A: 'a + Send, B: 'a + Send, T: ?Sized + WeakFunctor<'a>> {
     A(A, T::F<B>),
     B(T::F<A>, B),
 }
@@ -10,17 +10,20 @@ pub type SelectedWrapped<'a, A, B, T> = Wrap<'a, Selected<'a, A, B, T>, T>;
 
 /// Part of [`Applicative`] responsible for choosing the first value.
 pub trait ApplicativeSelect<'a>: Functor<'a> {
-    fn select<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> SelectedWrapped<'a, A, B, Self> {
+    fn select<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        fb: Self::F<B>,
+    ) -> SelectedWrapped<'a, A, B, Self> {
         Self::fmap(fa, |a| Selected::A(a, fb))
     }
 }
 
 pub trait ApplicativeSelectExt<'a>: ApplicativeSelect<'a> {
     /// Shorthand for [`Functor::fmap`]&#8728;[`ApplicativeSelect::select`].
-    fn select_map<A: 'a, B: 'a, C: 'a>(
+    fn select_map<A: 'a + Send, B: 'a + Send, C: 'a + Send>(
         fa: Self::F<A>,
         fb: Self::F<B>,
-        f: impl 'a + FnOnce(Selected<'a, A, B, Self>) -> C,
+        f: impl 'a + Send + FnOnce(Selected<'a, A, B, Self>) -> C,
     ) -> Self::F<C> {
         Self::fmap(Self::select(fa, fb), f)
     }

src/func/context.rs

@@ -2,28 +2,31 @@ use super::{fail::*, *};
 
 pub type WrapC<'a, A, Ctx> = Wrap<'a, A, <Ctx as FunctorContext<'a>>::T>;
 
-pub trait FunctorContext<'a>: 'a {
+pub trait FunctorContext<'a>: 'a + Send {
     type T: WeakFunctor<'a>;
 }
 
 pub trait FunctorContextExt<'a>: FunctorContext<'a> {
-    fn fmap<A: 'a, B: 'a>(fa: WrapC<'a, A, Self>, f: impl 'a + FnOnce(A) -> B) -> WrapC<'a, B, Self>
+    fn fmap<A: 'a + Send, B: 'a + Send>(
+        fa: WrapC<'a, A, Self>,
+        f: impl 'a + Send + FnOnce(A) -> B,
+    ) -> WrapC<'a, B, Self>
     where
         Self::T: Functor<'a>,
     {
         <Self::T as Functor>::fmap(fa, f)
     }
 
-    fn pure<A: 'a>(a: A) -> WrapC<'a, A, Self>
+    fn pure<A: 'a + Send>(a: A) -> WrapC<'a, A, Self>
     where
         Self::T: Pure<'a>,
     {
         <Self::T as Pure>::pure(a)
     }
 
-    fn bind<A: 'a, B: 'a>(
+    fn bind<A: 'a + Send, B: 'a + Send>(
         fa: WrapC<'a, A, Self>,
-        f: impl 'a + FnOnce(A) -> WrapC<'a, B, Self>,
+        f: impl 'a + Send + FnOnce(A) -> WrapC<'a, B, Self>,
     ) -> WrapC<'a, B, Self>
     where
         Self::T: Monad<'a>,
@@ -31,7 +34,7 @@ pub trait FunctorContextExt<'a>: FunctorContext<'a> {
         <Self::T as Monad>::bind(fa, f)
     }
 
-    fn fail<A: 'a, E: 'a>(e: E) -> WrapC<'a, A, Self>
+    fn fail<A: 'a + Send, E: 'a + Send>(e: E) -> WrapC<'a, A, Self>
     where
         Self::T: Fail<'a, E>,
     {
@@ -58,12 +61,16 @@ pub type FallibleWrapped<'a, Ctx, A, E> = Wrap<'a, A, FallibleMonad<'a, Ctx, E>>
 /// this is the preferred way to switch between [WrapC] and [FallibleWrapped].
 pub trait FallibleCtxExt<'a>: FallibleCtx<'a> {
     /// Convert a fallible wrapped into a wrapped result.
-    fn unstuff<A: 'a, E: 'a>(wa: FallibleWrapped<'a, Self, A, E>) -> WrapC<'a, Result<A, E>, Self> {
+    fn unstuff<A: 'a + Send, E: 'a + Send>(
+        wa: FallibleWrapped<'a, Self, A, E>,
+    ) -> WrapC<'a, Result<A, E>, Self> {
         Self::Fallible::unstuff(wa)
     }
 
     /// Convert a wrapped result into a fallible wrapped.
-    fn stuff<A: 'a, E: 'a>(fa: WrapC<'a, Result<A, E>, Self>) -> FallibleWrapped<'a, Self, A, E> {
+    fn stuff<A: 'a + Send, E: 'a + Send>(
+        fa: WrapC<'a, Result<A, E>, Self>,
+    ) -> FallibleWrapped<'a, Self, A, E> {
         Self::Fallible::stuff(fa)
     }
 }

src/func/controlflow.rs

@@ -6,14 +6,14 @@ use super::{weakfunctorany::WeakFunctorAny, Functor, Pure, WeakFunctor, Wrap};
 
 pub(super) struct ControlFlowInstance<C>(ControlFlow<(), C>);
 
-impl<C> WeakFunctorAny for ControlFlowInstance<C> {
-    type FAny<'a, A: 'a> =  ControlFlow<A, C>
+impl<C: Send> WeakFunctorAny for ControlFlowInstance<C> {
+    type FAny<'a, A: 'a + Send> =  ControlFlow<A, C>
     where
         Self: 'a;
 }
 
-impl<'a, C: 'a> Functor<'a> for ControlFlowInstance<C> {
-    fn fmap<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> B) -> Self::F<B> {
+impl<'a, C: 'a + Send> Functor<'a> for ControlFlowInstance<C> {
+    fn fmap<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> B) -> Self::F<B> {
         match fa {
             ControlFlow::Continue(c) => ControlFlow::Continue(c),
             ControlFlow::Break(a) => ControlFlow::Break(f(a)),
@@ -21,24 +21,34 @@ impl<'a, C: 'a> Functor<'a> for ControlFlowInstance<C> {
     }
 }
 
-impl<'a, C: 'a> Pure<'a> for ControlFlowInstance<C> {
-    fn pure<A: 'a>(a: A) -> Self::F<A> {
+impl<'a, C: 'a + Send> Pure<'a> for ControlFlowInstance<C> {
+    fn pure<A: 'a + Send>(a: A) -> Self::F<A> {
         ControlFlow::Break(a)
     }
 }
 
 pub struct BindableMut<T: ?Sized, A, B, F>(A, F, PhantomData<B>, PhantomData<T>);
 
-impl<'a, T: ?Sized + Functor<'a>, A: 'a, B: 'a, F: 'a + FnMut(A) -> T::F<ControlFlow<B, A>>>
-    BindableMut<T, A, B, F>
+impl<
+        'a,
+        T: ?Sized + Functor<'a>,
+        A: 'a + Send,
+        B: 'a + Send,
+        F: 'a + Send + FnMut(A) -> T::F<ControlFlow<B, A>>,
+    > BindableMut<T, A, B, F>
 {
     pub fn new(a: A, f: F) -> Self {
         BindableMut(a, f, PhantomData, PhantomData)
     }
 }
 
-impl<'a, T: ?Sized + Functor<'a>, A: 'a, B: 'a, F: 'a + FnMut(A) -> T::F<ControlFlow<B, A>>>
-    Iterative<'a> for BindableMut<T, A, B, F>
+impl<
+        'a,
+        T: ?Sized + Functor<'a>,
+        A: 'a + Send,
+        B: 'a + Send,
+        F: 'a + Send + FnMut(A) -> T::F<ControlFlow<B, A>>,
+    > Iterative<'a> for BindableMut<T, A, B, F>
 {
     type B = B;
     type T = T;
@@ -58,9 +68,9 @@ pub type IterativeWrapped<'a, F> =
 /// Value passed to [`Monad::iterate`].
 ///
 /// [`Monad::iterate`]: super::Monad::iterate
-pub trait Iterative<'a>: 'a + Sized {
+pub trait Iterative<'a>: 'a + Send + Sized {
     /// [`ControlFlow::Break`].
-    type B: 'a;
+    type B: 'a + Send;
     /// Corresponding [`WeakFunctor`].
     type T: ?Sized + WeakFunctor<'a>;
     /// Get next state.

src/func/derivations.rs

@@ -3,22 +3,22 @@
 use super::*;
 
 /// Equivalent of Haskell's `fmap`. `function-function` equivalent of [Functor::fmap].
-pub fn fmap<'a, T: Functor<'a>, A: 'a, B: 'a>(
-    f: impl 'a + FnOnce(A) -> B,
+pub fn fmap<'a, T: Functor<'a>, A: 'a + Send, B: 'a + Send>(
+    f: impl 'a + Send + FnOnce(A) -> B,
 ) -> impl FnOnce(Wrap<'a, A, T>) -> Wrap<'a, B, T> {
     move |fa| T::fmap(fa, f)
 }
 
 /// Equivalent of Haskell's `fmap`. `function-function` equivalent of [Monad::bind].
-pub fn bind<'a, T: Monad<'a>, A: 'a, B: 'a>(
-    f: impl 'a + FnOnce(A) -> T::F<B>,
+pub fn bind<'a, T: Monad<'a>, A: 'a + Send, B: 'a + Send>(
+    f: impl 'a + Send + FnOnce(A) -> T::F<B>,
 ) -> impl FnOnce(Wrap<'a, A, T>) -> Wrap<'a, B, T> {
     move |fa| T::bind(fa, f)
 }
 
 pub trait ApplicativeLA2ViaSeq<'a>: ApplicativeSeq<'a> {
-    fn _la2_via_seq<A: 'a, B: 'a, C: 'a>(
-        f: impl 'a + FnOnce(A, B) -> C,
+    fn _la2_via_seq<A: 'a + Send, B: 'a + Send, C: 'a + Send>(
+        f: impl 'a + Send + FnOnce(A, B) -> C,
         fa: Self::F<A>,
         fb: Self::F<B>,
     ) -> Self::F<C> {
@@ -29,8 +29,8 @@ pub trait ApplicativeLA2ViaSeq<'a>: ApplicativeSeq<'a> {
 impl<'a, T: ApplicativeSeq<'a>> ApplicativeLA2ViaSeq<'a> for T {}
 
 pub trait ApplicativeSeqViaLA2<'a>: ApplicativeLA2<'a> {
-    fn _seq_via_la2<A: 'a, B: 'a>(
-        ff: Self::F<impl 'a + FnOnce(A) -> B>,
+    fn _seq_via_la2<A: 'a + Send, B: 'a + Send>(
+        ff: Self::F<impl 'a + Send + FnOnce(A) -> B>,
         fa: Self::F<A>,
     ) -> Self::F<B> {
         Self::la2(ff, fa, |f, a| f(a))
@@ -40,7 +40,9 @@ pub trait ApplicativeSeqViaLA2<'a>: ApplicativeLA2<'a> {
 impl<'a, T: ApplicativeLA2<'a>> ApplicativeSeqViaLA2<'a> for T {}
 
 pub trait ApplicativeTupleViaLA2<'a>: ApplicativeLA2<'a> {
-    fn _tuple_via_la2<A: 'a, B: 'a>((fa, fb): (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
+    fn _tuple_via_la2<A: 'a + Send, B: 'a + Send>(
+        (fa, fb): (Self::F<A>, Self::F<B>),
+    ) -> Self::F<(A, B)> {
         Self::la2(fa, fb, |a, b| (a, b))
     }
 }

src/func/extensions.rs

@@ -5,17 +5,17 @@ pub trait MonadExt<'a>: Monad<'a> {
     /// Reasoning for this method existing at all is that
     /// most usecases are better modelled with [`FnMut`]
     /// rather than some dedicated state type.
-    fn iterate_mut<A: 'a, B: 'a>(
+    fn iterate_mut<A: 'a + Send, B: 'a + Send>(
         a: A,
-        f: impl 'a + FnMut(A) -> Self::F<ControlFlow<B, A>>,
+        f: impl 'a + Send + FnMut(A) -> Self::F<ControlFlow<B, A>>,
     ) -> Self::F<B> {
         Self::iterate(BindableMut::new(a, f))
     }
 
-    fn bind2<A: 'a, B: 'a, C: 'a>(
+    fn bind2<A: 'a + Send, B: 'a + Send, C: 'a + Send>(
         fa: Self::F<A>,
         fb: Self::F<B>,
-        f: impl 'a + FnOnce(A, B) -> Self::F<C>,
+        f: impl 'a + Send + FnOnce(A, B) -> Self::F<C>,
     ) -> Self::F<C> {
         Self::join(Self::la2(fa, fb, f))
     }

src/func/fail.rs

@@ -1,44 +1,46 @@
 use super::*;
 
 /// Part of [`MonadFail`] responsible for Haskell's `fail`.
-pub trait Fail<'a, E: 'a>: WeakFunctor<'a> {
+pub trait Fail<'a, E: 'a + Send>: WeakFunctor<'a> {
     /// Equivalent of Haskell's `fail`.
-    fn fail<A: 'a>(e: E) -> Self::F<A>;
+    fn fail<A: 'a + Send>(e: E) -> Self::F<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<'a, E: 'a>: Monad<'a> + Fail<'a, E> {}
+pub trait MonadFail<'a, E: 'a + Send>: Monad<'a> + Fail<'a, E> {}
 
-impl<'a, E: 'a, T: Monad<'a> + Fail<'a, E>> MonadFail<'a, E> for T {}
+impl<'a, E: 'a + Send, T: Monad<'a> + Fail<'a, E>> MonadFail<'a, E> for T {}
 
 /// Represents a (collection of) [Monad]\(s) that can hold any type of error.
-pub trait MonadFailAny<'a>: 'a {
+pub trait MonadFailAny<'a>: 'a + Send {
     /// [`MonadFail`] for a specific error type.
-    type W<E>: MonadFail<'a, E>
-    where
-        E: 'a;
+    type W<E: 'a + Send>: MonadFail<'a, E>;
 
     /// Associated infallible [`Monad`].
     type T: Monad<'a>;
 
-    fn unstuff<A: 'a, E: 'a>(wa: WrapE<'a, A, E, Self>) -> Wrap<'a, Result<A, E>, Self::T>;
+    fn unstuff<A: 'a + Send, E: 'a + Send>(
+        wa: WrapE<'a, A, E, Self>,
+    ) -> Wrap<'a, Result<A, E>, Self::T>;
 
-    fn stuff<A: 'a, E: 'a>(fa: Wrap<'a, Result<A, E>, Self::T>) -> WrapE<'a, A, E, Self>;
+    fn stuff<A: 'a + Send, E: 'a + Send>(
+        fa: Wrap<'a, Result<A, E>, Self::T>,
+    ) -> WrapE<'a, A, E, Self>;
 
     /// Equivalent of [`Result::map_err`].
-    fn map_err<A: 'a, E0: 'a, E1: 'a>(
+    fn map_err<A: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, A, E0, Self>,
-        f: impl 'a + FnOnce(E0) -> E1,
+        f: impl 'a + Send + FnOnce(E0) -> E1,
     ) -> WrapE<'a, A, E1, Self> {
         Self::bind_err(wa, |e0| Self::fail(f(e0)))
     }
 
     /// Equivalent of `catch`/`except`. To inject errors on success, see [`MonadFailAny::bind`].
-    fn bind_err<A: 'a, E0: 'a, E1: 'a>(
+    fn bind_err<A: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, A, E0, Self>,
-        f: impl 'a + FnOnce(E0) -> WrapE<'a, A, E1, Self>,
+        f: impl 'a + Send + FnOnce(E0) -> WrapE<'a, A, E1, Self>,
     ) -> WrapE<'a, A, E1, Self> {
         Self::bind(wa, |result| match result {
             Ok(a) => Self::pure(a),
@@ -51,9 +53,9 @@ pub trait MonadFailAny<'a>: 'a {
     ///
     /// Note: Reasonably it is expected to lack fail semantics for the underlying result.
     /// Therefore the default implementation descends into the non-fail monad [`MonadFailAny::T`].
-    fn bind<A: 'a, B: 'a, E0: 'a, E1: 'a>(
+    fn bind<A: 'a + Send, B: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, A, E0, Self>,
-        f: impl 'a + FnOnce(Result<A, E0>) -> WrapE<'a, B, E1, Self>,
+        f: impl 'a + Send + FnOnce(Result<A, E0>) -> WrapE<'a, B, E1, Self>,
     ) -> WrapE<'a, B, E1, Self> {
         Self::stuff(<Self::T as Monad>::bind(Self::unstuff(wa), |result| {
             Self::unstuff(f(result))
@@ -63,7 +65,7 @@ pub trait MonadFailAny<'a>: 'a {
     /// Equivalent of [`Monad::join`], flattening the errors.
     ///
     /// Note: default implementation doesn't depend on [`Monad::join`].
-    fn join<A: 'a, E0: 'a, E1: 'a>(
+    fn join<A: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wwa: WrapE<'a, WrapE<'a, A, E0, Self>, E1, Self>,
     ) -> WrapE<'a, A, Result<E0, E1>, Self> {
         Self::bind(wwa, |result| match result {
@@ -73,7 +75,7 @@ pub trait MonadFailAny<'a>: 'a {
     }
 
     /// Lift the error.
-    fn rotate_out<A: 'a, E0: 'a, E1: 'a>(
+    fn rotate_out<A: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, Result<A, E1>, E0, Self>,
     ) -> WrapE<'a, A, Result<E1, E0>, Self> {
         <Self::W<Result<E1, E0>> as Monad>::bind(Self::map_err(wa, Err), |fa| match fa {
@@ -86,11 +88,11 @@ pub trait MonadFailAny<'a>: 'a {
 pub type WrapE<'a, A, E, Fallible> = Wrap<'a, A, <Fallible as MonadFailAny<'a>>::W<E>>;
 
 pub trait MonadFailAnyExt<'a>: MonadFailAny<'a> {
-    fn pure<E: 'a, A: 'a>(a: A) -> WrapE<'a, A, E, Self> {
+    fn pure<E: 'a + Send, A: 'a + Send>(a: A) -> WrapE<'a, A, E, Self> {
         <Self::W<E> as Pure>::pure(a)
     }
 
-    fn fail<E: 'a, A: 'a>(e: E) -> WrapE<'a, A, E, Self> {
+    fn fail<E: 'a + Send, A: 'a + Send>(e: E) -> WrapE<'a, A, E, Self> {
         <Self::W<E> as Fail<E>>::fail(e)
     }
 }

src/func/instances/composition.rs

@@ -14,25 +14,28 @@ use crate::func::class_prelude::*;
 pub struct CompositionInstance<U, V>(U, V);
 
 impl<'a, U: WeakFunctor<'a>, V: WeakFunctor<'a>> WeakFunctor<'a> for CompositionInstance<U, V> {
-    type F<A: 'a> = U::F<V::F<A>>;
+    type F<A: 'a + Send> = U::F<V::F<A>>;
 }
 
 impl<'a, U: Functor<'a>, V: Functor<'a>> Functor<'a> for CompositionInstance<U, V> {
-    fn fmap<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> B) -> Self::F<B> {
+    fn fmap<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + Send + FnOnce(A) -> B,
+    ) -> Self::F<B> {
         U::fmap(fa, |ua| V::fmap(ua, f))
     }
 
-    fn replace<A: 'a, B: 'a>(fa: Self::F<A>, b: B) -> Self::F<B> {
+    fn replace<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, b: B) -> Self::F<B> {
         U::fmap(fa, |ua| V::replace(ua, b))
     }
 
-    fn void<A: 'a>(fa: Self::F<A>) -> Self::F<()> {
+    fn void<A: 'a + Send>(fa: Self::F<A>) -> Self::F<()> {
         U::fmap(fa, |ua| V::void(ua))
     }
 }
 
 impl<'a, U: Pure<'a>, V: Pure<'a>> Pure<'a> for CompositionInstance<U, V> {
-    fn pure<A: 'a>(a: A) -> Self::F<A> {
+    fn pure<A: 'a + Send>(a: A) -> Self::F<A> {
         U::pure(V::pure(a))
     }
 }
@@ -41,7 +44,10 @@ impl<'a, U: Pure<'a>, V: Pure<'a>> Pure<'a> for CompositionInstance<U, V> {
 impl<'a, U: ApplicativeLA2<'a>, V: ApplicativeSeq<'a>> ApplicativeSeq<'a>
     for CompositionInstance<U, V>
 {
-    fn seq<A: 'a, B: 'a>(ff: Self::F<impl 'a + FnOnce(A) -> B>, fa: Self::F<A>) -> Self::F<B> {
+    fn seq<A: 'a + Send, B: 'a + Send>(
+        ff: Self::F<impl 'a + Send + FnOnce(A) -> B>,
+        fa: Self::F<A>,
+    ) -> Self::F<B> {
         U::la2(ff, fa, V::seq)
     }
 }
@@ -49,10 +55,10 @@ impl<'a, U: ApplicativeLA2<'a>, V: ApplicativeSeq<'a>> ApplicativeSeq<'a>
 impl<'a, U: ApplicativeLA2<'a>, V: ApplicativeLA2<'a>> ApplicativeLA2<'a>
     for CompositionInstance<U, V>
 {
-    fn la2<A: 'a, B: 'a, C: 'a>(
+    fn la2<A: 'a + Send, B: 'a + Send, C: 'a + Send>(
         fa: Self::F<A>,
         fb: Self::F<B>,
-        f: impl 'a + FnOnce(A, B) -> C,
+        f: impl 'a + Send + FnOnce(A, B) -> C,
     ) -> Self::F<C> {
         U::la2(fa, fb, |ua, ub| V::la2(ua, ub, f))
     }
@@ -61,7 +67,7 @@ impl<'a, U: ApplicativeLA2<'a>, V: ApplicativeLA2<'a>> ApplicativeLA2<'a>
 impl<'a, U: ApplicativeTuple<'a>, V: ApplicativeTuple<'a>> ApplicativeTuple<'a>
     for CompositionInstance<U, V>
 {
-    fn tuple<A: 'a, B: 'a>(fab: (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
+    fn tuple<A: 'a + Send, B: 'a + Send>(fab: (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
         U::fmap(U::tuple(fab), V::tuple)
     }
 }
@@ -70,7 +76,10 @@ impl<'a, U: ApplicativeTuple<'a>, V: ApplicativeTuple<'a>> ApplicativeTuple<'a>
 impl<'a, U: ApplicativeSelect<'a>, V: Functor<'a>> ApplicativeSelect<'a>
     for CompositionInstance<U, V>
 {
-    fn select<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> SelectedWrapped<'a, A, B, Self> {
+    fn select<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        fb: Self::F<B>,
+    ) -> SelectedWrapped<'a, A, B, Self> {
         U::fmap(U::select(fa, fb), |selected| match selected {
             Selected::A(ua, fb) => V::fmap(ua, |a| Selected::A(a, fb)),
             Selected::B(fa, ub) => V::fmap(ub, |b| Selected::B(fa, b)),
@@ -79,21 +88,24 @@ impl<'a, U: ApplicativeSelect<'a>, V: Functor<'a>> ApplicativeSelect<'a>
 }
 
 impl<'a, U: Applicative<'a>, V: Applicative<'a>> Applicative<'a> for CompositionInstance<U, V> {
-    fn discard_first<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
+    fn discard_first<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
         U::la2(fa, fb, V::discard_first)
     }
 
-    fn discard_second<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
+    fn discard_second<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
         U::la2(fa, fb, V::discard_second)
     }
 }
 
 impl<'a, U: Monad<'a>, V: Monad<'a> + LocalFunctor<'a>> Monad<'a> for CompositionInstance<U, V> {
-    fn bind<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> Self::F<B>) -> Self::F<B> {
+    fn bind<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + Send + FnOnce(A) -> Self::F<B>,
+    ) -> Self::F<B> {
         U::bind(fa, |ua| U::fmap(V::stuff::<_, U>(V::fmap(ua, f)), V::join))
     }
 
-    fn iterate<B: 'a>(f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
+    fn iterate<B: 'a + Send>(f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
         U::iterate(ComposedIterative(f))
     }
 
@@ -104,7 +116,7 @@ impl<'a, U: Monad<'a>, V: Monad<'a> + LocalFunctor<'a>> Monad<'a> for Compositio
     /// U U V V A
     ///  U   V  A
     /// ```
-    fn join<A: 'a>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
+    fn join<A: 'a + Send>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
         U::join(U::fmap(ffa, |ufa| U::fmap(V::stuff::<_, U>(ufa), V::join)))
     }
 }
@@ -129,10 +141,10 @@ where
 }
 
 /// Note: fails in the inner instance not outer.
-impl<'a, E: 'a, U: Monad<'a>, V: Fail<'a, E> + LocalFunctor<'a>> Fail<'a, E>
+impl<'a, E: 'a + Send, U: Monad<'a>, V: Fail<'a, E> + LocalFunctor<'a>> Fail<'a, E>
     for CompositionInstance<U, V>
 {
-    fn fail<A: 'a>(e: E) -> Self::F<A> {
+    fn fail<A: 'a + Send>(e: E) -> Self::F<A> {
         U::pure(V::fail(e))
     }
 }
@@ -140,11 +152,13 @@ impl<'a, E: 'a, U: Monad<'a>, V: Fail<'a, E> + LocalFunctor<'a>> Fail<'a, E>
 impl<'a, U: LocalFunctor<'a> + Functor<'a>, V: LocalFunctor<'a>> LocalFunctor<'a>
     for CompositionInstance<U, V>
 {
-    fn unstuff<A: 'a, B: 'a>(state: Self::F<ControlFlow<B, A>>) -> ControlFlow<Self::F<B>, A> {
+    fn unstuff<A: 'a + Send, B: 'a + Send>(
+        state: Self::F<ControlFlow<B, A>>,
+    ) -> ControlFlow<Self::F<B>, A> {
         U::unstuff(U::fmap(state, V::unstuff))
     }
 
-    fn stuff<A: 'a, T: Pure<'a>>(fa: Self::F<T::F<A>>) -> T::F<Self::F<A>> {
+    fn stuff<A: 'a + Send, T: Pure<'a>>(fa: Self::F<T::F<A>>) -> T::F<Self::F<A>> {
         U::stuff::<_, T>(U::fmap(fa, V::stuff::<_, T>))
     }
 }
@@ -152,13 +166,13 @@ impl<'a, U: LocalFunctor<'a> + Functor<'a>, V: LocalFunctor<'a>> LocalFunctor<'a
 impl<'a, U: SharedFunctor<'a> + Functor<'a>, V: SharedFunctor<'a>> SharedFunctor<'a>
     for CompositionInstance<U, V>
 {
-    type Shared<A: 'a + Clone> = U::Shared<V::Shared<A>>;
+    type Shared<A: 'a + Send + Sync + Clone> = U::Shared<V::Shared<A>>;
 
-    fn share<A: 'a + Clone>(fa: Self::F<A>) -> Self::Shared<A> {
+    fn share<A: 'a + Send + Sync + Clone>(fa: Self::F<A>) -> Self::Shared<A> {
         U::share(U::fmap(fa, V::share))
     }
 
-    fn unshare<A: 'a + Clone>(sa: Self::Shared<A>) -> Self::F<A> {
+    fn unshare<A: 'a + Send + Sync + Clone>(sa: Self::Shared<A>) -> Self::F<A> {
         U::fmap(U::unshare(sa), V::unshare)
     }
 }

src/func/instances/effect.rs

@@ -10,7 +10,7 @@
 use crate::func::class_prelude::*;
 
 /// Metadata type.
-pub trait Effect {
+pub trait Effect: Send {
     /// Used in [`Pure::pure`].
     fn e_pure() -> Self;
 
@@ -37,24 +37,43 @@ impl<A, E: Effect> WithEffect<A, E> {
     }
 }
 
-#[derive(SharedFunctorAny)]
-pub struct EffectInstance<E>(E);
+pub struct EffectInstance<E: Send>(E);
 
-impl<E> WeakFunctorAny for EffectInstance<E> {
-    type FAny<'a, A: 'a> = WithEffect<A, E>
+impl<E: Send + Sync + Clone> SharedFunctorAny for EffectInstance<E> {
+    type SharedAny<'a, A: 'a + Send + Sync + Clone> = Self::FAny<'a, A>
+    where
+        Self: 'a;
+
+    fn share<'a, A: 'a + Send + Sync + Clone>(fa: Self::FAny<'a, A>) -> Self::SharedAny<'a, A>
+    where
+        Self: 'a,
+    {
+        fa
+    }
+
+    fn unshare<'a, A: 'a + Send + Sync + Clone>(sa: Self::SharedAny<'a, A>) -> Self::FAny<'a, A>
+    where
+        Self: 'a,
+    {
+        sa
+    }
+}
+
+impl<E: Send> WeakFunctorAny for EffectInstance<E> {
+    type FAny<'a, A: 'a + Send> = WithEffect<A, E>
     where
         Self: 'a;
 }
 
-impl<'a, E: 'a> Functor<'a> for EffectInstance<E> {
-    fn fmap<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> B) -> Self::F<B> {
+impl<'a, E: 'a + Send> Functor<'a> for EffectInstance<E> {
+    fn fmap<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> B) -> Self::F<B> {
         WithEffect {
             value: f(fa.value),
             effect: fa.effect,
         }
     }
 
-    fn replace<A: 'a, B: 'a>(fa: Self::F<A>, b: B) -> Self::F<B> {
+    fn replace<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, b: B) -> Self::F<B> {
         drop(fa.value);
         WithEffect {
             value: b,
@@ -64,7 +83,7 @@ impl<'a, E: 'a> Functor<'a> for EffectInstance<E> {
 }
 
 impl<'a, E: 'a + Effect> Pure<'a> for EffectInstance<E> {
-    fn pure<A: 'a>(a: A) -> Self::F<A> {
+    fn pure<A: 'a + Send>(a: A) -> Self::F<A> {
         WithEffect {
             value: a,
             effect: E::e_pure(),
@@ -73,7 +92,10 @@ impl<'a, E: 'a + Effect> Pure<'a> for EffectInstance<E> {
 }
 
 impl<'a, E: 'a + Effect> ApplicativeSeq<'a> for EffectInstance<E> {
-    fn seq<A: 'a, B: 'a>(ff: Self::F<impl 'a + FnOnce(A) -> B>, fa: Self::F<A>) -> Self::F<B> {
+    fn seq<A: 'a + Send, B: 'a + Send>(
+        ff: Self::F<impl 'a + Send + FnOnce(A) -> B>,
+        fa: Self::F<A>,
+    ) -> Self::F<B> {
         WithEffect {
             value: (ff.value)(fa.value),
             effect: E::e_seq(ff.effect, fa.effect),
@@ -82,10 +104,10 @@ impl<'a, E: 'a + Effect> ApplicativeSeq<'a> for EffectInstance<E> {
 }
 
 impl<'a, E: 'a + Effect> ApplicativeLA2<'a> for EffectInstance<E> {
-    fn la2<A: 'a, B: 'a, C: 'a>(
+    fn la2<A: 'a + Send, B: 'a + Send, C: 'a + Send>(
         fa: Self::F<A>,
         fb: Self::F<B>,
-        f: impl 'a + FnOnce(A, B) -> C,
+        f: impl 'a + Send + FnOnce(A, B) -> C,
     ) -> Self::F<C> {
         WithEffect {
             value: f(fa.value, fb.value),
@@ -95,7 +117,7 @@ impl<'a, E: 'a + Effect> ApplicativeLA2<'a> for EffectInstance<E> {
 }
 
 impl<'a, E: 'a + Effect> ApplicativeTuple<'a> for EffectInstance<E> {
-    fn tuple<A: 'a, B: 'a>((fa, fb): (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
+    fn tuple<A: 'a + Send, B: 'a + Send>((fa, fb): (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
         WithEffect {
             value: (fa.value, fb.value),
             effect: E::e_seq(fa.effect, fb.effect),
@@ -106,7 +128,7 @@ impl<'a, E: 'a + Effect> ApplicativeTuple<'a> for EffectInstance<E> {
 impl<'a, E: 'a + Effect> ApplicativeSelect<'a> for EffectInstance<E> {}
 
 impl<'a, E: 'a + Effect> Applicative<'a> for EffectInstance<E> {
-    fn discard_first<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
+    fn discard_first<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
         drop(fa.value);
         WithEffect {
             value: fb.value,
@@ -114,7 +136,7 @@ impl<'a, E: 'a + Effect> Applicative<'a> for EffectInstance<E> {
         }
     }
 
-    fn discard_second<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
+    fn discard_second<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
         drop(fb.value);
         WithEffect {
             value: fa.value,
@@ -124,11 +146,14 @@ impl<'a, E: 'a + Effect> Applicative<'a> for EffectInstance<E> {
 }
 
 impl<'a, E: 'a + Effect> Monad<'a> for EffectInstance<E> {
-    fn bind<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> Self::F<B>) -> Self::F<B> {
+    fn bind<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + FnOnce(A) -> Self::F<B>,
+    ) -> Self::F<B> {
         f(fa.value).e_after(fa.effect)
     }
 
-    fn iterate<B: 'a>(mut f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
+    fn iterate<B: 'a + Send>(mut f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
         let mut effect = E::e_pure();
         loop {
             let fa = f.next();
@@ -140,13 +165,13 @@ impl<'a, E: 'a + Effect> Monad<'a> for EffectInstance<E> {
         }
     }
 
-    fn join<A: 'a>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
+    fn join<A: 'a + Send>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
         ffa.value.e_after(ffa.effect)
     }
 }
 
-impl<'a, E: 'a> LocalFunctor<'a> for EffectInstance<E> {
-    fn stuff<A: 'a, T: Pure<'a>>(fa: Self::F<T::F<A>>) -> T::F<Self::F<A>> {
+impl<'a, E: 'a + Send> LocalFunctor<'a> for EffectInstance<E> {
+    fn stuff<A: 'a + Send, T: Pure<'a>>(fa: Self::F<T::F<A>>) -> T::F<Self::F<A>> {
         T::fmap(fa.value, |a| WithEffect {
             value: a,
             effect: fa.effect,

src/func/instances/future.rs

@@ -21,15 +21,18 @@ use crate::func::class_prelude::*;
 pub struct FutureInstance;
 
 impl WeakFunctorAny for FutureInstance {
-    type FAny<'a, A: 'a> = Pin<Box<dyn 'a + Future<Output = A>>>;
+    type FAny<'a, A: 'a + Send> = Pin<Box<dyn 'a + Send + Future<Output = A>>>;
 }
 
 impl<'a> Functor<'a> for FutureInstance {
-    fn fmap<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> B) -> Self::F<B> {
+    fn fmap<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + Send + FnOnce(A) -> B,
+    ) -> Self::F<B> {
         Box::pin(async { f(fa.await) })
     }
 
-    fn replace<A: 'a, B: 'a>(fa: Self::F<A>, b: B) -> Self::F<B> {
+    fn replace<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, b: B) -> Self::F<B> {
         Box::pin(async {
             fa.await;
             b
@@ -38,13 +41,16 @@ impl<'a> Functor<'a> for FutureInstance {
 }
 
 impl<'a> Pure<'a> for FutureInstance {
-    fn pure<A: 'a>(a: A) -> Self::F<A> {
+    fn pure<A: 'a + Send>(a: A) -> Self::F<A> {
         Box::pin(async { a })
     }
 }
 
 impl<'a> ApplicativeSeq<'a> for FutureInstance {
-    fn seq<A: 'a, B: 'a>(ff: Self::F<impl 'a + FnOnce(A) -> B>, fa: Self::F<A>) -> Self::F<B> {
+    fn seq<A: 'a + Send, B: 'a + Send>(
+        ff: Self::F<impl 'a + Send + FnOnce(A) -> B>,
+        fa: Self::F<A>,
+    ) -> Self::F<B> {
         Box::pin(async {
             let (f, a) = join!(ff, fa);
             f(a)
@@ -53,10 +59,10 @@ impl<'a> ApplicativeSeq<'a> for FutureInstance {
 }
 
 impl<'a> ApplicativeLA2<'a> for FutureInstance {
-    fn la2<A: 'a, B: 'a, C: 'a>(
+    fn la2<A: 'a + Send, B: 'a + Send, C: 'a + Send>(
         fa: Self::F<A>,
         fb: Self::F<B>,
-        f: impl 'a + FnOnce(A, B) -> C,
+        f: impl 'a + Send + FnOnce(A, B) -> C,
     ) -> Self::F<C> {
         Box::pin(async {
             let (a, b) = join!(fa, fb);
@@ -66,13 +72,16 @@ impl<'a> ApplicativeLA2<'a> for FutureInstance {
 }
 
 impl<'a> ApplicativeTuple<'a> for FutureInstance {
-    fn tuple<A: 'a, B: 'a>((fa, fb): (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
+    fn tuple<A: 'a + Send, B: 'a + Send>((fa, fb): (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
         Box::pin(join(fa, fb))
     }
 }
 
 impl<'a> ApplicativeSelect<'a> for FutureInstance {
-    fn select<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> SelectedWrapped<'a, A, B, Self> {
+    fn select<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        fb: Self::F<B>,
+    ) -> SelectedWrapped<'a, A, B, Self> {
         Box::pin(async {
             match select(fa, fb).await {
                 Either::Left((a, fb)) => Selected::A(a, fb),
@@ -83,21 +92,24 @@ impl<'a> ApplicativeSelect<'a> for FutureInstance {
 }
 
 impl<'a> Applicative<'a> for FutureInstance {
-    fn discard_first<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
+    fn discard_first<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
         Box::pin(async { join!(fa, fb).1 })
     }
 
-    fn discard_second<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
+    fn discard_second<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
         Box::pin(async { join!(fa, fb).0 })
     }
 }
 
 impl<'a> Monad<'a> for FutureInstance {
-    fn bind<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> Self::F<B>) -> Self::F<B> {
+    fn bind<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + Send + FnOnce(A) -> Self::F<B>,
+    ) -> Self::F<B> {
         Box::pin(async { f(fa.await).await })
     }
 
-    fn iterate<B: 'a>(mut f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
+    fn iterate<B: 'a + Send>(mut f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
         Box::pin(async move {
             loop {
                 match f.next().await {
@@ -108,19 +120,19 @@ impl<'a> Monad<'a> for FutureInstance {
         })
     }
 
-    fn join<A: 'a>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
+    fn join<A: 'a + Send>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
         Box::pin(async { ffa.await.await })
     }
 }
 
 impl<'a> SharedFunctor<'a> for FutureInstance {
-    type Shared<A: 'a + Clone> = Shared<Pin<Box<dyn 'a + Future<Output = A>>>>;
+    type Shared<A: 'a + Send + Sync + Clone> = Shared<Pin<Box<dyn 'a + Send + Future<Output = A>>>>;
 
-    fn share<A: 'a + Clone>(fa: Self::F<A>) -> Self::Shared<A> {
+    fn share<A: 'a + Send + Sync + Clone>(fa: Self::F<A>) -> Self::Shared<A> {
         fa.shared()
     }
 
-    fn unshare<A: 'a + Clone>(sa: Self::Shared<A>) -> Self::F<A> {
+    fn unshare<A: 'a + Send + Sync + Clone>(sa: Self::Shared<A>) -> Self::F<A> {
         Box::pin(sa)
     }
 }

src/func/instances/lazy.rs

@@ -9,56 +9,60 @@
 //!
 //! [`stackless`]: super::stackless
 
-use std::{cell::RefCell, rc::Rc};
-
 use crate::func::class_prelude::*;
 
 pub struct LazyInstance;
 
 impl WeakFunctorAny for LazyInstance {
-    type FAny<'a, A: 'a> = Box<dyn 'a + FnOnce() -> A>;
+    type FAny<'a, A: 'a + Send> = Box<dyn 'a + Send + FnOnce() -> A>;
 }
 
 impl<'a> Functor<'a> for LazyInstance {
-    fn fmap<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> B) -> Self::F<B> {
+    fn fmap<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + Send + FnOnce(A) -> B,
+    ) -> Self::F<B> {
         Box::new(|| f(fa()))
     }
 
-    fn replace<A: 'a, B: 'a>(fa: Self::F<A>, b: B) -> Self::F<B> {
+    fn replace<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, b: B) -> Self::F<B> {
         drop(fa);
         Box::new(|| b)
     }
 
-    fn void<A: 'a>(fa: Self::F<A>) -> Self::F<()> {
+    fn void<A: 'a + Send>(fa: Self::F<A>) -> Self::F<()> {
         drop(fa);
         Box::new(|| ())
     }
 }
 
 impl<'a> Pure<'a> for LazyInstance {
-    fn pure<A: 'a>(a: A) -> Self::F<A> {
+    fn pure<A: 'a + Send>(a: A) -> Self::F<A> {
         Box::new(|| a)
     }
 }
 
 impl<'a> ApplicativeSeq<'a> for LazyInstance {
-    fn seq<A: 'a, B: 'a>(ff: Self::F<impl 'a + FnOnce(A) -> B>, fa: Self::F<A>) -> Self::F<B> {
+    fn seq<A: 'a + Send, B: 'a + Send>(
+        ff: Self::F<impl 'a + Send + FnOnce(A) -> B>,
+        fa: Self::F<A>,
+    ) -> Self::F<B> {
         Box::new(|| ff()(fa()))
     }
 }
 
 impl<'a> ApplicativeLA2<'a> for LazyInstance {
-    fn la2<A: 'a, B: 'a, C: 'a>(
+    fn la2<A: 'a + Send, B: 'a + Send, C: 'a + Send>(
         fa: Self::F<A>,
         fb: Self::F<B>,
-        f: impl 'a + FnOnce(A, B) -> C,
+        f: impl 'a + Send + FnOnce(A, B) -> C,
     ) -> Self::F<C> {
         Box::new(|| f(fa(), fb()))
     }
 }
 
 impl<'a> ApplicativeTuple<'a> for LazyInstance {
-    fn tuple<A: 'a, B: 'a>((fa, fb): (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
+    fn tuple<A: 'a + Send, B: 'a + Send>((fa, fb): (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
         Box::new(|| (fa(), fb()))
     }
 }
@@ -66,23 +70,26 @@ impl<'a> ApplicativeTuple<'a> for LazyInstance {
 impl<'a> ApplicativeSelect<'a> for LazyInstance {}
 
 impl<'a> Applicative<'a> for LazyInstance {
-    fn discard_first<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
+    fn discard_first<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
         drop(fa);
         fb
     }
 
-    fn discard_second<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
+    fn discard_second<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
         drop(fb);
         fa
     }
 }
 
 impl<'a> Monad<'a> for LazyInstance {
-    fn bind<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> Self::F<B>) -> Self::F<B> {
+    fn bind<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + Send + FnOnce(A) -> Self::F<B>,
+    ) -> Self::F<B> {
         Box::new(|| f(fa())())
     }
 
-    fn iterate<B: 'a>(mut f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
+    fn iterate<B: 'a + Send>(mut f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
         loop {
             match f.next()() {
                 ControlFlow::Continue(next_f) => f = next_f,
@@ -91,28 +98,7 @@ impl<'a> Monad<'a> for LazyInstance {
         }
     }
 
-    fn join<A: 'a>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
+    fn join<A: 'a + Send>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
         Box::new(|| ffa()())
     }
 }
-
-fn unshare<'a, A: 'a + Clone>(shared: &mut Option<Box<dyn 'a + FnOnce() -> A>>) -> A {
-    let a = shared.take().expect(
-        "cannot evaluate a missing shared lazy value. probably, the shared value depends on itself",
-    )();
-    let cloned = a.clone();
-    *shared = Some(Box::new(|| cloned));
-    a
-}
-
-impl<'a> SharedFunctor<'a> for LazyInstance {
-    type Shared<A: 'a + Clone> = Rc<RefCell<Option<Box<dyn 'a + FnOnce() -> A>>>>;
-
-    fn share<A: 'a + Clone>(fa: Self::F<A>) -> Self::Shared<A> {
-        Rc::new(RefCell::new(Some(fa)))
-    }
-
-    fn unshare<A: 'a + Clone>(sa: Self::Shared<A>) -> Self::F<A> {
-        Box::new(move || unshare(&mut *sa.borrow_mut()))
-    }
-}

src/func/instances/option.rs

@@ -17,49 +17,55 @@ use crate::func::class_prelude::*;
 pub struct OptionInstance;
 
 impl WeakFunctorAny for OptionInstance {
-    type FAny<'a, A: 'a> = Option<A>;
+    type FAny<'a, A: 'a + Send> = Option<A>;
 }
 
 impl<'a> Functor<'a> for OptionInstance {
-    fn fmap<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> B) -> Self::F<B> {
+    fn fmap<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + Send + FnOnce(A) -> B,
+    ) -> Self::F<B> {
         fa.map(f)
     }
 
-    fn replace<A: 'a, B: 'a>(fa: Self::F<A>, b: B) -> Self::F<B> {
+    fn replace<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, b: B) -> Self::F<B> {
         fa?;
         Self::pure(b)
     }
 
-    fn void<A: 'a>(fa: Self::F<A>) -> Self::F<()> {
+    fn void<A: 'a + Send>(fa: Self::F<A>) -> Self::F<()> {
         fa?;
         Self::pure(())
     }
 }
 
 impl<'a> Pure<'a> for OptionInstance {
-    fn pure<A: 'a>(a: A) -> Self::F<A> {
+    fn pure<A: 'a + Send>(a: A) -> Self::F<A> {
         Some(a)
     }
 }
 
 impl<'a> ApplicativeSeq<'a> for OptionInstance {
-    fn seq<A: 'a, B: 'a>(ff: Self::F<impl 'a + FnOnce(A) -> B>, fa: Self::F<A>) -> Self::F<B> {
+    fn seq<A: 'a + Send, B: 'a + Send>(
+        ff: Self::F<impl 'a + Send + FnOnce(A) -> B>,
+        fa: Self::F<A>,
+    ) -> Self::F<B> {
         Self::pure(ff?(fa?))
     }
 }
 
 impl<'a> ApplicativeLA2<'a> for OptionInstance {
-    fn la2<A: 'a, B: 'a, C: 'a>(
+    fn la2<A: 'a + Send, B: 'a + Send, C: 'a + Send>(
         fa: Self::F<A>,
         fb: Self::F<B>,
-        f: impl 'a + FnOnce(A, B) -> C,
+        f: impl 'a + Send + FnOnce(A, B) -> C,
     ) -> Self::F<C> {
         Self::pure(f(fa?, fb?))
     }
 }
 
 impl<'a> ApplicativeTuple<'a> for OptionInstance {
-    fn tuple<A: 'a, B: 'a>((fa, fb): (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
+    fn tuple<A: 'a + Send, B: 'a + Send>((fa, fb): (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
         Self::pure((fa?, fb?))
     }
 }
@@ -67,23 +73,26 @@ impl<'a> ApplicativeTuple<'a> for OptionInstance {
 impl<'a> ApplicativeSelect<'a> for OptionInstance {}
 
 impl<'a> Applicative<'a> for OptionInstance {
-    fn discard_first<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
+    fn discard_first<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
         fa?;
         fb
     }
 
-    fn discard_second<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
+    fn discard_second<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
         fb?;
         fa
     }
 }
 
 impl<'a> Monad<'a> for OptionInstance {
-    fn bind<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> Self::F<B>) -> Self::F<B> {
+    fn bind<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + FnOnce(A) -> Self::F<B>,
+    ) -> Self::F<B> {
         f(fa?)
     }
 
-    fn iterate<B: 'a>(mut f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
+    fn iterate<B: 'a + Send>(mut f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
         loop {
             match f.next()? {
                 ControlFlow::Continue(next_f) => f = next_f,
@@ -92,13 +101,15 @@ impl<'a> Monad<'a> for OptionInstance {
         }
     }
 
-    fn join<A: 'a>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
+    fn join<A: 'a + Send>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
         ffa?
     }
 }
 
 impl<'a> LocalFunctor<'a> for OptionInstance {
-    fn unstuff<A: 'a, B: 'a>(state: Self::F<ControlFlow<B, A>>) -> ControlFlow<Self::F<B>, A> {
+    fn unstuff<A: 'a + Send, B: 'a + Send>(
+        state: Self::F<ControlFlow<B, A>>,
+    ) -> ControlFlow<Self::F<B>, A> {
         match state {
             Some(ControlFlow::Continue(a)) => ControlFlow::Continue(a),
             Some(ControlFlow::Break(b)) => ControlFlow::Break(Some(b)),
@@ -106,7 +117,7 @@ impl<'a> LocalFunctor<'a> for OptionInstance {
         }
     }
 
-    fn stuff<A: 'a, T: Pure<'a>>(fa: Self::F<T::F<A>>) -> T::F<Self::F<A>> {
+    fn stuff<A: 'a + Send, T: Pure<'a>>(fa: Self::F<T::F<A>>) -> T::F<Self::F<A>> {
         match fa {
             Some(ua) => T::fmap(ua, Some),
             None => T::pure(None),
@@ -115,7 +126,7 @@ impl<'a> LocalFunctor<'a> for OptionInstance {
 }
 
 impl<'a> Fail<'a, ()> for OptionInstance {
-    fn fail<A: 'a>(_e: ()) -> Self::F<A> {
+    fn fail<A: 'a + Send>(_e: ()) -> Self::F<A> {
         None
     }
 }
@@ -127,7 +138,7 @@ mod option_tests {
     use super::OptionInstance as T;
 
     impl<'a> tests::Eqr<'a> for T {
-        fn eqr<A: PartialEq + std::fmt::Debug + 'a>(
+        fn eqr<A: 'a + Send + PartialEq + std::fmt::Debug>(
             name: &'a str,
             left: Self::F<A>,
             right: Self::F<A>,
@@ -137,7 +148,7 @@ mod option_tests {
     }
 
     impl<'a> test_suite::FunctorTestSuite<'a> for T {
-        fn sample<A: 'a, F: FnMut(&'a dyn Fn(A) -> Self::F<A>)>(mut f: F) {
+        fn sample<A: 'a + Send, F: FnMut(&'a (dyn Send + Sync + Fn(A) -> Self::F<A>))>(mut f: F) {
             f(&|_| None);
             f(&|a| Some(a));
         }

src/func/instances/overload.rs

@@ -12,34 +12,37 @@ use crate::func::class_prelude::*;
 
 pub struct OverloadInstance<T, O>(T, O);
 
-pub trait DeriveWeakFunctor {}
+pub trait DeriveWeakFunctor: Send {}
 impl<O: DeriveFunctor> DeriveWeakFunctor for O {}
-pub trait DeriveFunctor {}
+pub trait DeriveFunctor: Send {}
 impl<O: DeriveApplicative> DeriveFunctor for O {}
-pub trait DeriveApplicative {}
+pub trait DeriveApplicative: Send {}
 impl<O: DeriveMonad> DeriveApplicative for O {}
-pub trait DeriveMonad {}
+pub trait DeriveMonad: Send {}
 
 impl<'a, T: WeakFunctor<'a>, O: 'a + DeriveWeakFunctor> WeakFunctor<'a> for OverloadInstance<T, O> {
-    type F<A: 'a> = T::F<A>;
+    type F<A: 'a + Send> = T::F<A>;
 }
 
 impl<'a, T: Functor<'a>, O: 'a + DeriveFunctor> Functor<'a> for OverloadInstance<T, O> {
-    fn fmap<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> B) -> Self::F<B> {
+    fn fmap<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + Send + FnOnce(A) -> B,
+    ) -> Self::F<B> {
         T::fmap(fa, f)
     }
 
-    fn replace<A: 'a, B: 'a>(fa: Self::F<A>, b: B) -> Self::F<B> {
+    fn replace<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, b: B) -> Self::F<B> {
         T::replace(fa, b)
     }
 
-    fn void<A: 'a>(fa: Self::F<A>) -> Self::F<()> {
+    fn void<A: 'a + Send>(fa: Self::F<A>) -> Self::F<()> {
         T::void(fa)
     }
 }
 
 impl<'a, T: Pure<'a>, O: 'a + DeriveApplicative> Pure<'a> for OverloadInstance<T, O> {
-    fn pure<A: 'a>(a: A) -> Self::F<A> {
+    fn pure<A: 'a + Send>(a: A) -> Self::F<A> {
         T::pure(a)
     }
 }
@@ -47,7 +50,10 @@ impl<'a, T: Pure<'a>, O: 'a + DeriveApplicative> Pure<'a> for OverloadInstance<T
 impl<'a, T: ApplicativeSeq<'a>, O: 'a + DeriveApplicative> ApplicativeSeq<'a>
     for OverloadInstance<T, O>
 {
-    fn seq<A: 'a, B: 'a>(ff: Self::F<impl 'a + FnOnce(A) -> B>, fa: Self::F<A>) -> Self::F<B> {
+    fn seq<A: 'a + Send, B: 'a + Send>(
+        ff: Self::F<impl 'a + Send + FnOnce(A) -> B>,
+        fa: Self::F<A>,
+    ) -> Self::F<B> {
         T::seq(ff, fa)
     }
 }
@@ -55,10 +61,10 @@ impl<'a, T: ApplicativeSeq<'a>, O: 'a + DeriveApplicative> ApplicativeSeq<'a>
 impl<'a, T: ApplicativeLA2<'a>, O: 'a + DeriveApplicative> ApplicativeLA2<'a>
     for OverloadInstance<T, O>
 {
-    fn la2<A: 'a, B: 'a, C: 'a>(
+    fn la2<A: 'a + Send, B: 'a + Send, C: 'a + Send>(
         fa: Self::F<A>,
         fb: Self::F<B>,
-        f: impl 'a + FnOnce(A, B) -> C,
+        f: impl 'a + Send + FnOnce(A, B) -> C,
     ) -> Self::F<C> {
         T::la2(fa, fb, f)
     }
@@ -67,7 +73,7 @@ impl<'a, T: ApplicativeLA2<'a>, O: 'a + DeriveApplicative> ApplicativeLA2<'a>
 impl<'a, T: ApplicativeTuple<'a>, O: 'a + DeriveApplicative> ApplicativeTuple<'a>
     for OverloadInstance<T, O>
 {
-    fn tuple<A: 'a, B: 'a>(fab: (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
+    fn tuple<A: 'a + Send, B: 'a + Send>(fab: (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
         T::tuple(fab)
     }
 }
@@ -75,7 +81,10 @@ impl<'a, T: ApplicativeTuple<'a>, O: 'a + DeriveApplicative> ApplicativeTuple<'a
 impl<'a, T: ApplicativeSelect<'a>, O: 'a + DeriveApplicative> ApplicativeSelect<'a>
     for OverloadInstance<T, O>
 {
-    fn select<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> SelectedWrapped<'a, A, B, Self> {
+    fn select<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        fb: Self::F<B>,
+    ) -> SelectedWrapped<'a, A, B, Self> {
         T::select_map(fa, fb, |selected| match selected {
             Selected::A(a, fb) => Selected::A(a, fb),
             Selected::B(fa, b) => Selected::B(fa, b),
@@ -84,11 +93,11 @@ impl<'a, T: ApplicativeSelect<'a>, O: 'a + DeriveApplicative> ApplicativeSelect<
 }
 
 impl<'a, T: Applicative<'a>, O: 'a + DeriveApplicative> Applicative<'a> for OverloadInstance<T, O> {
-    fn discard_first<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
+    fn discard_first<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
         T::discard_first(fa, fb)
     }
 
-    fn discard_second<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
+    fn discard_second<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
         T::discard_second(fa, fb)
     }
 }
@@ -116,25 +125,30 @@ impl<'a, T: Monad<'a>, O: 'a + DeriveMonad, F: Iterative<'a, T = OverloadInstanc
 }
 
 impl<'a, T: Monad<'a>, O: 'a + DeriveMonad> Monad<'a> for OverloadInstance<T, O> {
-    fn bind<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> Self::F<B>) -> Self::F<B> {
+    fn bind<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + Send + FnOnce(A) -> Self::F<B>,
+    ) -> Self::F<B> {
         T::bind(fa, f)
     }
 
-    fn iterate<B: 'a>(f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
+    fn iterate<B: 'a + Send>(f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
         T::iterate(OverloadIterative::new(f))
     }
 
-    fn join<A: 'a>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
+    fn join<A: 'a + Send>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
         T::join(ffa)
     }
 }
 
 pub struct DeriveFail<Ex>(Ex);
 
-impl<Ex> DeriveMonad for DeriveFail<Ex> {}
+impl<Ex: Send> DeriveMonad for DeriveFail<Ex> {}
 
-impl<'a, E: 'a, Ex: 'a, T: MonadFail<'a, Result<E, Ex>>> Fail<'a, E> for EmbedFail<T, Ex> {
-    fn fail<A: 'a>(e: E) -> Self::F<A> {
+impl<'a, E: 'a + Send, Ex: 'a + Send, T: MonadFail<'a, Result<E, Ex>>> Fail<'a, E>
+    for EmbedFail<T, Ex>
+{
+    fn fail<A: 'a + Send>(e: E) -> Self::F<A> {
         T::fail(Ok(e))
     }
 }
@@ -142,19 +156,25 @@ impl<'a, E: 'a, Ex: 'a, T: MonadFail<'a, Result<E, Ex>>> Fail<'a, E> for EmbedFa
 /// Instance of [`MonadFailAny`] for [`EmbedFail`].
 pub struct DeriveFailAny<Ex, Fallible>(Ex, Fallible);
 
-impl<'a, Ex: 'a, Fallible: MonadFailAny<'a>> MonadFailAny<'a> for DeriveFailAny<Ex, Fallible> {
-    type W<E: 'a> = EmbedFail<Fallible::W<Result<E, Ex>>, Ex>;
+impl<'a, Ex: 'a + Send, Fallible: MonadFailAny<'a>> MonadFailAny<'a>
+    for DeriveFailAny<Ex, Fallible>
+{
+    type W<E: 'a + Send> = EmbedFail<Fallible::W<Result<E, Ex>>, Ex>;
 
     type T = Fallible::W<Ex>;
 
-    fn unstuff<A: 'a, E: 'a>(wa: WrapE<'a, A, E, Self>) -> Wrap<'a, Result<A, E>, Self::T> {
+    fn unstuff<A: 'a + Send, E: 'a + Send>(
+        wa: WrapE<'a, A, E, Self>,
+    ) -> Wrap<'a, Result<A, E>, Self::T> {
         Fallible::bind_err(<Self::W<E> as Functor>::fmap(wa, Ok), |err| match err {
             Ok(e) => Fallible::pure(Err(e)),
             Err(ex) => Fallible::fail(ex),
         })
     }
 
-    fn stuff<A: 'a, E: 'a>(fa: Wrap<'a, Result<A, E>, Self::T>) -> WrapE<'a, A, E, Self> {
+    fn stuff<A: 'a + Send, E: 'a + Send>(
+        fa: Wrap<'a, Result<A, E>, Self::T>,
+    ) -> WrapE<'a, A, E, Self> {
         Fallible::bind(fa, |result| match result {
             Ok(Ok(a)) => Fallible::pure(a),
             Ok(Err(e)) => Fallible::fail(Ok(e)),
@@ -162,16 +182,16 @@ impl<'a, Ex: 'a, Fallible: MonadFailAny<'a>> MonadFailAny<'a> for DeriveFailAny<
         })
     }
 
-    fn map_err<A: 'a, E0: 'a, E1: 'a>(
+    fn map_err<A: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, A, E0, Self>,
-        f: impl 'a + FnOnce(E0) -> E1,
+        f: impl 'a + Send + FnOnce(E0) -> E1,
     ) -> WrapE<'a, A, E1, Self> {
         Fallible::map_err(wa, |err| err.map(f))
     }
 
-    fn bind_err<A: 'a, E0: 'a, E1: 'a>(
+    fn bind_err<A: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, A, E0, Self>,
-        f: impl 'a + FnOnce(E0) -> WrapE<'a, A, E1, Self>,
+        f: impl 'a + Send + FnOnce(E0) -> WrapE<'a, A, E1, Self>,
     ) -> WrapE<'a, A, E1, Self> {
         Fallible::bind_err(wa, |err| match err {
             Ok(e0) => f(e0),
@@ -179,9 +199,9 @@ impl<'a, Ex: 'a, Fallible: MonadFailAny<'a>> MonadFailAny<'a> for DeriveFailAny<
         })
     }
 
-    fn bind<A: 'a, B: 'a, E0: 'a, E1: 'a>(
+    fn bind<A: 'a + Send, B: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, A, E0, Self>,
-        f: impl 'a + FnOnce(Result<A, E0>) -> WrapE<'a, B, E1, Self>,
+        f: impl 'a + Send + FnOnce(Result<A, E0>) -> WrapE<'a, B, E1, Self>,
     ) -> WrapE<'a, B, E1, Self> {
         Fallible::bind(wa, |result| match result {
             Ok(a) => f(Ok(a)),
@@ -194,13 +214,13 @@ impl<'a, Ex: 'a, Fallible: MonadFailAny<'a>> MonadFailAny<'a> for DeriveFailAny<
 impl<'a, T: SharedFunctor<'a>, O: 'a + DeriveWeakFunctor> SharedFunctor<'a>
     for OverloadInstance<T, O>
 {
-    type Shared<A: 'a + Clone> = T::Shared<A>;
+    type Shared<A: 'a + Send + Sync + Clone> = T::Shared<A>;
 
-    fn share<A: 'a + Clone>(fa: Self::F<A>) -> Self::Shared<A> {
+    fn share<A: 'a + Send + Sync + Clone>(fa: Self::F<A>) -> Self::Shared<A> {
         T::share(fa)
     }
 
-    fn unshare<A: 'a + Clone>(sa: Self::Shared<A>) -> Self::F<A> {
+    fn unshare<A: 'a + Send + Sync + Clone>(sa: Self::Shared<A>) -> Self::F<A> {
         T::unshare(sa)
     }
 }

src/func/instances/result.rs

@@ -14,77 +14,105 @@
 
 use crate::func::class_prelude::*;
 
-#[derive(SharedFunctorAny)]
-pub struct ResultInstance<E>(E);
+pub struct ResultInstance<E: Send>(E);
 
-impl<E> WeakFunctorAny for ResultInstance<E> {
-    type FAny<'a, A: 'a> = Result<A, E> where Self: 'a;
+impl<E: Send + Sync + Clone> SharedFunctorAny for ResultInstance<E> {
+    type SharedAny<'a, A: 'a + Send + Sync + Clone> = Self::FAny<'a, A>
+    where
+        Self: 'a;
+
+    fn share<'a, A: 'a + Send + Sync + Clone>(fa: Self::FAny<'a, A>) -> Self::SharedAny<'a, A>
+    where
+        Self: 'a,
+    {
+        fa
+    }
+
+    fn unshare<'a, A: 'a + Send + Sync + Clone>(sa: Self::SharedAny<'a, A>) -> Self::FAny<'a, A>
+    where
+        Self: 'a,
+    {
+        sa
+    }
 }
 
-impl<'a, E: 'a> Functor<'a> for ResultInstance<E> {
-    fn fmap<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> B) -> Self::F<B> {
+impl<E: Send> WeakFunctorAny for ResultInstance<E> {
+    type FAny<'a, A: 'a + Send> = Result<A, E> where Self: 'a;
+}
+
+impl<'a, E: 'a + Send> Functor<'a> for ResultInstance<E> {
+    fn fmap<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + Send + FnOnce(A) -> B,
+    ) -> Self::F<B> {
         fa.map(f)
     }
 
-    fn replace<A: 'a, B: 'a>(fa: Self::F<A>, b: B) -> Self::F<B> {
+    fn replace<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, b: B) -> Self::F<B> {
         fa?;
         Self::pure(b)
     }
 
-    fn void<A: 'a>(fa: Self::F<A>) -> Self::F<()> {
+    fn void<A: 'a + Send>(fa: Self::F<A>) -> Self::F<()> {
         fa?;
         Self::pure(())
     }
 }
 
-impl<'a, E: 'a> Pure<'a> for ResultInstance<E> {
-    fn pure<A: 'a>(a: A) -> Self::F<A> {
+impl<'a, E: 'a + Send> Pure<'a> for ResultInstance<E> {
+    fn pure<A: 'a + Send>(a: A) -> Self::F<A> {
         Ok(a)
     }
 }
 
-impl<'a, E: 'a> ApplicativeSeq<'a> for ResultInstance<E> {
-    fn seq<A: 'a, B: 'a>(ff: Self::F<impl 'a + FnOnce(A) -> B>, fa: Self::F<A>) -> Self::F<B> {
+impl<'a, E: 'a + Send> ApplicativeSeq<'a> for ResultInstance<E> {
+    fn seq<A: 'a + Send, B: 'a + Send>(
+        ff: Self::F<impl 'a + Send + FnOnce(A) -> B>,
+        fa: Self::F<A>,
+    ) -> Self::F<B> {
         Self::pure(ff?(fa?))
     }
 }
 
-impl<'a, E: 'a> ApplicativeLA2<'a> for ResultInstance<E> {
-    fn la2<A: 'a, B: 'a, C: 'a>(
+impl<'a, E: 'a + Send> ApplicativeLA2<'a> for ResultInstance<E> {
+    fn la2<A: 'a + Send, B: 'a + Send, C: 'a + Send>(
         fa: Self::F<A>,
         fb: Self::F<B>,
-        f: impl 'a + FnOnce(A, B) -> C,
+        f: impl 'a + Send + FnOnce(A, B) -> C,
     ) -> Self::F<C> {
         Self::pure(f(fa?, fb?))
     }
 }
 
-impl<'a, E: 'a> ApplicativeTuple<'a> for ResultInstance<E> {
-    fn tuple<A: 'a, B: 'a>((fa, fb): (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
+impl<'a, E: 'a + Send> ApplicativeTuple<'a> for ResultInstance<E> {
+    fn tuple<A: 'a + Send, B: 'a + Send>((fa, fb): (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
         Self::pure((fa?, fb?))
     }
 }
 
-impl<'a, E: 'a> ApplicativeSelect<'a> for ResultInstance<E> {}
+impl<'a, E: 'a + Send> ApplicativeSelect<'a> for ResultInstance<E> {}
 
-impl<'a, E: 'a> Applicative<'a> for ResultInstance<E> {
-    fn discard_first<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
+impl<'a, E: 'a + Send> Applicative<'a> for ResultInstance<E> {
+    fn discard_first<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
         fa?;
         fb
     }
 
-    fn discard_second<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
+    fn discard_second<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
         fb?;
         fa
     }
 }
 
-impl<'a, E: 'a> Monad<'a> for ResultInstance<E> {
-    fn bind<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> Self::F<B>) -> Self::F<B> {
+impl<'a, E: 'a + Send> Monad<'a> for ResultInstance<E> {
+    fn bind<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + FnOnce(A) -> Self::F<B>,
+    ) -> Self::F<B> {
         f(fa?)
     }
 
-    fn iterate<B: 'a>(mut f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
+    fn iterate<B: 'a + Send>(mut f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
         loop {
             match f.next()? {
                 ControlFlow::Continue(next_f) => f = next_f,
@@ -93,13 +121,15 @@ impl<'a, E: 'a> Monad<'a> for ResultInstance<E> {
         }
     }
 
-    fn join<A: 'a>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
+    fn join<A: 'a + Send>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
         ffa?
     }
 }
 
-impl<'a, E: 'a> LocalFunctor<'a> for ResultInstance<E> {
-    fn unstuff<A: 'a, B: 'a>(state: Self::F<ControlFlow<B, A>>) -> ControlFlow<Self::F<B>, A> {
+impl<'a, E: 'a + Send> LocalFunctor<'a> for ResultInstance<E> {
+    fn unstuff<A: 'a + Send, B: 'a + Send>(
+        state: Self::F<ControlFlow<B, A>>,
+    ) -> ControlFlow<Self::F<B>, A> {
         match state {
             Ok(ControlFlow::Continue(a)) => ControlFlow::Continue(a),
             Ok(ControlFlow::Break(b)) => ControlFlow::Break(Ok(b)),
@@ -107,7 +137,7 @@ impl<'a, E: 'a> LocalFunctor<'a> for ResultInstance<E> {
         }
     }
 
-    fn stuff<A: 'a, T: Pure<'a>>(fa: Self::F<T::F<A>>) -> T::F<Self::F<A>> {
+    fn stuff<A: 'a + Send, T: Pure<'a>>(fa: Self::F<T::F<A>>) -> T::F<Self::F<A>> {
         match fa {
             Ok(ua) => T::fmap(ua, Ok),
             Err(e) => T::pure(Err(e)),
@@ -115,20 +145,20 @@ impl<'a, E: 'a> LocalFunctor<'a> for ResultInstance<E> {
     }
 }
 
-impl<'a, E: 'a> Fail<'a, E> for ResultInstance<E> {
-    fn fail<A: 'a>(e: E) -> Self::F<A> {
+impl<'a, E: 'a + Send> Fail<'a, E> for ResultInstance<E> {
+    fn fail<A: 'a + Send>(e: E) -> Self::F<A> {
         Err(e)
     }
 }
 
 pub struct ResultFailAny;
 
-trait ResultExt<'a, A: 'a, E0: 'a>: 'a {
-    fn bind_err<E1: 'a>(self, f: impl 'a + FnOnce(E0) -> Result<A, E1>) -> Result<A, E1>;
+trait ResultExt<'a, A: 'a + Send, E0: 'a + Send>: 'a {
+    fn bind_err<E1: 'a + Send>(self, f: impl 'a + FnOnce(E0) -> Result<A, E1>) -> Result<A, E1>;
 }
 
-impl<'a, A: 'a, E0: 'a> ResultExt<'a, A, E0> for Result<A, E0> {
-    fn bind_err<E1: 'a>(self, f: impl 'a + FnOnce(E0) -> Result<A, E1>) -> Result<A, E1> {
+impl<'a, A: 'a + Send, E0: 'a + Send> ResultExt<'a, A, E0> for Result<A, E0> {
+    fn bind_err<E1: 'a + Send>(self, f: impl 'a + FnOnce(E0) -> Result<A, E1>) -> Result<A, E1> {
         match self {
             Ok(a) => Ok(a),
             Err(e) => f(e),
@@ -137,40 +167,44 @@ impl<'a, A: 'a, E0: 'a> ResultExt<'a, A, E0> for Result<A, E0> {
 }
 
 impl<'a> MonadFailAny<'a> for ResultFailAny {
-    type W<E: 'a> = ResultInstance<E>;
+    type W<E: 'a + Send> = ResultInstance<E>;
 
     type T = instances::solo::SoloInstance;
 
-    fn unstuff<A: 'a, E: 'a>(wa: WrapE<'a, A, E, Self>) -> Wrap<'a, Result<A, E>, Self::T> {
+    fn unstuff<A: 'a + Send, E: 'a + Send>(
+        wa: WrapE<'a, A, E, Self>,
+    ) -> Wrap<'a, Result<A, E>, Self::T> {
         wa
     }
 
-    fn stuff<A: 'a, E: 'a>(fa: Wrap<'a, Result<A, E>, Self::T>) -> WrapE<'a, A, E, Self> {
+    fn stuff<A: 'a + Send, E: 'a + Send>(
+        fa: Wrap<'a, Result<A, E>, Self::T>,
+    ) -> WrapE<'a, A, E, Self> {
         fa
     }
 
-    fn map_err<A: 'a, E0: 'a, E1: 'a>(
+    fn map_err<A: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, A, E0, Self>,
         f: impl 'a + FnOnce(E0) -> E1,
     ) -> WrapE<'a, A, E1, Self> {
         wa.map_err(f)
     }
 
-    fn bind_err<A: 'a, E0: 'a, E1: 'a>(
+    fn bind_err<A: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, A, E0, Self>,
         f: impl 'a + FnOnce(E0) -> WrapE<'a, A, E1, Self>,
     ) -> WrapE<'a, A, E1, Self> {
         wa.bind_err(f)
     }
 
-    fn bind<A: 'a, B: 'a, E0: 'a, E1: 'a>(
+    fn bind<A: 'a + Send, B: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, A, E0, Self>,
         f: impl 'a + FnOnce(Result<A, E0>) -> WrapE<'a, B, E1, Self>,
     ) -> WrapE<'a, B, E1, Self> {
         f(wa)
     }
 
-    fn rotate_out<A: 'a, E0: 'a, E1: 'a>(
+    fn rotate_out<A: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, Result<A, E1>, E0, Self>,
     ) -> WrapE<'a, A, Result<E1, E0>, Self> {
         match wa {
@@ -184,28 +218,32 @@ impl<'a> MonadFailAny<'a> for ResultFailAny {
 pub struct ResultFailOver<T>(T);
 
 impl<'a, T: Monad<'a>> MonadFailAny<'a> for ResultFailOver<T> {
-    type W<E: 'a> = super::composition::CompositionInstance<T, ResultInstance<E>>;
+    type W<E: 'a + Send> = super::composition::CompositionInstance<T, ResultInstance<E>>;
 
     type T = T;
 
-    fn unstuff<A: 'a, E: 'a>(wa: WrapE<'a, A, E, Self>) -> Wrap<'a, Result<A, E>, Self::T> {
+    fn unstuff<A: 'a + Send, E: 'a + Send>(
+        wa: WrapE<'a, A, E, Self>,
+    ) -> Wrap<'a, Result<A, E>, Self::T> {
         wa
     }
 
-    fn stuff<A: 'a, E: 'a>(fa: Wrap<'a, Result<A, E>, Self::T>) -> WrapE<'a, A, E, Self> {
+    fn stuff<A: 'a + Send, E: 'a + Send>(
+        fa: Wrap<'a, Result<A, E>, Self::T>,
+    ) -> WrapE<'a, A, E, Self> {
         fa
     }
 
-    fn map_err<A: 'a, E0: 'a, E1: 'a>(
+    fn map_err<A: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, A, E0, Self>,
-        f: impl 'a + FnOnce(E0) -> E1,
+        f: impl 'a + Send + FnOnce(E0) -> E1,
     ) -> WrapE<'a, A, E1, Self> {
         T::fmap(wa, |a| a.map_err(f))
     }
 
-    fn bind_err<A: 'a, E0: 'a, E1: 'a>(
+    fn bind_err<A: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, A, E0, Self>,
-        f: impl 'a + FnOnce(E0) -> WrapE<'a, A, E1, Self>,
+        f: impl 'a + Send + FnOnce(E0) -> WrapE<'a, A, E1, Self>,
     ) -> WrapE<'a, A, E1, Self> {
         T::bind(wa, |a| match a {
             Ok(a) => T::pure(Ok(a)),
@@ -213,14 +251,14 @@ impl<'a, T: Monad<'a>> MonadFailAny<'a> for ResultFailOver<T> {
         })
     }
 
-    fn bind<A: 'a, B: 'a, E0: 'a, E1: 'a>(
+    fn bind<A: 'a + Send, B: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, A, E0, Self>,
-        f: impl 'a + FnOnce(Result<A, E0>) -> WrapE<'a, B, E1, Self>,
+        f: impl 'a + Send + FnOnce(Result<A, E0>) -> WrapE<'a, B, E1, Self>,
     ) -> WrapE<'a, B, E1, Self> {
         T::bind(wa, f)
     }
 
-    fn rotate_out<A: 'a, E0: 'a, E1: 'a>(
+    fn rotate_out<A: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, Result<A, E1>, E0, Self>,
     ) -> WrapE<'a, A, Result<E1, E0>, Self> {
         T::fmap(wa, <ResultFailAny as MonadFailAny>::rotate_out)

src/func/instances/solo.rs

@@ -14,48 +14,51 @@ use crate::func::class_prelude::*;
 pub struct SoloInstance;
 
 impl WeakFunctorAny for SoloInstance {
-    type FAny<'a, A: 'a> = A;
+    type FAny<'a, A: 'a + Send> = A;
 }
 
 impl<'a> Functor<'a> for SoloInstance {
-    fn fmap<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> B) -> Self::F<B> {
+    fn fmap<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> B) -> Self::F<B> {
         f(fa)
     }
 
-    fn replace<A: 'a, B: 'a>(fa: Self::F<A>, b: B) -> Self::F<B> {
+    fn replace<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, b: B) -> Self::F<B> {
         drop(fa);
         b
     }
 
-    fn void<A: 'a>(fa: Self::F<A>) -> Self::F<()> {
+    fn void<A: 'a + Send>(fa: Self::F<A>) -> Self::F<()> {
         drop(fa);
     }
 }
 
 impl<'a> Pure<'a> for SoloInstance {
-    fn pure<A: 'a>(a: A) -> Self::F<A> {
+    fn pure<A: 'a + Send>(a: A) -> Self::F<A> {
         a
     }
 }
 
 impl<'a> ApplicativeSeq<'a> for SoloInstance {
-    fn seq<A: 'a, B: 'a>(ff: Self::F<impl 'a + FnOnce(A) -> B>, fa: Self::F<A>) -> Self::F<B> {
+    fn seq<A: 'a + Send, B: 'a + Send>(
+        ff: Self::F<impl 'a + Send + FnOnce(A) -> B>,
+        fa: Self::F<A>,
+    ) -> Self::F<B> {
         ff(fa)
     }
 }
 
 impl<'a> ApplicativeLA2<'a> for SoloInstance {
-    fn la2<A: 'a, B: 'a, C: 'a>(
+    fn la2<A: 'a + Send, B: 'a + Send, C: 'a + Send>(
         fa: Self::F<A>,
         fb: Self::F<B>,
-        f: impl 'a + FnOnce(A, B) -> C,
+        f: impl 'a + Send + FnOnce(A, B) -> C,
     ) -> Self::F<C> {
         f(fa, fb)
     }
 }
 
 impl<'a> ApplicativeTuple<'a> for SoloInstance {
-    fn tuple<A: 'a, B: 'a>((fa, fb): (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
+    fn tuple<A: 'a + Send, B: 'a + Send>((fa, fb): (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
         (fa, fb)
     }
 }
@@ -63,23 +66,26 @@ impl<'a> ApplicativeTuple<'a> for SoloInstance {
 impl<'a> ApplicativeSelect<'a> for SoloInstance {}
 
 impl<'a> Applicative<'a> for SoloInstance {
-    fn discard_first<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
+    fn discard_first<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
         drop(fa);
         fb
     }
 
-    fn discard_second<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
+    fn discard_second<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
         drop(fb);
         fa
     }
 }
 
 impl<'a> Monad<'a> for SoloInstance {
-    fn bind<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> Self::F<B>) -> Self::F<B> {
+    fn bind<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + FnOnce(A) -> Self::F<B>,
+    ) -> Self::F<B> {
         f(fa)
     }
 
-    fn iterate<B: 'a>(mut f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
+    fn iterate<B: 'a + Send>(mut f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
         loop {
             match f.next() {
                 ControlFlow::Continue(next_f) => f = next_f,
@@ -88,23 +94,25 @@ impl<'a> Monad<'a> for SoloInstance {
         }
     }
 
-    fn join<A: 'a>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
+    fn join<A: 'a + Send>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
         ffa
     }
 }
 
 impl<'a> LocalFunctor<'a> for SoloInstance {
-    fn unstuff<A: 'a, B: 'a>(state: Self::F<ControlFlow<B, A>>) -> ControlFlow<Self::F<B>, A> {
+    fn unstuff<A: 'a + Send, B: 'a + Send>(
+        state: Self::F<ControlFlow<B, A>>,
+    ) -> ControlFlow<Self::F<B>, A> {
         state
     }
 
-    fn stuff<A: 'a, T: Pure<'a>>(fa: Self::F<T::F<A>>) -> T::F<Self::F<A>> {
+    fn stuff<A: 'a + Send, T: Pure<'a>>(fa: Self::F<T::F<A>>) -> T::F<Self::F<A>> {
         fa
     }
 }
 
 impl<'a> Fail<'a, std::convert::Infallible> for SoloInstance {
-    fn fail<A: 'a>(e: std::convert::Infallible) -> Self::F<A> {
+    fn fail<A: 'a + Send>(e: std::convert::Infallible) -> Self::F<A> {
         match e {}
     }
 }

src/func/instances/stackless.rs

@@ -6,7 +6,7 @@
 //! [`lazy`]: super::lazy
 
 use std::marker::PhantomData;
-use std::{cell::Cell, rc::Rc};
+use std::{cell::Cell, sync::Arc};
 
 use crate::func::class_prelude::*;
 use crate::func::derivations::{ApplicativeLA2ViaSeq, ApplicativeTupleViaLA2};
@@ -83,14 +83,14 @@ impl<'a> EvalTree<'a> {
     }
 }
 
-trait IntoOet<A> {
+trait IntoOet<A>: Send {
     fn into_oet<'t>(self: Box<Self>, f: Box<dyn 't + FnOnce(A)>) -> Oet<'t>
     where
         Self: 't,
         A: 't;
 }
 
-impl<'a, A: 'a, B: 'a, F: 'a + FnOnce(A) -> Stackless<'a, B>> IntoOet<B>
+impl<'a, A: 'a + Send, B: 'a + Send, F: 'a + Send + FnOnce(A) -> Stackless<'a, B>> IntoOet<B>
     for Wrapper<(&'a (), B), (Stackless<'a, A>, F)>
 {
     fn into_oet<'t>(self: Box<Self>, f: Box<dyn 't + FnOnce(B)>) -> Oet<'t>
@@ -98,7 +98,7 @@ impl<'a, A: 'a, B: 'a, F: 'a + FnOnce(A) -> Stackless<'a, B>> IntoOet<B>
         Self: 't,
         A: 't,
     {
-        let cell_l = Rc::new(Cell::new(None));
+        let cell_l = Arc::new(Cell::new(None));
         let cell_r = cell_l.clone();
         let (sstackless, sf) = self.0;
         Some(EvalTree::Composite(
@@ -111,7 +111,7 @@ impl<'a, A: 'a, B: 'a, F: 'a + FnOnce(A) -> Stackless<'a, B>> IntoOet<B>
     }
 }
 
-impl<'a, A: 'a, B: 'a, F: 'a + FnOnce(A) -> B> IntoOet<B>
+impl<'a, A: 'a + Send, B: 'a + Send, F: 'a + Send + FnOnce(A) -> B> IntoOet<B>
     for Wrapper<(&'a (), B, ()), (Stackless<'a, A>, F)>
 {
     fn into_oet<'t>(self: Box<Self>, f: Box<dyn 't + FnOnce(B)>) -> Oet<'t>
@@ -119,7 +119,7 @@ impl<'a, A: 'a, B: 'a, F: 'a + FnOnce(A) -> B> IntoOet<B>
         Self: 't,
         A: 't,
     {
-        let cell_l = Rc::new(Cell::new(None));
+        let cell_l = Arc::new(Cell::new(None));
         let cell_r = cell_l.clone();
         let (sstackless, sf) = self.0;
         Some(EvalTree::Composite(
@@ -135,7 +135,7 @@ impl<'a, A: 'a, B: 'a, F: 'a + FnOnce(A) -> B> IntoOet<B>
     }
 }
 
-impl<A> IntoOet<A> for Wrapper<(), A> {
+impl<A: Send> IntoOet<A> for Wrapper<(), A> {
     fn into_oet<'t>(self: Box<Self>, f: Box<dyn 't + FnOnce(A)>) -> Oet<'t>
     where
         Self: 't,
@@ -152,39 +152,42 @@ type StackessDyn<'a, A> = dyn 'a + IntoOet<A>;
 
 pub struct Stackless<'a, A: 'a>(Box<StackessDyn<'a, A>>);
 
-fn set_cell<A>(cell: Rc<Cell<Option<A>>>, a: A) {
+fn set_cell<A>(cell: Arc<Cell<Option<A>>>, a: A) {
     if cell.replace(Some(a)).is_some() {
         panic!("MITM overwritten")
     }
 }
 
-fn get_cell<A>(cell: Rc<Cell<Option<A>>>) -> A {
+fn get_cell<A>(cell: Arc<Cell<Option<A>>>) -> A {
     match cell.replace(None) {
         Some(val) => val,
         None => panic!("MITM not set"),
     }
 }
 
-impl<'a, A: 'a> Stackless<'a, A> {
+impl<'a, A: 'a + Send> Stackless<'a, A> {
     fn call(self, f: impl 'a + FnOnce(A)) -> Oet<'a> {
         self.0.into_oet(Box::new(f))
     }
 
     /// Method-like equivalent of [`Monad::bind`],
     /// the preferred way to chain [`Stackless<A>`] and `FnOnce(A) -> Stackless<B>` into [`Stackless<B>`].
-    pub fn bind<B: 'a>(self, f: impl 'a + FnOnce(A) -> Stackless<'a, B>) -> Stackless<'a, B> {
+    pub fn bind<B: 'a + Send>(
+        self,
+        f: impl 'a + Send + FnOnce(A) -> Stackless<'a, B>,
+    ) -> Stackless<'a, B> {
         Stackless(Box::new(Wrapper((self, f), PhantomData)))
     }
 
     /// Method-like equivalent of [`Functor::fmap`].
-    pub fn map<B: 'a>(self, f: impl 'a + FnOnce(A) -> B) -> Stackless<'a, B> {
+    pub fn map<B: 'a + Send>(self, f: impl 'a + Send + FnOnce(A) -> B) -> Stackless<'a, B> {
         Stackless(Box::new(Wrapper((self, f), PhantomData)))
     }
 
     /// Evaluate. Process is loop-like on the inside
     /// with the least amount of recursion the current model allows to use.
     pub fn evaluate(self) -> A {
-        let ocell = Rc::new(Cell::new(None));
+        let ocell = Arc::new(Cell::new(None));
         let icell = ocell.clone();
         let mut eval = self.call(|a| set_cell(icell, a));
         while let Some(tree) = eval {
@@ -194,7 +197,7 @@ impl<'a, A: 'a> Stackless<'a, A> {
     }
 }
 
-impl<'a, A: 'a> From<A> for Stackless<'a, A> {
+impl<'a, A: 'a + Send> From<A> for Stackless<'a, A> {
     fn from(value: A) -> Self {
         Stackless(Box::new(Wrapper(value, PhantomData)))
     }
@@ -203,39 +206,45 @@ impl<'a, A: 'a> From<A> for Stackless<'a, A> {
 pub struct StacklessInstance;
 
 impl WeakFunctorAny for StacklessInstance {
-    type FAny<'a, A: 'a> = Stackless<'a, A>;
+    type FAny<'a, A: 'a + Send> = Stackless<'a, A>;
 }
 
 impl<'a> Functor<'a> for StacklessInstance {
-    fn fmap<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> B) -> Self::F<B> {
+    fn fmap<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + Send + FnOnce(A) -> B,
+    ) -> Self::F<B> {
         fa.map(f)
     }
 }
 
 impl<'a> Pure<'a> for StacklessInstance {
-    fn pure<A: 'a>(a: A) -> Self::F<A> {
+    fn pure<A: 'a + Send>(a: A) -> Self::F<A> {
         Stackless::from(a)
     }
 }
 
 impl<'a> ApplicativeSeq<'a> for StacklessInstance {
-    fn seq<A: 'a, B: 'a>(ff: Self::F<impl 'a + FnOnce(A) -> B>, fa: Self::F<A>) -> Self::F<B> {
+    fn seq<A: 'a + Send, B: 'a + Send>(
+        ff: Self::F<impl 'a + Send + FnOnce(A) -> B>,
+        fa: Self::F<A>,
+    ) -> Self::F<B> {
         ff.bind(|f| fa.map(f))
     }
 }
 
 impl<'a> ApplicativeLA2<'a> for StacklessInstance {
-    fn la2<A: 'a, B: 'a, C: 'a>(
+    fn la2<A: 'a + Send, B: 'a + Send, C: 'a + Send>(
         fa: Self::F<A>,
         fb: Self::F<B>,
-        f: impl 'a + FnOnce(A, B) -> C,
+        f: impl 'a + Send + FnOnce(A, B) -> C,
     ) -> Self::F<C> {
         Self::_la2_via_seq(f, fa, fb)
     }
 }
 
 impl<'a> ApplicativeTuple<'a> for StacklessInstance {
-    fn tuple<A: 'a, B: 'a>((fa, fb): (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
+    fn tuple<A: 'a + Send, B: 'a + Send>((fa, fb): (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
         Self::_tuple_via_la2((fa, fb))
     }
 }
@@ -245,11 +254,14 @@ impl<'a> ApplicativeSelect<'a> for StacklessInstance {}
 impl<'a> Applicative<'a> for StacklessInstance {}
 
 impl<'a> Monad<'a> for StacklessInstance {
-    fn bind<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> Self::F<B>) -> Self::F<B> {
+    fn bind<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + Send + FnOnce(A) -> Self::F<B>,
+    ) -> Self::F<B> {
         fa.bind(f)
     }
 
-    fn iterate<B: 'a>(f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
+    fn iterate<B: 'a + Send>(f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
         Self::pure(()).bind(move |_| {
             f.next().bind(|state| match state {
                 ControlFlow::Continue(next_f) => Self::iterate(next_f),
@@ -266,7 +278,7 @@ mod stackless_test {
     use super::StacklessInstance as T;
 
     impl<'a> tests::Eqr<'a> for T {
-        fn eqr<A: PartialEq + std::fmt::Debug + 'a>(
+        fn eqr<A: 'a + Send + PartialEq + std::fmt::Debug>(
             name: &'a str,
             left: Self::F<A>,
             right: Self::F<A>,
@@ -276,7 +288,7 @@ mod stackless_test {
     }
 
     impl<'a> test_suite::FunctorTestSuite<'a> for T {
-        fn sample<A: 'a, F: FnMut(&'a dyn Fn(A) -> Self::F<A>)>(mut f: F) {
+        fn sample<A: 'a + Send, F: FnMut(&'a (dyn Send + Sync + Fn(A) -> Self::F<A>))>(mut f: F) {
             f(&|a| a.into());
         }
     }

src/func/instances/tryfuture.rs

@@ -19,16 +19,19 @@ use crate::func::class_prelude::*;
 
 pub struct TryFutureInstance<E>(E);
 
-impl<E> WeakFunctorAny for TryFutureInstance<E> {
-    type FAny<'a, A: 'a> = Pin<Box<dyn 'a + Future<Output = Result<A, E>>>> where Self: 'a;
+impl<E: Send> WeakFunctorAny for TryFutureInstance<E> {
+    type FAny<'a, A: 'a + Send> = Pin<Box<dyn 'a + Send + Future<Output = Result<A, E>>>> where Self: 'a;
 }
 
-impl<'a, E: 'a> Functor<'a> for TryFutureInstance<E> {
-    fn fmap<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> B) -> Self::F<B> {
+impl<'a, E: 'a + Send> Functor<'a> for TryFutureInstance<E> {
+    fn fmap<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + Send + FnOnce(A) -> B,
+    ) -> Self::F<B> {
         Box::pin(async { Ok(f(fa.await?)) })
     }
 
-    fn replace<A: 'a, B: 'a>(fa: Self::F<A>, b: B) -> Self::F<B> {
+    fn replace<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, b: B) -> Self::F<B> {
         Box::pin(async {
             fa.await?;
             Ok(b)
@@ -36,14 +39,17 @@ impl<'a, E: 'a> Functor<'a> for TryFutureInstance<E> {
     }
 }
 
-impl<'a, E: 'a> Pure<'a> for TryFutureInstance<E> {
-    fn pure<A: 'a>(a: A) -> Self::F<A> {
+impl<'a, E: 'a + Send> Pure<'a> for TryFutureInstance<E> {
+    fn pure<A: 'a + Send>(a: A) -> Self::F<A> {
         Box::pin(async { Ok(a) })
     }
 }
 
-impl<'a, E: 'a> ApplicativeSeq<'a> for TryFutureInstance<E> {
-    fn seq<A: 'a, B: 'a>(ff: Self::F<impl 'a + FnOnce(A) -> B>, fa: Self::F<A>) -> Self::F<B> {
+impl<'a, E: 'a + Send> ApplicativeSeq<'a> for TryFutureInstance<E> {
+    fn seq<A: 'a + Send, B: 'a + Send>(
+        ff: Self::F<impl 'a + Send + FnOnce(A) -> B>,
+        fa: Self::F<A>,
+    ) -> Self::F<B> {
         Box::pin(async {
             let (f, a) = try_join!(ff, fa)?;
             Ok(f(a))
@@ -51,11 +57,11 @@ impl<'a, E: 'a> ApplicativeSeq<'a> for TryFutureInstance<E> {
     }
 }
 
-impl<'a, E: 'a> ApplicativeLA2<'a> for TryFutureInstance<E> {
-    fn la2<A: 'a, B: 'a, C: 'a>(
+impl<'a, E: 'a + Send> ApplicativeLA2<'a> for TryFutureInstance<E> {
+    fn la2<A: 'a + Send, B: 'a + Send, C: 'a + Send>(
         fa: Self::F<A>,
         fb: Self::F<B>,
-        f: impl 'a + FnOnce(A, B) -> C,
+        f: impl 'a + Send + FnOnce(A, B) -> C,
     ) -> Self::F<C> {
         Box::pin(async {
             let (a, b) = try_join!(fa, fb)?;
@@ -64,14 +70,17 @@ impl<'a, E: 'a> ApplicativeLA2<'a> for TryFutureInstance<E> {
     }
 }
 
-impl<'a, E: 'a> ApplicativeTuple<'a> for TryFutureInstance<E> {
-    fn tuple<A: 'a, B: 'a>((fa, fb): (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
+impl<'a, E: 'a + Send> ApplicativeTuple<'a> for TryFutureInstance<E> {
+    fn tuple<A: 'a + Send, B: 'a + Send>((fa, fb): (Self::F<A>, Self::F<B>)) -> Self::F<(A, B)> {
         Box::pin(async { try_join!(fa, fb) })
     }
 }
 
-impl<'a, E: 'a> ApplicativeSelect<'a> for TryFutureInstance<E> {
-    fn select<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> SelectedWrapped<'a, A, B, Self> {
+impl<'a, E: 'a + Send> ApplicativeSelect<'a> for TryFutureInstance<E> {
+    fn select<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        fb: Self::F<B>,
+    ) -> SelectedWrapped<'a, A, B, Self> {
         Box::pin(async {
             match try_select(fa, fb).await {
                 Ok(Either::Left((a, fb))) => Ok(Selected::A(a, fb)),
@@ -83,22 +92,25 @@ impl<'a, E: 'a> ApplicativeSelect<'a> for TryFutureInstance<E> {
     }
 }
 
-impl<'a, E: 'a> Applicative<'a> for TryFutureInstance<E> {
-    fn discard_first<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
+impl<'a, E: 'a + Send> Applicative<'a> for TryFutureInstance<E> {
+    fn discard_first<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<B> {
         Box::pin(async { Ok(try_join!(fa, fb)?.1) })
     }
 
-    fn discard_second<A: 'a, B: 'a>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
+    fn discard_second<A: 'a + Send, B: 'a + Send>(fa: Self::F<A>, fb: Self::F<B>) -> Self::F<A> {
         Box::pin(async { Ok(try_join!(fa, fb)?.0) })
     }
 }
 
-impl<'a, E: 'a> Monad<'a> for TryFutureInstance<E> {
-    fn bind<A: 'a, B: 'a>(fa: Self::F<A>, f: impl 'a + FnOnce(A) -> Self::F<B>) -> Self::F<B> {
+impl<'a, E: 'a + Send> Monad<'a> for TryFutureInstance<E> {
+    fn bind<A: 'a + Send, B: 'a + Send>(
+        fa: Self::F<A>,
+        f: impl 'a + Send + FnOnce(A) -> Self::F<B>,
+    ) -> Self::F<B> {
         Box::pin(async { f(fa.await?).await })
     }
 
-    fn iterate<B: 'a>(mut f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
+    fn iterate<B: 'a + Send>(mut f: impl Iterative<'a, T = Self, B = B>) -> Self::F<B> {
         Box::pin(async move {
             loop {
                 match f.next().await? {
@@ -109,25 +121,26 @@ impl<'a, E: 'a> Monad<'a> for TryFutureInstance<E> {
         })
     }
 
-    fn join<A: 'a>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
+    fn join<A: 'a + Send>(ffa: Self::F<Self::F<A>>) -> Self::F<A> {
         Box::pin(async { ffa.await?.await })
     }
 }
 
-impl<'a, E: 'a + Clone> SharedFunctor<'a> for TryFutureInstance<E> {
-    type Shared<A: 'a + Clone> = Shared<Pin<Box<dyn 'a + Future<Output = Result<A, E>>>>>;
+impl<'a, E: 'a + Send + Sync + Clone> SharedFunctor<'a> for TryFutureInstance<E> {
+    type Shared<A: 'a + Send + Sync + Clone> =
+        Shared<Pin<Box<dyn 'a + Send + Future<Output = Result<A, E>>>>>;
 
-    fn share<A: 'a + Clone>(fa: Self::F<A>) -> Self::Shared<A> {
+    fn share<A: 'a + Send + Sync + Clone>(fa: Self::F<A>) -> Self::Shared<A> {
         fa.shared()
     }
 
-    fn unshare<A: 'a + Clone>(sa: Self::Shared<A>) -> Self::F<A> {
+    fn unshare<A: 'a + Send + Sync + Clone>(sa: Self::Shared<A>) -> Self::F<A> {
         Box::pin(sa)
     }
 }
 
-impl<'a, E: 'a> Fail<'a, E> for TryFutureInstance<E> {
-    fn fail<A: 'a>(e: E) -> Self::F<A> {
+impl<'a, E: 'a + Send> Fail<'a, E> for TryFutureInstance<E> {
+    fn fail<A: 'a + Send>(e: E) -> Self::F<A> {
         Box::pin(async { Err(e) })
     }
 }
@@ -135,28 +148,32 @@ impl<'a, E: 'a> Fail<'a, E> for TryFutureInstance<E> {
 pub struct FutureFailAny;
 
 impl<'a> MonadFailAny<'a> for FutureFailAny {
-    type W<E: 'a> = TryFutureInstance<E>;
+    type W<E: 'a + Send> = TryFutureInstance<E>;
 
     type T = instances::future::FutureInstance;
 
-    fn unstuff<A: 'a, E: 'a>(wa: WrapE<'a, A, E, Self>) -> Wrap<'a, Result<A, E>, Self::T> {
+    fn unstuff<A: 'a + Send, E: 'a + Send>(
+        wa: WrapE<'a, A, E, Self>,
+    ) -> Wrap<'a, Result<A, E>, Self::T> {
         wa
     }
 
-    fn stuff<A: 'a, E: 'a>(fa: Wrap<'a, Result<A, E>, Self::T>) -> WrapE<'a, A, E, Self> {
+    fn stuff<A: 'a + Send, E: 'a + Send>(
+        fa: Wrap<'a, Result<A, E>, Self::T>,
+    ) -> WrapE<'a, A, E, Self> {
         fa
     }
 
-    fn map_err<A: 'a, E0: 'a, E1: 'a>(
+    fn map_err<A: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, A, E0, Self>,
-        f: impl 'a + FnOnce(E0) -> E1,
+        f: impl 'a + Send + FnOnce(E0) -> E1,
     ) -> WrapE<'a, A, E1, Self> {
         Box::pin(async { wa.await.map_err(f) })
     }
 
-    fn bind_err<A: 'a, E0: 'a, E1: 'a>(
+    fn bind_err<A: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, A, E0, Self>,
-        f: impl 'a + FnOnce(E0) -> WrapE<'a, A, E1, Self>,
+        f: impl 'a + Send + FnOnce(E0) -> WrapE<'a, A, E1, Self>,
     ) -> WrapE<'a, A, E1, Self> {
         Box::pin(async {
             match wa.await {
@@ -166,14 +183,14 @@ impl<'a> MonadFailAny<'a> for FutureFailAny {
         })
     }
 
-    fn bind<A: 'a, B: 'a, E0: 'a, E1: 'a>(
+    fn bind<A: 'a + Send, B: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, A, E0, Self>,
-        f: impl 'a + FnOnce(Result<A, E0>) -> WrapE<'a, B, E1, Self>,
+        f: impl 'a + Send + FnOnce(Result<A, E0>) -> WrapE<'a, B, E1, Self>,
     ) -> WrapE<'a, B, E1, Self> {
         Box::pin(async { f(wa.await).await })
     }
 
-    fn rotate_out<A: 'a, E0: 'a, E1: 'a>(
+    fn rotate_out<A: 'a + Send, E0: 'a + Send, E1: 'a + Send>(
         wa: WrapE<'a, Result<A, E1>, E0, Self>,
     ) -> WrapE<'a, A, Result<E1, E0>, Self> {
         Box::pin(async {

src/func/local.rs

@@ -3,10 +3,12 @@ use super::{controlflow::ControlFlowInstance, *};
 /// Represents wrapped results which are instantly available.
 pub trait LocalFunctor<'a>: WeakFunctor<'a> {
     /// Extract iteration state, if successful.
-    fn unstuff<A: 'a, B: 'a>(state: Self::F<ControlFlow<B, A>>) -> ControlFlow<Self::F<B>, A> {
+    fn unstuff<A: 'a + Send, B: 'a + Send>(
+        state: Self::F<ControlFlow<B, A>>,
+    ) -> ControlFlow<Self::F<B>, A> {
         Self::stuff::<_, ControlFlowInstance<_>>(state)
     }
 
     /// Stuff wrapped result into another functor.
-    fn stuff<A: 'a, T: Pure<'a>>(fa: Self::F<T::F<A>>) -> T::F<Self::F<A>>;
+    fn stuff<A: 'a + Send, T: Pure<'a>>(fa: Self::F<T::F<A>>) -> T::F<Self::F<A>>;
 }

src/func/shared.rs

@@ -2,35 +2,35 @@ use super::{weakfunctorany::WeakFunctorAny, WeakFunctor};
 pub use radn_derive::SharedFunctorAny;
 
 pub trait SharedFunctorAny: WeakFunctorAny {
-    type SharedAny<'a, A: 'a + Clone>: 'a + Clone
+    type SharedAny<'a, A: 'a + Send + Sync + Clone>: 'a + Send + Sync + Clone
     where
         Self: 'a;
 
-    fn share<'a, A: 'a + Clone>(fa: Self::FAny<'a, A>) -> Self::SharedAny<'a, A>
+    fn share<'a, A: 'a + Send + Sync + Clone>(fa: Self::FAny<'a, A>) -> Self::SharedAny<'a, A>
     where
         Self: 'a;
 
-    fn unshare<'a, A: 'a + Clone>(sa: Self::SharedAny<'a, A>) -> Self::FAny<'a, A>
+    fn unshare<'a, A: 'a + Send + Sync + Clone>(sa: Self::SharedAny<'a, A>) -> Self::FAny<'a, A>
     where
         Self: 'a;
 }
 
 pub trait SharedFunctor<'a>: WeakFunctor<'a> {
-    type Shared<A: 'a + Clone>: 'a + Clone;
+    type Shared<A: 'a + Send + Sync + Clone>: 'a + Send + Sync + Clone;
 
-    fn share<A: 'a + Clone>(fa: Self::F<A>) -> Self::Shared<A>;
+    fn share<A: 'a + Send + Sync + Clone>(fa: Self::F<A>) -> Self::Shared<A>;
 
-    fn unshare<A: 'a + Clone>(sa: Self::Shared<A>) -> Self::F<A>;
+    fn unshare<A: 'a + Send + Sync + Clone>(sa: Self::Shared<A>) -> Self::F<A>;
 }
 
 impl<'a, T: 'a + SharedFunctorAny> SharedFunctor<'a> for T {
-    type Shared<A: 'a + Clone> = T::SharedAny<'a, A>;
+    type Shared<A: 'a + Send + Sync + Clone> = T::SharedAny<'a, A>;
 
-    fn share<A: 'a + Clone>(fa: Self::F<A>) -> Self::Shared<A> {
+    fn share<A: 'a + Send + Sync + Clone>(fa: Self::F<A>) -> Self::Shared<A> {
         T::share(fa)
     }
 
-    fn unshare<A: 'a + Clone>(sa: Self::Shared<A>) -> Self::F<A> {
+    fn unshare<A: 'a + Send + Sync + Clone>(sa: Self::Shared<A>) -> Self::F<A> {
         T::unshare(sa)
     }
 }

src/func/test_suite.rs

@@ -2,7 +2,7 @@ use super::tests::*;
 use super::*;
 
 pub trait FunctorTestSuite<'a>: WeakFunctor<'a> + Eqr<'a> {
-    fn sample<A: 'a, F: FnMut(&'a dyn Fn(A) -> Self::F<A>)>(f: F);
+    fn sample<A: 'a + Send, F: FnMut(&'a (dyn Send + Sync + Fn(A) -> Self::F<A>))>(f: F);
 }
 
 pub fn functor_follows_laws<'a, T: Functor<'a> + FunctorTestSuite<'a>>() -> R {

src/func/tests.rs

@@ -27,7 +27,11 @@ impl R {
 }
 
 pub trait Eqr<'a>: WeakFunctor<'a> {
-    fn eqr<A: PartialEq + Debug + 'a>(name: &'a str, left: Self::F<A>, right: Self::F<A>) -> R;
+    fn eqr<A: 'a + Send + PartialEq + Debug>(
+        name: &'a str,
+        left: Self::F<A>,
+        right: Self::F<A>,
+    ) -> R;
 }
 
 pub fn eqr<T: PartialEq + Debug>(name: &str, left: T, right: T) -> R {
@@ -87,7 +91,7 @@ impl AddAssign<R> for R {
     }
 }
 
-pub fn fmap_respects_identity<'a, T: Functor<'a> + Eqr<'a>, A: 'a + Debug + PartialEq>(
+pub fn fmap_respects_identity<'a, T: Functor<'a> + Eqr<'a>, A: 'a + Send + Debug + PartialEq>(
     fa0: impl Fn() -> T::F<A>,
 ) -> R {
     T::eqr("identity: fmap id == id", T::fmap(fa0(), |a| a), fa0())
@@ -96,12 +100,12 @@ pub fn fmap_respects_identity<'a, T: Functor<'a> + Eqr<'a>, A: 'a + Debug + Part
 pub fn fmap_respects_composition<
     'a,
     T: Functor<'a> + Eqr<'a>,
-    A: 'a,
-    B: 'a,
-    C: 'a + Debug + PartialEq,
+    A: 'a + Send,
+    B: 'a + Send,
+    C: 'a + Send + Debug + PartialEq,
 >(
-    f: impl 'a + Copy + Fn(B) -> C,
-    g: impl 'a + Copy + Fn(A) -> B,
+    f: impl 'a + Send + Copy + Fn(B) -> C,
+    g: impl 'a + Send + Copy + Fn(A) -> B,
     fa0: impl Fn() -> T::F<A>,
 ) -> R {
     T::eqr(
@@ -111,7 +115,7 @@ pub fn fmap_respects_composition<
     )
 }
 
-pub fn seq_respects_identity<'a, T: Applicative<'a> + Eqr<'a>, A: 'a + Debug + PartialEq>(
+pub fn seq_respects_identity<'a, T: Applicative<'a> + Eqr<'a>, A: 'a + Send + Debug + PartialEq>(
     fa0: impl Fn() -> T::F<A>,
 ) -> R {
     T::eqr(
@@ -124,11 +128,11 @@ pub fn seq_respects_identity<'a, T: Applicative<'a> + Eqr<'a>, A: 'a + Debug + P
 pub fn seq_respects_composition<
     'a,
     T: Applicative<'a> + Eqr<'a>,
-    A: 'a,
-    B: 'a,
-    C: 'a + Debug + PartialEq,
-    F: 'a + Fn(B) -> C,
-    G: 'a + Fn(A) -> B,
+    A: 'a + Send,
+    B: 'a + Send,
+    C: 'a + Send + Debug + PartialEq,
+    F: 'a + Send + Fn(B) -> C,
+    G: 'a + Send + Fn(A) -> B,
 >(
     ff0: impl Fn() -> T::F<F>,
     fg0: impl Fn() -> T::F<G>,
@@ -147,8 +151,13 @@ pub fn seq_respects_composition<
     )
 }
 
-pub fn seq_is_homomorphic<'a, T: Applicative<'a> + Eqr<'a>, A: 'a, B: 'a + Debug + PartialEq>(
-    f: impl 'a + Fn(A) -> B,
+pub fn seq_is_homomorphic<
+    'a,
+    T: Applicative<'a> + Eqr<'a>,
+    A: 'a + Send,
+    B: 'a + Send + Debug + PartialEq,
+>(
+    f: impl 'a + Send + Fn(A) -> B,
     a0: impl Fn() -> A,
 ) -> R {
     T::eqr(
@@ -161,12 +170,12 @@ pub fn seq_is_homomorphic<'a, T: Applicative<'a> + Eqr<'a>, A: 'a, B: 'a + Debug
 pub fn seq_respects_interchange<
     'a,
     T: Applicative<'a> + Eqr<'a>,
-    A: 'a,
-    B: 'a + Debug + PartialEq,
-    F: 'a + Fn(A) -> B,
+    A: 'a + Send,
+    B: 'a + Send + Debug + PartialEq,
+    F: 'a + Send + Fn(A) -> B,
 >(
     ff0: impl Fn() -> T::F<F>,
-    a0: impl 'a + Fn() -> A,
+    a0: impl 'a + Send + Fn() -> A,
 ) -> R {
     T::eqr(
         "interchange: u <*> pure y = pure ($ y) <*> u",
@@ -178,9 +187,9 @@ pub fn seq_respects_interchange<
 pub fn seq_can_be_expressed_via_la2<
     'a,
     T: Applicative<'a> + Eqr<'a>,
-    A: 'a,
-    B: 'a + Debug + PartialEq,
-    F: 'a + Fn(A) -> B,
+    A: 'a + Send,
+    B: 'a + Send + Debug + PartialEq,
+    F: 'a + Send + Fn(A) -> B,
 >(
     ff0: impl Fn() -> T::F<F>,
     fa0: impl Fn() -> T::F<A>,
@@ -195,10 +204,10 @@ pub fn seq_can_be_expressed_via_la2<
 pub fn fmap_can_be_expressed_via_seq<
     'a,
     T: Applicative<'a> + Eqr<'a>,
-    A: 'a,
-    B: 'a + Debug + PartialEq,
+    A: 'a + Send,
+    B: 'a + Send + Debug + PartialEq,
 >(
-    f: impl 'a + Copy + Fn(A) -> B,
+    f: impl 'a + Send + Copy + Fn(A) -> B,
     fa0: impl Fn() -> T::F<A>,
 ) -> R {
     T::eqr(
@@ -211,8 +220,8 @@ pub fn fmap_can_be_expressed_via_seq<
 pub fn discard_can_be_expressed_via_seq_or_la2<
     'a,
     T: Applicative<'a> + Eqr<'a>,
-    A: 'a,
-    B: 'a + Debug + PartialEq,
+    A: 'a + Send,
+    B: 'a + Send + Debug + PartialEq,
 >(
     fa0: impl 'a + Fn() -> T::F<A>,
     fb0: impl 'a + Fn() -> T::F<B>,
@@ -228,8 +237,13 @@ pub fn discard_can_be_expressed_via_seq_or_la2<
     )
 }
 
-pub fn bind_respects_left_identity<'a, T: Monad<'a> + Eqr<'a>, A: 'a, B: 'a + Debug + PartialEq>(
-    f: impl 'a + Fn(A) -> T::F<B>,
+pub fn bind_respects_left_identity<
+    'a,
+    T: Monad<'a> + Eqr<'a>,
+    A: 'a + Send,
+    B: 'a + Send + Debug + PartialEq,
+>(
+    f: impl 'a + Send + Fn(A) -> T::F<B>,
     a0: impl Fn() -> A,
 ) -> R {
     T::eqr(
@@ -239,7 +253,11 @@ pub fn bind_respects_left_identity<'a, T: Monad<'a> + Eqr<'a>, A: 'a, B: 'a + De
     )
 }
 
-pub fn bind_respects_right_identity<'a, T: Monad<'a> + Eqr<'a>, A: 'a + Debug + PartialEq>(
+pub fn bind_respects_right_identity<
+    'a,
+    T: Monad<'a> + Eqr<'a>,
+    A: 'a + Send + Debug + PartialEq,
+>(
     fa0: impl Fn() -> T::F<A>,
 ) -> R {
     T::eqr(
@@ -249,10 +267,16 @@ pub fn bind_respects_right_identity<'a, T: Monad<'a> + Eqr<'a>, A: 'a + Debug +
     )
 }
 
-pub fn bind_is_associative<'a, T: Monad<'a> + Eqr<'a>, A: 'a, B: 'a, C: 'a + Debug + PartialEq>(
-    f: impl 'a + Clone + Fn(B) -> T::F<C>,
-    g: impl 'a + Clone + Fn(A) -> T::F<B>,
-    fa0: impl 'a + Fn() -> T::F<A>,
+pub fn bind_is_associative<
+    'a,
+    T: Monad<'a> + Eqr<'a>,
+    A: 'a + Send,
+    B: 'a + Send,
+    C: 'a + Send + Debug + PartialEq,
+>(
+    f: impl 'a + Send + Clone + Fn(B) -> T::F<C>,
+    g: impl 'a + Send + Clone + Fn(A) -> T::F<B>,
+    fa0: impl Fn() -> T::F<A>,
 ) -> R {
     T::eqr(
         r"associativity: m >>= (\x -> k x >>= h) = (m >>= k) >>= h",
@@ -264,12 +288,12 @@ pub fn bind_is_associative<'a, T: Monad<'a> + Eqr<'a>, A: 'a, B: 'a, C: 'a + Deb
 pub fn seq_can_be_expressed_via_bind<
     'a,
     T: Monad<'a> + Eqr<'a>,
-    A: 'a,
-    B: 'a + Debug + PartialEq,
-    F: 'a + Fn(A) -> B,
+    A: 'a + Send,
+    B: 'a + Send + Debug + PartialEq,
+    F: 'a + Send + Fn(A) -> B,
 >(
     ff0: impl Fn() -> T::F<F>,
-    fa0: impl 'a + Fn() -> T::F<A>,
+    fa0: impl 'a + Send + Fn() -> T::F<A>,
 ) -> R {
     T::eqr(
         r"seq via bind: m1 <*> m2 = m1 >>= (\x1 -> m2 >>= (\x2 -> pure (x1 x2)))",
@@ -281,11 +305,11 @@ pub fn seq_can_be_expressed_via_bind<
 pub fn fmap_can_be_expressed_via_bind<
     'a,
     T: Monad<'a> + Eqr<'a>,
-    A: 'a,
-    B: 'a + Debug + PartialEq,
+    A: 'a + Send,
+    B: 'a + Send + Debug + PartialEq,
 >(
-    f: impl 'a + Copy + Fn(A) -> B,
-    fa0: impl 'a + Fn() -> T::F<A>,
+    f: impl 'a + Send + Copy + Fn(A) -> B,
+    fa0: impl Fn() -> T::F<A>,
 ) -> R {
     T::eqr(
         "fmap via bind: fmap f xs  =  xs >>= return . f",

src/func/weakfunctorany.rs

@@ -1,12 +1,12 @@
 use super::WeakFunctor;
 
-pub trait WeakFunctorAny {
+pub trait WeakFunctorAny: Send {
     /// Type of the wrapped value.
-    type FAny<'a, A: 'a>: 'a
+    type FAny<'a, A: 'a + Send>: 'a + Send
     where
         Self: 'a;
 }
 
 impl<'a, T: ?Sized + 'a + WeakFunctorAny> WeakFunctor<'a> for T {
-    type F<A: 'a> = T::FAny<'a, A>;
+    type F<A: 'a + Send> = T::FAny<'a, A>;
 }

src/mrds/trees/heighted.rs

@@ -1,4 +1,4 @@
-use std::{fmt::Display, marker::PhantomData, rc::Rc};
+use std::{fmt::Display, marker::PhantomData, sync::Arc};
 
 use crate::flow::{
     binary::{balancing::*, bound::*, *},
@@ -20,7 +20,7 @@ impl<A: Display> Display for Node<A> {
 }
 
 struct Reference<A> {
-    node: Rc<Node<A>>,
+    node: Arc<Node<A>>,
 }
 
 impl<A> Clone for Reference<A> {
@@ -76,11 +76,11 @@ impl<A> Clone for Trees<A> {
     }
 }
 
-impl<'a, A: 'a> FunctorContext<'a> for Trees<A> {
+impl<'a, A: 'a + Send> FunctorContext<'a> for Trees<A> {
     type T = instances::solo::SoloInstance;
 }
 
-impl<'a, A: 'a + Ord + Clone> BinaryTrees<'a> for Trees<A> {
+impl<'a, A: 'a + Send + Sync + Ord + Clone> BinaryTrees<'a> for Trees<A> {
     type Node = Node<A>;
 
     type Reference = Reference<A>;
@@ -114,17 +114,17 @@ impl<'a, A: 'a + Ord + Clone> BinaryTrees<'a> for Trees<A> {
     }
 }
 
-impl<'a, A: 'a + Ord + Clone> BinaryTreesHeight<'a> for Trees<A> {
+impl<'a, A: 'a + Send + Sync + Ord + Clone> BinaryTreesHeight<'a> for Trees<A> {
     fn height(&self, tree: &Self::Tree) -> u64 {
         tree.height
     }
 
-    fn height_error<T: 'a>(&self, error: HeightError) -> BTWrap<'a, Self, T> {
+    fn height_error<T: 'a + Send>(&self, error: HeightError) -> BTWrap<'a, Self, T> {
         panic!("{error}")
     }
 }
 
-impl<'a, A: 'a + Ord + Clone> BinaryTreesEmpty<'a> for Trees<A> {
+impl<'a, A: 'a + Send + Sync + Ord + Clone> BinaryTreesEmpty<'a> for Trees<A> {
     fn empty(&self) -> Self::Tree {
         Tree {
             reference: None,
@@ -141,7 +141,7 @@ impl<'a, A: 'a + Ord + Clone> BinaryTreesEmpty<'a> for Trees<A> {
     }
 }
 
-impl<'a, A: 'a + Ord + Clone> BinaryTreesTryJoin<'a> for Trees<A> {
+impl<'a, A: 'a + Send + Sync + Ord + Clone> BinaryTreesTryJoin<'a> for Trees<A> {
     fn try_join(
         &self,
         tl: Self::Tree,
@@ -152,17 +152,17 @@ impl<'a, A: 'a + Ord + Clone> BinaryTreesTryJoin<'a> for Trees<A> {
     }
 }
 
-impl<'a, A: 'a + Ord + Clone> BinaryTreesUnbalanced<'a> for Trees<A> {
+impl<'a, A: 'a + Send + Sync + Ord + Clone> BinaryTreesUnbalanced<'a> for Trees<A> {
     fn tree_of_with_height(&self, node: Self::Node, height: u64) -> BTWrap<'a, Self, Self::Tree> {
         Tree {
             reference: Some(Reference {
-                node: Rc::new(node),
+                node: Arc::new(node),
             }),
             height,
         }
     }
 
-    fn balancing_error<T: 'a>(&self, _error: BalancingError) -> BTWrap<'a, Self, T> {
+    fn balancing_error<T: 'a + Send>(&self, _error: BalancingError) -> BTWrap<'a, Self, T> {
         panic!("balancing error")
     }
 
@@ -171,8 +171,11 @@ impl<'a, A: 'a + Ord + Clone> BinaryTreesUnbalanced<'a> for Trees<A> {
     }
 }
 
-impl<'a, A: 'a + Ord + Clone> BinaryTreesBindable<'a> for Trees<A> {
-    fn bounds_error<T: 'a>(&self, _error: bounds::BoundsError<Self::Key>) -> BTWrap<'a, Self, T> {
+impl<'a, A: 'a + Send + Sync + Ord + Clone> BinaryTreesBindable<'a> for Trees<A> {
+    fn bounds_error<T: 'a + Send>(
+        &self,
+        _error: bounds::BoundsError<Self::Key>,
+    ) -> BTWrap<'a, Self, T> {
         panic!("bounds violated");
     }
 }

src/mrds/trees/unbalanced.rs

@@ -2,7 +2,7 @@
 //!
 //! Intended for testing.
 
-use std::{fmt::Display, rc::*};
+use std::{fmt::Display, sync::Arc};
 
 use crate::flow::traversible::*;
 use crate::func::*;
@@ -20,24 +20,24 @@ impl PartialEq for UnbalancedData {
     }
 }
 
-pub struct UnbalancedNode<'a, T: Monad<'a>, A: 'a> {
-    cl: Rc<UnbalancedTree<'a, T, A>>,
-    cr: Rc<UnbalancedTree<'a, T, A>>,
+pub struct UnbalancedNode<'a, T: Monad<'a>, A: 'a + Send + Sync> {
+    cl: Arc<UnbalancedTree<'a, T, A>>,
+    cr: Arc<UnbalancedTree<'a, T, A>>,
     key: A,
 }
 
-pub type UnbalancedResolution<'a, T, A> = Wrap<'a, Rc<UnbalancedNode<'a, T, A>>, T>;
+pub type UnbalancedResolution<'a, T, A> = Wrap<'a, Arc<UnbalancedNode<'a, T, A>>, T>;
 
-pub struct UnbalancedReference<'a, T: Monad<'a>, A: 'a>(
-    Box<dyn 'a + Fn() -> UnbalancedResolution<'a, T, A>>,
+pub struct UnbalancedReference<'a, T: Monad<'a>, A: 'a + Send + Sync>(
+    Box<dyn 'a + Send + Sync + Fn() -> UnbalancedResolution<'a, T, A>>,
 );
 
-pub enum UnbalancedTree<'a, T: Monad<'a>, A: 'a> {
+pub enum UnbalancedTree<'a, T: Monad<'a>, A: 'a + Send + Sync> {
     Leaf,
-    Node(Rc<UnbalancedReference<'a, T, A>>),
+    Node(Arc<UnbalancedReference<'a, T, A>>),
 }
 
-impl<'a, T: Monad<'a>, A: 'a + Display> Display for UnbalancedNode<'a, T, A>
+impl<'a, T: Monad<'a>, A: 'a + Send + Sync + Display> Display for UnbalancedNode<'a, T, A>
 where
     UnbalancedReference<'a, T, A>: std::fmt::Display,
 {
@@ -46,7 +46,7 @@ where
     }
 }
 
-impl<'a, T: Monad<'a>, A: 'a + Display> Display for UnbalancedTree<'a, T, A>
+impl<'a, T: Monad<'a>, A: 'a + Send + Sync + Display> Display for UnbalancedTree<'a, T, A>
 where
     UnbalancedReference<'a, T, A>: std::fmt::Display,
 {
@@ -58,13 +58,15 @@ where
     }
 }
 
-impl<'a, A: 'a + Display> Display for UnbalancedReference<'a, instances::solo::SoloInstance, A> {
+impl<'a, A: 'a + Send + Sync + Display> Display
+    for UnbalancedReference<'a, instances::solo::SoloInstance, A>
+{
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         write!(f, "{}", self.0())
     }
 }
 
-impl<'a, A: 'a + Display> Display
+impl<'a, A: 'a + Send + Sync + Display> Display
     for UnbalancedReference<'a, instances::result::ResultInstance<()>, A>
 {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
@@ -75,24 +77,24 @@ impl<'a, A: 'a + Display> Display
     }
 }
 
-impl<'a, T: Monad<'a>, A: 'a + Clone> TraversibleBinaryNode<'a, T, A, UnbalancedData>
+impl<'a, T: Monad<'a>, A: 'a + Send + Sync + Clone> TraversibleBinaryNode<'a, T, A, UnbalancedData>
     for UnbalancedNode<'a, T, A>
 {
     fn split(&self) -> Split<'a, T, A, UnbalancedData> {
         (self.cl.clone(), self.cr.clone(), self.key.clone())
     }
 
-    fn to_tree(self: Rc<Self>) -> Rc<dyn TraversibleBinaryTree<'a, T, A, UnbalancedData>> {
-        Rc::new(UnbalancedTree::Node(Rc::new(UnbalancedReference(
+    fn to_tree(self: Arc<Self>) -> Arc<dyn TraversibleBinaryTree<'a, T, A, UnbalancedData>> {
+        Arc::new(UnbalancedTree::Node(Arc::new(UnbalancedReference(
             Box::new(move || T::pure(self.clone())),
         ))))
     }
 }
 
-impl<'a, T: Monad<'a>, A: 'a + Clone> TraversibleBinaryReference<'a, T, A, UnbalancedData>
-    for UnbalancedReference<'a, T, A>
+impl<'a, T: Monad<'a>, A: 'a + Send + Sync + Clone>
+    TraversibleBinaryReference<'a, T, A, UnbalancedData> for UnbalancedReference<'a, T, A>
 {
-    fn resolve(&self) -> Wrap<'a, Rc<dyn TraversibleBinaryNode<'a, T, A, UnbalancedData>>, T> {
+    fn resolve(&self) -> Wrap<'a, Arc<dyn TraversibleBinaryNode<'a, T, A, UnbalancedData>>, T> {
         <T as Functor>::fmap(self.0(), |rc| rc as _)
     }
 
@@ -101,10 +103,10 @@ impl<'a, T: Monad<'a>, A: 'a + Clone> TraversibleBinaryReference<'a, T, A, Unbal
     }
 }
 
-impl<'a, T: Monad<'a>, A: 'a + Clone> TraversibleBinaryTree<'a, T, A, UnbalancedData>
+impl<'a, T: Monad<'a>, A: 'a + Send + Sync + Clone> TraversibleBinaryTree<'a, T, A, UnbalancedData>
     for UnbalancedTree<'a, T, A>
 {
-    fn refer(&self) -> Option<Rc<dyn TraversibleBinaryReference<'a, T, A, UnbalancedData>>> {
+    fn refer(&self) -> Option<Arc<dyn TraversibleBinaryReference<'a, T, A, UnbalancedData>>> {
         match self {
             Self::Leaf => None,
             Self::Node(reference) => Some(reference.clone()),
@@ -113,39 +115,42 @@ impl<'a, T: Monad<'a>, A: 'a + Clone> TraversibleBinaryTree<'a, T, A, Unbalanced
 }
 
 type WrapType<'a, T, A> = Box<
-    dyn 'a + Fn(Rc<UnbalancedNode<'a, T, A>>) -> Box<dyn Fn() -> UnbalancedResolution<'a, T, A>>,
+    dyn 'a
+        + Fn(
+            Arc<UnbalancedNode<'a, T, A>>,
+        ) -> Box<dyn Send + Sync + Fn() -> UnbalancedResolution<'a, T, A>>,
 >;
 
-pub struct UnbalancedConstructor<'a, T: Monad<'a>, A: 'a> {
+pub struct UnbalancedConstructor<'a, T: Monad<'a>, A: 'a + Send + Sync> {
     wrap: WrapType<'a, T, A>,
 }
 
-impl<'a, T: Monad<'a>, A: 'a> UnbalancedConstructor<'a, T, A> {
-    pub fn rc(wrap: WrapType<'a, T, A>) -> Rc<Self> {
+impl<'a, T: Monad<'a>, A: 'a + Send + Sync> UnbalancedConstructor<'a, T, A> {
+    pub fn rc(wrap: WrapType<'a, T, A>) -> Arc<Self> {
         Self { wrap }.into()
     }
 
-    pub fn leaf(&self) -> Rc<UnbalancedTree<'a, T, A>> {
+    pub fn leaf(&self) -> Arc<UnbalancedTree<'a, T, A>> {
         UnbalancedTree::Leaf.into()
     }
 
     pub fn node(
-        self: &Rc<Self>,
-        cl: Rc<UnbalancedTree<'a, T, A>>,
+        self: &Arc<Self>,
+        cl: Arc<UnbalancedTree<'a, T, A>>,
         key: A,
-        cr: Rc<UnbalancedTree<'a, T, A>>,
-    ) -> Rc<UnbalancedTree<'a, T, A>> {
-        let node = Rc::new(UnbalancedNode { cl, cr, key });
+        cr: Arc<UnbalancedTree<'a, T, A>>,
+    ) -> Arc<UnbalancedTree<'a, T, A>> {
+        let node = Arc::new(UnbalancedNode { cl, cr, key });
         let ctr = self.clone();
-        UnbalancedTree::Node(Rc::new(UnbalancedReference((ctr.wrap)(node)))).into()
+        UnbalancedTree::Node(Arc::new(UnbalancedReference((ctr.wrap)(node)))).into()
     }
 
     #[cfg(test)]
     pub fn from_slice<R: 'a + rand::Rng>(
-        self: &Rc<Self>,
+        self: &Arc<Self>,
         rng: &mut R,
         slice: &[A],
-    ) -> Rc<UnbalancedTree<'a, T, A>>
+    ) -> Arc<UnbalancedTree<'a, T, A>>
     where
         A: 'a + Clone,
     {
@@ -175,7 +180,7 @@ mod tests {
 
     #[test]
     fn test_simple_slices() {
-        let ctr: Rc<UnbalancedConstructor<instances::result::ResultInstance<()>, _>> =
+        let ctr: Arc<UnbalancedConstructor<instances::result::ResultInstance<()>, _>> =
             UnbalancedConstructor::rc(Box::new(|node| Box::new(move || Ok(node.clone()))));
         let mut rng = rand::thread_rng();
         let t_set = ctr.from_slice(&mut rng, &[0]);
@@ -207,7 +212,7 @@ mod tests {
 
     #[test]
     fn test_random_slices() {
-        let ctr: Rc<UnbalancedConstructor<instances::result::ResultInstance<()>, _>> =
+        let ctr: Arc<UnbalancedConstructor<instances::result::ResultInstance<()>, _>> =
             UnbalancedConstructor::rc(Box::new(|node| Box::new(move || Ok(node.clone()))));
         let mut rng = rand::thread_rng();
         for _ in 0..1000 {
@@ -256,7 +261,7 @@ mod tests {
 
     #[test]
     fn trace_one_slice() {
-        let ctr: Rc<UnbalancedConstructor<TracedMonad, _>> =
+        let ctr: Arc<UnbalancedConstructor<TracedMonad, _>> =
             UnbalancedConstructor::rc(Box::new(|node| {
                 Box::new(move || TracedMonad::pure(node.clone()).after_resolution())
             }));

src/rcore.rs

@@ -18,7 +18,7 @@ mod regular;
 mod resolution;
 mod resolver_origin;
 
-use std::{error::Error, rc::Rc};
+use std::{error::Error, sync::Arc};
 
 use crate::func::context::*;
 use crate::func::*;
@@ -48,7 +48,7 @@ pub use self::resolution::{
 pub type Wrapped<'a, Ctx, A> = WrapC<'a, A, Ctx>;
 
 /// [Mentionable] base.
-pub trait MentionableBase<'a, Ctx: Context<'a>>: 'a + Serializable + Sized {
+pub trait MentionableBase<'a, Ctx: Context<'a>>: 'a + Send + Sync + Serializable + Sized {
     /// Type of the associated factory.
     type Fctr: FactoryBase<'a, Ctx, Mtbl = Self>;
 
@@ -104,7 +104,7 @@ pub trait FactoryBase<'a, Ctx: Context<'a>>: 'a + Send + Sync + Clone {
     /// Type of the associated objects.
     type Mtbl: MentionableBase<'a, Ctx, Fctr = Self>;
     /// Type of an error that [`FactoryParse::deserialize`] can fail with.
-    type ParseError: 'a + Error;
+    type ParseError: 'a + Send + Error;
 }
 
 /// [Factory] that allows parsing consuming the parser.
@@ -141,6 +141,6 @@ pub trait FactoryExt<'a, Ctx: Context<'a>>: FactoryParse<'a, Ctx> {
     fn parse_slice(
         &self,
         slice: &[u8],
-        resolver: &Rc<dyn Resolver<'a, Ctx>>,
+        resolver: &Arc<dyn Resolver<'a, Ctx>>,
     ) -> ParseResult<'a, Ctx, Self>;
 }

src/rcore/addresses.rs

@@ -44,7 +44,7 @@ pub(super) trait InliningAddresses<E>: Stream {
     fn inext_point<'a, Ctx: Context<'a>, A: MentionableBase<'a, Ctx>>(
         self,
         addresses: &mut Addresses,
-        resolver: Rc<dyn Resolver<'a, Ctx>>,
+        resolver: Arc<dyn Resolver<'a, Ctx>>,
         factory: A::Fctr,
         err: impl FnOnce(&[u8]) -> E,
     ) -> Result<(Point<'a, Ctx, A>, Self), E> {
@@ -58,7 +58,7 @@ impl<E, D: ?Sized + Stream> InliningAddresses<E> for D {}
 fn _parse_slice<'a, Ctx: Context<'a>, F: FactoryParse<'a, Ctx>>(
     factory: &F,
     slice: &[u8],
-    resolver: &Rc<dyn Resolver<'a, Ctx>>,
+    resolver: &Arc<dyn Resolver<'a, Ctx>>,
 ) -> ParseResult<'a, Ctx, F> {
     let mut deserializer = SliceDeserializer::from(slice);
     let mentionable = factory.deserialize(&mut DeCtxT {
@@ -78,7 +78,7 @@ impl<'a, Ctx: Context<'a>, F: FactoryParse<'a, Ctx>> FactoryExt<'a, Ctx> for F {
     fn parse_slice(
         &self,
         slice: &[u8],
-        resolver: &Rc<dyn Resolver<'a, Ctx>>,
+        resolver: &Arc<dyn Resolver<'a, Ctx>>,
     ) -> ParseResult<'a, Ctx, Self> {
         _parse_slice::<Ctx, _>(self, slice, resolver)
     }

src/rcore/context.rs

@@ -9,7 +9,7 @@ pub trait Context<'a>: FallibleCtx<'a, T = Self::_Tm> {
     type D: Diagnostic<'a, Self::T>;
 
     /// Type to represent resolution errors mainly arising in [`Resolver::resolve`].
-    type LookupError: 'a + Error;
+    type LookupError: 'a + Send + Error;
 
     /// Get [type@Hash] of a slice, mostly for use in [`Point`].
     fn hash(s: &[u8]) -> Hash;

src/rcore/dectx.rs

@@ -2,7 +2,7 @@ use super::*;
 
 pub(super) struct DeCtxT<'a: 'c, 'c, Ctx: Context<'a>> {
     pub deserializer: &'c mut dyn Deserializer,
-    pub resolver: &'c Rc<dyn Resolver<'a, Ctx>>,
+    pub resolver: &'c Arc<dyn Resolver<'a, Ctx>>,
     pub addresses: &'c mut Addresses,
 }
 
@@ -13,7 +13,7 @@ pub(super) trait DeCtx<'a, Ctx: Context<'a>> {
 
     fn next_address(&mut self) -> Result<Address, &[u8]>;
 
-    fn resolver(&self) -> Rc<dyn Resolver<'a, Ctx>>;
+    fn resolver(&self) -> Arc<dyn Resolver<'a, Ctx>>;
 
     fn ad(&mut self) -> (&mut Addresses, &mut dyn Deserializer);
 }
@@ -31,7 +31,7 @@ impl<'a: 'c, 'c, Ctx: Context<'a>> DeCtx<'a, Ctx> for DeCtxT<'a, 'c, Ctx> {
         self.addresses.next(self.deserializer)
     }
 
-    fn resolver(&self) -> Rc<dyn Resolver<'a, Ctx>> {
+    fn resolver(&self) -> Arc<dyn Resolver<'a, Ctx>> {
         self.resolver.clone()
     }
 

src/rcore/demoted.rs

@@ -38,7 +38,7 @@ impl<'a: 'c, 'c, Ctx: Context<'a>> InCtx<'a, Ctx> for Demoted<'a, 'c, Ctx> {
         Ok((point, Self(dectx)))
     }
 
-    fn iresolver(&self) -> Rc<dyn Resolver<'a, Ctx>> {
+    fn iresolver(&self) -> Arc<dyn Resolver<'a, Ctx>> {
         self.0.iresolver()
     }
 

src/rcore/diagnostic.rs

@@ -1,17 +1,17 @@
 use crate::func::Monad;
 
 /// Basic support for tracing events across the execution.
-pub trait Diagnostic<'a, T: Monad<'a>> {
+pub trait Diagnostic<'a, T: Monad<'a>>: 'a + Send {
     /// Specify that the evaluation happens after a specific event.
-    fn after<'b, A: 'a>(fa: T::F<A>, event: impl 'b + FnOnce() -> String) -> T::F<A>
+    fn after<'b, A: 'a + Send>(fa: T::F<A>, event: impl 'b + FnOnce() -> String) -> T::F<A>
     where
         'a: 'b;
     /// Specify that the evaluation happens before a specific event.
-    fn before<'b, A: 'a>(fa: T::F<A>, event: impl 'b + FnOnce() -> String) -> T::F<A>
+    fn before<'b, A: 'a + Send>(fa: T::F<A>, event: impl 'b + FnOnce() -> String) -> T::F<A>
     where
         'a: 'b;
     /// Label the evaluation step as a specific named action.
-    fn wrapped<'b, A: 'a>(fa: T::F<A>, event: impl 'b + FnOnce() -> String) -> T::F<A>
+    fn wrapped<'b, A: 'a + Send>(fa: T::F<A>, event: impl 'b + FnOnce() -> String) -> T::F<A>
     where
         'a: 'b;
 }

src/rcore/inctx.rs

@@ -19,7 +19,7 @@ pub trait InCtx<'a, Ctx: Context<'a>>: Stream {
     }
 
     /// Clone the reference to the current [Resolver].
-    fn iresolver(&self) -> Rc<dyn Resolver<'a, Ctx>>;
+    fn iresolver(&self) -> Arc<dyn Resolver<'a, Ctx>>;
 
     /// Return [Demoted] version of the context.
     fn demote<'d>(self) -> Demoted<'a, 'd, Ctx>
@@ -59,7 +59,7 @@ impl<'a: 'c, 'c, Ctx: Context<'a>> InCtx<'a, Ctx> for &'c mut dyn DeCtx<'a, Ctx>
         }
     }
 
-    fn iresolver(&self) -> Rc<dyn Resolver<'a, Ctx>> {
+    fn iresolver(&self) -> Arc<dyn Resolver<'a, Ctx>> {
         self.resolver()
     }
 

src/rcore/origin.rs

@@ -1,17 +1,17 @@
 use super::*;
 
 /// Represents a potentially resolvable [`Mentionable`].
-pub trait Origin<'a, Ctx: Context<'a>>: 'a {
+pub trait Origin<'a, Ctx: Context<'a>>: 'a + Send + Sync {
     /// Type of the associated object.
     type Mtbl: MentionableBase<'a, Ctx>;
     /// Clone the associated factory.
     fn factory(&self) -> OFctr<'a, Ctx, Self>;
     /// Try resolving the value.
-    fn resolve(self: Rc<Self>) -> Resolution<'a, Ctx, Self::Mtbl>
+    fn resolve(self: Arc<Self>) -> Resolution<'a, Ctx, Self::Mtbl>
     where
         OFctr<'a, Ctx, Self>: FactoryParse<'a, Ctx>;
     /// Try resolving the bytes. Should avoid parsing the value.
-    fn resolve_bytes(self: Rc<Self>) -> HashResolution<'a, Ctx>;
+    fn resolve_bytes(self: Arc<Self>) -> HashResolution<'a, Ctx>;
 }
 
 /// Type of the [`Factory`] associated with the [`Origin`].
@@ -19,16 +19,16 @@ pub type OFctr<'a, Ctx, O> = Fctr<'a, Ctx, <O as Origin<'a, Ctx>>::Mtbl>;
 
 /// [`OriginMap::resolve_map`].
 pub trait OriginMap<'a, Ctx: Context<'a>>: Origin<'a, Ctx> {
-    fn ref_resolve(self: &Rc<Self>) -> Resolution<'a, Ctx, Self::Mtbl>
+    fn ref_resolve(self: &Arc<Self>) -> Resolution<'a, Ctx, Self::Mtbl>
     where
         OFctr<'a, Ctx, Self>: FactoryParse<'a, Ctx>,
     {
         self.clone().resolve()
     }
 
-    fn resolve_map<T>(
-        self: &Rc<Self>,
-        f: impl 'a + FnOnce(ResolutionResult<'a, Ctx, Self::Mtbl>) -> T,
+    fn resolve_map<T: 'a + Send>(
+        self: &Arc<Self>,
+        f: impl 'a + Send + FnOnce(ResolutionResult<'a, Ctx, Self::Mtbl>) -> T,
     ) -> Wrapped<'a, Ctx, T>
     where
         OFctr<'a, Ctx, Self>: FactoryParse<'a, Ctx>,

src/rcore/point.rs

@@ -7,7 +7,7 @@ pub struct Point<'a, Ctx: Context<'a>, A: MentionableBase<'a, Ctx>> {
     /// and its topology ([`MentionableTop::topology`]).
     pub point: Hash,
     /// [Origin] used in [`Point::resolve`].
-    pub origin: Rc<dyn Origin<'a, Ctx, Mtbl = A>>,
+    pub origin: Arc<dyn Origin<'a, Ctx, Mtbl = A>>,
 }
 
 impl<'a, Ctx: Context<'a>, A: MentionableBase<'a, Ctx>> PartialEq for Point<'a, Ctx, A> {
@@ -36,9 +36,9 @@ where
     }
 
     /// Resolve the object, then map the [ResolutionResult].
-    pub fn resolve_map<B: 'a>(
+    pub fn resolve_map<B: 'a + Send>(
         &self,
-        f: impl 'a + FnOnce(ResolutionResult<'a, Ctx, A>) -> B,
+        f: impl 'a + Send + FnOnce(ResolutionResult<'a, Ctx, A>) -> B,
     ) -> Wrapped<'a, Ctx, B> {
         self.origin.resolve_map(f)
     }

src/rcore/resolution.rs

@@ -27,7 +27,7 @@ pub type ResolutionFailure<'a, Ctx, A> =
     ResolutionError<LookupError<'a, Ctx>, ParseErrorA<'a, Ctx, A>>;
 
 /// Result yielded by [`Origin`].
-pub type ResolutionResult<'a, Ctx, A> = Result<Rc<A>, ResolutionFailure<'a, Ctx, A>>;
+pub type ResolutionResult<'a, Ctx, A> = Result<Arc<A>, ResolutionFailure<'a, Ctx, A>>;
 
 /// Wrapped result returned by [`Origin`].
 pub type Resolution<'a, Ctx, A> = Wrapped<'a, Ctx, ResolutionResult<'a, Ctx, A>>;
@@ -35,7 +35,7 @@ pub type Resolution<'a, Ctx, A> = Wrapped<'a, Ctx, ResolutionResult<'a, Ctx, A>>
 /// Underlying [`Result`] of [`HashResolution`].
 /// In case of success, contains byte data and the resolver for points appearing inside that data.
 pub type HashResolutionResult<'a, Ctx> =
-    Result<(Vec<u8>, Rc<dyn Resolver<'a, Ctx>>), LookupError<'a, Ctx>>;
+    Result<(Vec<u8>, Arc<dyn Resolver<'a, Ctx>>), LookupError<'a, Ctx>>;
 
 /// Shorthand for the type of values returned by [`Resolver::resolve`].
 pub type HashResolution<'a, Ctx> = Wrapped<'a, Ctx, HashResolutionResult<'a, Ctx>>;
@@ -49,19 +49,19 @@ pub struct Address {
 }
 
 /// Trait representing the "rainbow table" behaviour.
-pub trait Resolver<'a, Ctx: Context<'a>>: 'a {
+pub trait Resolver<'a, Ctx: Context<'a>>: 'a + Send + Sync {
     /// Successfully returned value should be the inverse of the point passed
     /// with topology header ([`MentionableTop::topology()`]) omitted.
-    fn resolve(self: Rc<Self>, address: Address) -> HashResolution<'a, Ctx>;
+    fn resolve(self: Arc<Self>, address: Address) -> HashResolution<'a, Ctx>;
 }
 
 /// [`ResolverMap::resolve_map`].
 pub trait ResolverMap<'a, Ctx: Context<'a>>: Resolver<'a, Ctx> {
     /// Resolve the [Address], then map the [`HashResolutionResult`].
-    fn resolve_map<T>(
-        self: Rc<Self>,
+    fn resolve_map<T: 'a + Send>(
+        self: Arc<Self>,
         address: Address,
-        f: impl 'a + FnOnce(HashResolutionResult<'a, Ctx>) -> T,
+        f: impl 'a + Send + FnOnce(HashResolutionResult<'a, Ctx>) -> T,
     ) -> Wrapped<'a, Ctx, T> {
         Ctx::fmap(self.resolve(address), f)
     }

src/rcore/resolver_origin.rs

@@ -8,11 +8,11 @@ where
     pub fn from_address(
         address: Address,
         factory: A::Fctr,
-        resolver: Rc<dyn Resolver<'a, Ctx>>,
+        resolver: Arc<dyn Resolver<'a, Ctx>>,
     ) -> Self {
         Point {
             point: address.point,
-            origin: Rc::new(ResolverOrigin {
+            origin: Arc::new(ResolverOrigin {
                 r_factory: factory,
                 r_address: address,
                 r_resolver: resolver,
@@ -24,11 +24,11 @@ where
 struct ResolverOrigin<'a, Ctx: Context<'a>, F: FactoryBase<'a, Ctx>> {
     r_factory: F,
     r_address: Address,
-    r_resolver: Rc<dyn Resolver<'a, Ctx>>,
+    r_resolver: Arc<dyn Resolver<'a, Ctx>>,
 }
 
 fn _resolve_origin<'a, Ctx: Context<'a>, F: FactoryParse<'a, Ctx>>(
-    origin: Rc<ResolverOrigin<'a, Ctx, F>>,
+    origin: Arc<ResolverOrigin<'a, Ctx, F>>,
 ) -> Resolution<'a, Ctx, F::Mtbl> {
     origin
         .r_resolver
@@ -39,7 +39,7 @@ fn _resolve_origin<'a, Ctx: Context<'a>, F: FactoryParse<'a, Ctx>>(
                 .r_factory
                 .parse_slice(&src, &resolver)
                 .map_err(ResolutionError::Parse)?;
-            Ok(Rc::new(mentionable))
+            Ok(Arc::new(mentionable))
         })
 }
 
@@ -50,14 +50,14 @@ impl<'a, Ctx: Context<'a>, F: FactoryBase<'a, Ctx>> Origin<'a, Ctx> for Resolver
         self.r_factory.clone()
     }
 
-    fn resolve(self: Rc<Self>) -> Resolution<'a, Ctx, Self::Mtbl>
+    fn resolve(self: Arc<Self>) -> Resolution<'a, Ctx, Self::Mtbl>
     where
         F: FactoryParse<'a, Ctx>,
     {
         _resolve_origin(self)
     }
 
-    fn resolve_bytes(self: Rc<Self>) -> HashResolution<'a, Ctx> {
+    fn resolve_bytes(self: Arc<Self>) -> HashResolution<'a, Ctx> {
         self.r_resolver.clone().resolve(self.r_address)
     }
 }

src/rstd.rs

@@ -16,7 +16,7 @@ pub mod tracing;
 pub mod typeless;
 mod wrapped_origin;
 
-use std::{error::Error, fmt::Display, rc::Rc};
+use std::{error::Error, fmt::Display, sync::Arc};
 
 use crate::func::*;
 use crate::mode::*;
@@ -44,12 +44,12 @@ impl<S: Serializable> SerializableExt for S {
 
 /// [`ResolverExt::into_rc`].
 pub trait ResolverExt<'a, Ctx: Context<'a>>: Resolver<'a, Ctx> {
-    /// Wrap the resolver into [`Rc`].
-    fn into_rc(self) -> Rc<dyn Resolver<'a, Ctx>>;
+    /// Wrap the resolver into [`Arc`].
+    fn into_rc(self) -> Arc<dyn Resolver<'a, Ctx>>;
 }
 
 impl<'a, Ctx: Context<'a>, R: Resolver<'a, Ctx>> ResolverExt<'a, Ctx> for R {
-    fn into_rc(self) -> Rc<dyn Resolver<'a, Ctx>> {
-        Rc::new(self)
+    fn into_rc(self) -> Arc<dyn Resolver<'a, Ctx>> {
+        Arc::new(self)
     }
 }

src/rstd/cast.rs

@@ -83,8 +83,8 @@ impl<'a> CastError<'a> {
 }
 
 impl<'a, Ctx: CastCtx<'a>> CastResolver<'a, Ctx> {
-    fn rc(points: Vec<Point<'a, Ctx, TypelessMentionable<'a, Ctx>>>) -> Rc<dyn Resolver<'a, Ctx>> {
-        Rc::new(Self { points })
+    fn rc(points: Vec<Point<'a, Ctx, TypelessMentionable<'a, Ctx>>>) -> Arc<dyn Resolver<'a, Ctx>> {
+        Arc::new(Self { points })
     }
 
     fn _get_point(
@@ -138,7 +138,7 @@ fn map_resolved<'a, Ctx: CastCtx<'a>>(
 }
 
 impl<'a, Ctx: CastCtx<'a>> Resolver<'a, Ctx> for CastResolver<'a, Ctx> {
-    fn resolve(self: Rc<Self>, address: Address) -> HashResolution<'a, Ctx> {
+    fn resolve(self: Arc<Self>, address: Address) -> HashResolution<'a, Ctx> {
         let point = match self.get_point(address) {
             Ok(point) => point,
             Err(cast_error) => return cast_error.pure::<Ctx>(),
@@ -151,7 +151,7 @@ impl<'a, Ctx: CastCtx<'a>> TypelessMentionable<'a, Ctx> {
     pub fn cast_full<A: Mentionable<'a, Ctx>>(
         &self,
         factory: A::Fctr,
-        map_resolver: impl FnOnce(Rc<dyn Resolver<'a, Ctx>>) -> Rc<dyn Resolver<'a, Ctx>>,
+        map_resolver: impl FnOnce(Arc<dyn Resolver<'a, Ctx>>) -> Arc<dyn Resolver<'a, Ctx>>,
     ) -> ParseResultA<'a, Ctx, A> {
         factory.parse_slice(
             &self.bytes(),
@@ -183,20 +183,20 @@ fn cast_resolved<'a, Ctx: CastCtx<'a>, A: Mentionable<'a, Ctx>>(
         .map_err(ResolutionError::Lookup)?
         .cast(factory)
         .map_err(ResolutionError::Parse)
-        .map(Rc::new)
+        .map(Arc::new)
 }
 
 fn cast_resolve<'a, Ctx: CastCtx<'a>, A: Mentionable<'a, Ctx>>(
-    typeless_origin: Rc<dyn Origin<'a, Ctx, Mtbl = TypelessMentionable<'a, Ctx>>>,
+    typeless_origin: Arc<dyn Origin<'a, Ctx, Mtbl = TypelessMentionable<'a, Ctx>>>,
     factory: A::Fctr,
 ) -> Resolution<'a, Ctx, A> {
     typeless_origin.resolve_map(|resolved| cast_resolved(resolved, factory))
 }
 
 fn cast_origin<'a, Ctx: CastCtx<'a>, A: Mentionable<'a, Ctx>>(
-    typeless_origin: Rc<dyn Origin<'a, Ctx, Mtbl = TypelessMentionable<'a, Ctx>>>,
+    typeless_origin: Arc<dyn Origin<'a, Ctx, Mtbl = TypelessMentionable<'a, Ctx>>>,
     factory: A::Fctr,
-) -> Rc<dyn Origin<'a, Ctx, Mtbl = A>> {
+) -> Arc<dyn Origin<'a, Ctx, Mtbl = A>> {
     let origin_rb = typeless_origin.clone();
     wrapped_origin(
         factory.clone(),
@@ -209,7 +209,7 @@ impl<'a, Ctx: CastCtx<'a>> Point<'a, Ctx, TypelessMentionable<'a, Ctx>> {
     fn cast_origin<A: Mentionable<'a, Ctx>>(
         &self,
         factory: A::Fctr,
-    ) -> Rc<dyn Origin<'a, Ctx, Mtbl = A>> {
+    ) -> Arc<dyn Origin<'a, Ctx, Mtbl = A>> {
         let typeless_origin = self.origin.clone();
         cast_origin(typeless_origin, factory)
     }

src/rstd/collections/stack.rs

@@ -236,7 +236,7 @@ where
 
 #[cfg(test)]
 mod tests {
-    use std::rc::Rc;
+    use std::sync::Arc;
 
     use crate::rstd::{atomic::plain::*, atomic_object::*, tracing::*};
     use crate::testing::{counted::*, traced::*, *};
@@ -290,7 +290,7 @@ mod tests {
         let stack: T<TestContextCounted> = make_stack();
         let count = stack.clone().vec().count();
         assert_eq!(count, 0);
-        let stack: T<TestContextCounted> = Rc::new(stack).delay()?;
+        let stack: T<TestContextCounted> = Arc::new(stack).delay()?;
         let count = stack.clone().vec().count();
         assert_eq!(count, 3);
         Ok(())
@@ -303,7 +303,7 @@ mod tests {
         assert_eq!(traced.length(), 0);
         assert_eq!(traced.width(), 0);
         assert_eq!(format!("{}", traced.effect), ".");
-        let stack: T<TestContextTraced> = Rc::new(stack).trace()?;
+        let stack: T<TestContextTraced> = Arc::new(stack).trace()?;
         let traced = stack.clone().vec();
         assert_eq!(traced.length(), 3);
         assert_eq!(traced.width(), 1);
@@ -318,7 +318,7 @@ mod tests {
         assert_eq!(rendered.length(), 0);
         assert_eq!(rendered.width(), 0);
         assert_eq!(format!("{}", rendered), ".");
-        let stack: T<TestContextTraced> = Rc::new(stack).trace()?;
+        let stack: T<TestContextTraced> = Arc::new(stack).trace()?;
         let rendered = stack.clone().vec().render();
         assert_eq!(rendered.length(), 3);
         assert_eq!(rendered.width(), 1);

src/rstd/collections/tree/context.rs

@@ -1,4 +1,4 @@
-use std::{marker::PhantomData, rc::Rc};
+use std::{marker::PhantomData, sync::Arc};
 
 use crate::{
     flow::{
@@ -56,16 +56,26 @@ impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>, E: 'a> From<HeightError>
     }
 }
 
-pub type TreeContext2<'a, Ctx, A, C, E> = TreeContext<(Rc<C>, Fctr<'a, Ctx, A>), (Ctx, A, E)>;
+pub type TreeContext2<'a, Ctx, A, C, E> = TreeContext<(Arc<C>, Fctr<'a, Ctx, A>), (Ctx, A, E)>;
 
-impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx> + Clone, C: 'a + Comparator<A>, E: 'a>
-    FunctorContext<'a> for TreeContext2<'a, Ctx, A, C, E>
+impl<
+        'a,
+        Ctx: Context<'a>,
+        A: Mentionable<'a, Ctx> + Clone,
+        C: 'a + Comparator<A>,
+        E: 'a + Send,
+    > FunctorContext<'a> for TreeContext2<'a, Ctx, A, C, E>
 {
     type T = FallibleMonad<'a, Ctx, TreeContextError<'a, Ctx, A, E>>;
 }
 
-impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx> + Clone, C: 'a + Comparator<A>, E: 'a>
-    BinaryTrees<'a> for TreeContext2<'a, Ctx, A, C, E>
+impl<
+        'a,
+        Ctx: Context<'a>,
+        A: Mentionable<'a, Ctx> + Clone,
+        C: 'a + Comparator<A>,
+        E: 'a + Send,
+    > BinaryTrees<'a> for TreeContext2<'a, Ctx, A, C, E>
 {
     type Node = Node<'a, Ctx, A>;
 
@@ -107,8 +117,13 @@ impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx> + Clone, C: 'a + Comparator<A
     }
 }
 
-impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx> + Clone, C: 'a + Comparator<A>, E: 'a>
-    BinaryTreesEmpty<'a> for TreeContext2<'a, Ctx, A, C, E>
+impl<
+        'a,
+        Ctx: Context<'a>,
+        A: Mentionable<'a, Ctx> + Clone,
+        C: 'a + Comparator<A>,
+        E: 'a + Send,
+    > BinaryTreesEmpty<'a> for TreeContext2<'a, Ctx, A, C, E>
 {
     fn empty(&self) -> Self::Tree {
         Tree {
@@ -126,14 +141,19 @@ impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx> + Clone, C: 'a + Comparator<A
     }
 }
 
-impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx> + Clone, C: 'a + Comparator<A>, E: 'a>
-    BinaryTreesHeight<'a> for TreeContext2<'a, Ctx, A, C, E>
+impl<
+        'a,
+        Ctx: Context<'a>,
+        A: Mentionable<'a, Ctx> + Clone,
+        C: 'a + Comparator<A>,
+        E: 'a + Send,
+    > BinaryTreesHeight<'a> for TreeContext2<'a, Ctx, A, C, E>
 {
     fn height(&self, tree: &Self::Tree) -> u64 {
         tree.height
     }
 
-    fn height_error<T: 'a>(&self, error: HeightError) -> BTWrap<'a, Self, T> {
+    fn height_error<T: 'a + Send>(&self, error: HeightError) -> BTWrap<'a, Self, T> {
         Self::fail(error.into())
     }
 }
@@ -167,15 +187,20 @@ impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>, E: 'a> From<BoundsError<A>>
     }
 }
 
-impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx> + Clone, C: 'a + Comparator<A>, E: 'a>
-    BinaryTreesUnbalanced<'a> for TreeContext2<'a, Ctx, A, C, WrappedExtra<BalancingError, E>>
+impl<
+        'a,
+        Ctx: Context<'a>,
+        A: Mentionable<'a, Ctx> + Clone,
+        C: 'a + Comparator<A>,
+        E: 'a + Send,
+    > BinaryTreesUnbalanced<'a> for TreeContext2<'a, Ctx, A, C, WrappedExtra<BalancingError, E>>
 {
     fn tree_of_with_height(&self, node: Self::Node, height: u64) -> BTWrap<'a, Self, Self::Tree> {
         let node = Nullable::from(node);
         Self::pure(Tree { node, height })
     }
 
-    fn balancing_error<T: 'a>(&self, error: BalancingError) -> BTWrap<'a, Self, T> {
+    fn balancing_error<T: 'a + Send>(&self, error: BalancingError) -> BTWrap<'a, Self, T> {
         Self::fail(error.into())
     }
 
@@ -184,10 +209,15 @@ impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx> + Clone, C: 'a + Comparator<A
     }
 }
 
-impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx> + Clone, C: 'a + Comparator<A>, E: 'a>
-    BinaryTreesBindable<'a> for TreeContext2<'a, Ctx, A, C, WrappedExtra<BoundsError<A>, E>>
+impl<
+        'a,
+        Ctx: Context<'a>,
+        A: Mentionable<'a, Ctx> + Clone,
+        C: 'a + Comparator<A>,
+        E: 'a + Send,
+    > BinaryTreesBindable<'a> for TreeContext2<'a, Ctx, A, C, WrappedExtra<BoundsError<A>, E>>
 {
-    fn bounds_error<T: 'a>(&self, error: BoundsError<Self::Key>) -> BTWrap<'a, Self, T> {
+    fn bounds_error<T: 'a + Send>(&self, error: BoundsError<Self::Key>) -> BTWrap<'a, Self, T> {
         Self::fail(error.into())
     }
 }

src/rstd/inject.rs

@@ -1,13 +1,13 @@
-use std::rc::Rc;
+use std::sync::Arc;
 
 use crate::rcore::*;
 use crate::rstd::{singular::*, *};
 
-pub trait Inject<'a, Ctx: Context<'a>>: 'a + Sized {
-    fn inject<A: 'a>(&self, fa: Wrapped<'a, Ctx, A>) -> Wrapped<'a, Ctx, A>;
+pub trait Inject<'a, Ctx: Context<'a>>: 'a + Send + Sync + Sized {
+    fn inject<A: 'a + Send>(&self, fa: Wrapped<'a, Ctx, A>) -> Wrapped<'a, Ctx, A>;
 
     fn inject_mentionable<A: Mentionable<'a, Ctx>>(
-        self: Rc<Self>,
+        self: Arc<Self>,
         a: &A,
     ) -> ParseResultA<'a, Ctx, A> {
         let factory = a.factory();
@@ -20,12 +20,12 @@ pub trait Inject<'a, Ctx: Context<'a>>: 'a + Sized {
 }
 
 struct InjectedResolver<'a, Ctx: Context<'a>, F: Inject<'a, Ctx>> {
-    resolver: Rc<dyn Resolver<'a, Ctx>>,
-    inject: Rc<F>,
+    resolver: Arc<dyn Resolver<'a, Ctx>>,
+    inject: Arc<F>,
 }
 
 impl<'a, Ctx: Context<'a>, F: Inject<'a, Ctx>> Resolver<'a, Ctx> for InjectedResolver<'a, Ctx, F> {
-    fn resolve(self: Rc<Self>, address: Address) -> HashResolution<'a, Ctx> {
+    fn resolve(self: Arc<Self>, address: Address) -> HashResolution<'a, Ctx> {
         let inject = self.inject.clone();
         self.inject.inject(
             self.resolver

src/rstd/inlining/static_pair.rs

@@ -30,7 +30,7 @@ pub trait StaticPairSerializable {
 ///
 /// Note: [`StaticPair::FA`] requires [`InliningFactory`] be implemented.
 pub trait StaticPair<'a, Ctx: Context<'a>>:
-    'a + StaticPairSerializable<SA = Self::A, SB = Self::B> + Sized
+    'a + Send + Sync + StaticPairSerializable<SA = Self::A, SB = Self::B> + Sized
 {
     /// [Factory] data. May, depending on the usecase, include factory (factories) on the element(s).
     type FactoryData: 'a + Send + Sync + Clone;
@@ -43,7 +43,7 @@ pub trait StaticPair<'a, Ctx: Context<'a>>:
     /// Second element's factory.
     type FB: FactoryBase<'a, Ctx, Mtbl = Self::B> + ParseMode;
     /// See [`FactoryBase::ParseError`].
-    type ParseError: 'a + Error;
+    type ParseError: 'a + Send + Error;
 
     /// Borrow both elements' factories.
     fn factories(factory_data: &Self::FactoryData) -> (&Self::FA, &Self::FB);
@@ -266,7 +266,7 @@ pub trait StaticPairAtomic:
     /// Second element's type. Must equal [`StaticPairSerializable::SB`].
     type B: AtomicBase + ParseMode;
 
-    type AParseError: Error;
+    type AParseError: Error + Send;
     /// Construct the atomic from the elements.
     fn from_parsed(a: Self::A, b: Self::B) -> Result<Self, Self::AParseError>;
     /// Regularise the error returned while parsing the first element.

src/rstd/local_origin.rs

@@ -1,4 +1,4 @@
-use std::rc::Rc;
+use std::sync::Arc;
 
 use crate::func::context::*;
 use crate::rcore::*;
@@ -13,15 +13,15 @@ impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>> Point<'a, Ctx, A> {
         vec
     }
 
-    fn from_fields(point: Hash, origin: Rc<dyn Origin<'a, Ctx, Mtbl = A>>) -> Self {
+    fn from_fields(point: Hash, origin: Arc<dyn Origin<'a, Ctx, Mtbl = A>>) -> Self {
         Point { point, origin }
     }
 
     fn from_values<O: Origin<'a, Ctx, Mtbl = A>>(point: Hash, origin: O) -> Self {
-        Self::from_fields(point, Rc::new(origin))
+        Self::from_fields(point, Arc::new(origin))
     }
 
-    fn from_mentionable(mentionable: Rc<A>) -> Self {
+    fn from_mentionable(mentionable: Arc<A>) -> Self {
         Self::from_values(
             Ctx::hash(&Self::prepare_bytes_for_hashing(&mentionable)),
             LocalOrigin::from(mentionable),
@@ -29,7 +29,7 @@ impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>> Point<'a, Ctx, A> {
     }
 }
 
-struct LocalOrigin<A>(Rc<A>);
+struct LocalOrigin<A>(Arc<A>);
 
 impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>> Origin<'a, Ctx> for LocalOrigin<A> {
     type Mtbl = A;
@@ -38,26 +38,26 @@ impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>> Origin<'a, Ctx> for LocalOri
         self.0.factory()
     }
 
-    fn resolve(self: Rc<Self>) -> Resolution<'a, Ctx, Self::Mtbl> {
+    fn resolve(self: Arc<Self>) -> Resolution<'a, Ctx, Self::Mtbl> {
         Ctx::pure(Ok(self.0.clone()))
     }
 
-    fn resolve_bytes(self: Rc<Self>) -> HashResolution<'a, Ctx> {
+    fn resolve_bytes(self: Arc<Self>) -> HashResolution<'a, Ctx> {
         Ctx::pure(Ok((
             self.0.bytes(),
-            Rc::new(SingularResolver::from_mentionable(self.0.as_ref())),
+            Arc::new(SingularResolver::from_mentionable(self.0.as_ref())),
         )))
     }
 }
 
-impl<A> From<Rc<A>> for LocalOrigin<A> {
-    fn from(value: Rc<A>) -> Self {
+impl<A> From<Arc<A>> for LocalOrigin<A> {
+    fn from(value: Arc<A>) -> Self {
         LocalOrigin(value)
     }
 }
 
-impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>> From<Rc<A>> for Point<'a, Ctx, A> {
-    fn from(value: Rc<A>) -> Self {
+impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>> From<Arc<A>> for Point<'a, Ctx, A> {
+    fn from(value: Arc<A>) -> Self {
         Self::from_mentionable(value)
     }
 }

src/rstd/nullable.rs

@@ -73,7 +73,7 @@ impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>> Nullable<'a, Ctx, Nullable<'
         match self {
             Self::Null(nullable_factory) => {
                 let NullableFactory { factory } = nullable_factory;
-                Ctx::pure(Ok(Rc::new(Nullable::Null(factory.clone()))))
+                Ctx::pure(Ok(Arc::new(Nullable::Null(factory.clone()))))
             }
             Self::NotNull(point) => point.resolve(),
         }
@@ -81,7 +81,7 @@ impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>> Nullable<'a, Ctx, Nullable<'
 }
 
 impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>> Nullable<'a, Ctx, A> {
-    fn from_mentionable(mentionable: Rc<A>) -> Self {
+    fn from_mentionable(mentionable: Arc<A>) -> Self {
         Self::NotNull(mentionable.into())
     }
 
@@ -142,8 +142,8 @@ impl<F> AlwaysConstSize for NullableFactory<F> {
     const _SIZE: usize = HASH_SIZE;
 }
 
-impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>> From<Rc<A>> for Nullable<'a, Ctx, A> {
-    fn from(value: Rc<A>) -> Self {
+impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>> From<Arc<A>> for Nullable<'a, Ctx, A> {
+    fn from(value: Arc<A>) -> Self {
         Self::from_mentionable(value)
     }
 }

src/rstd/singular.rs

@@ -1,8 +1,9 @@
 use crate::rcore::*;
-use crate::rstd::*;
 
-trait SingularResolution<'a, Ctx: Context<'a>>: 'a {
-    fn singular(self: Rc<Self>) -> HashResolution<'a, Ctx>;
+use super::*;
+
+trait SingularResolution<'a, Ctx: Context<'a>>: 'a + Send + Sync {
+    fn singular(self: Arc<Self>) -> HashResolution<'a, Ctx>;
 
     fn s_hash(&self) -> Hash;
 }
@@ -10,7 +11,7 @@ trait SingularResolution<'a, Ctx: Context<'a>>: 'a {
 impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>> SingularResolution<'a, Ctx>
     for Point<'a, Ctx, A>
 {
-    fn singular(self: Rc<Self>) -> HashResolution<'a, Ctx> {
+    fn singular(self: Arc<Self>) -> HashResolution<'a, Ctx> {
         self.origin.clone().resolve_bytes()
     }
 
@@ -20,7 +21,7 @@ impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>> SingularResolution<'a, Ctx>
 }
 
 pub struct SingularResolver<'a, Ctx: Context<'a>> {
-    points: Vec<Rc<dyn SingularResolution<'a, Ctx>>>,
+    points: Vec<Arc<dyn SingularResolution<'a, Ctx>>>,
 }
 
 impl<'a, Ctx: Context<'a>> SingularResolver<'a, Ctx> {
@@ -32,7 +33,7 @@ impl<'a, Ctx: Context<'a>> SingularResolver<'a, Ctx> {
 }
 
 impl<'a, Ctx: Context<'a>> Resolver<'a, Ctx> for SingularResolver<'a, Ctx> {
-    fn resolve(self: Rc<Self>, address: Address) -> HashResolution<'a, Ctx> {
+    fn resolve(self: Arc<Self>, address: Address) -> HashResolution<'a, Ctx> {
         let point = self.points.get(address.index).unwrap_or_else(|| {
             panic!(
                 "singularity out-of-bounds: {}/{}",
@@ -52,8 +53,8 @@ impl<'a, Ctx: Context<'a>> Resolver<'a, Ctx> for SingularResolver<'a, Ctx> {
     }
 }
 
-impl<'a, Ctx: Context<'a>> PointsVisitor<'a, Ctx> for Vec<Rc<dyn SingularResolution<'a, Ctx>>> {
+impl<'a, Ctx: Context<'a>> PointsVisitor<'a, Ctx> for Vec<Arc<dyn SingularResolution<'a, Ctx>>> {
     fn visit<A: Mentionable<'a, Ctx>>(&mut self, point: &Point<'a, Ctx, A>) {
-        self.push(Rc::new(point.clone()) as _);
+        self.push(Arc::new(point.clone()) as _);
     }
 }

src/rstd/tracing/traceable.rs

@@ -5,7 +5,7 @@ use super::*;
 struct TracedInject;
 
 impl<'a, Ctx: Context<'a, _Tm = TracedInstance>> Inject<'a, Ctx> for TracedInject {
-    fn inject<A: 'a>(&self, fa: Wrapped<'a, Ctx, A>) -> Wrapped<'a, Ctx, A> {
+    fn inject<A: 'a + Send>(&self, fa: Wrapped<'a, Ctx, A>) -> Wrapped<'a, Ctx, A> {
         fa.after_resolution()
     }
 }
@@ -20,7 +20,7 @@ pub trait Traceable<'a, Ctx: Context<'a, _Tm = TracedInstance>>:
     /// [^extra]: applying [`Traceable::trace`] multiple times
     /// might affect the trace in undesireable ways
     fn trace(&self) -> ParseResultA<'a, Ctx, Self> {
-        Rc::new(TracedInject).inject_mentionable(self)
+        Arc::new(TracedInject).inject_mentionable(self)
     }
 }
 

src/rstd/typeless.rs

@@ -5,7 +5,7 @@
 use super::{cast::*, wrapped_origin::*, *};
 use crate::mode::*;
 
-type TypelessSerialize<'a> = dyn 'a + Fn(&mut dyn Serializer);
+type TypelessSerialize<'a> = dyn 'a + Send + Sync + Fn(&mut dyn Serializer);
 
 /// See [`Point::typeless`].
 pub struct TypelessMentionable<'a, Ctx: Context<'a>> {
@@ -15,7 +15,7 @@ pub struct TypelessMentionable<'a, Ctx: Context<'a>> {
     t_points: Vec<Point<'a, Ctx, TypelessMentionable<'a, Ctx>>>,
 }
 
-type TypelessParsed<'a, Ctx> = Result<TypelessMentionable<'a, Ctx>, Box<dyn 'a + Error>>;
+type TypelessParsed<'a, Ctx> = Result<TypelessMentionable<'a, Ctx>, Box<dyn 'a + Send + Error>>;
 
 trait Tde<'a, Ctx: Context<'a>>: 'a + Send + Sync {
     fn clone_box(&self) -> TdeBox<'a, Ctx>;
@@ -82,7 +82,7 @@ impl<'a, Ctx: Context<'a>> Clone for TypelessFactory<'a, Ctx> {
 
 /// See [`Point::typeless`]/[`TypelessFactory`].
 #[derive(Debug)]
-pub struct TypelessError<'a>(Box<dyn 'a + Error>);
+pub struct TypelessError<'a>(Box<dyn 'a + Send + Error>);
 
 impl<'a> Display for TypelessError<'a> {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
@@ -113,7 +113,7 @@ impl<'a, Ctx: Context<'a>> CRegularFactory<'a, Ctx> for TypelessFactory<'a, Ctx>
 }
 
 impl<'a, Ctx: CastCtx<'a>> TypelessMentionable<'a, Ctx> {
-    pub fn from_typed<A: Mentionable<'a, Ctx>>(mentionable: Rc<A>) -> Self {
+    pub fn from_typed<A: Mentionable<'a, Ctx>>(mentionable: Arc<A>) -> Self {
         let factory = TypelessFactory::from_typed(mentionable.factory());
         let topology = mentionable.topology();
         let points = mentionable.points_vec();
@@ -137,7 +137,7 @@ impl<'a, Ctx: CastCtx<'a>, F: Factory<'a, Ctx>> Tde<'a, Ctx> for F {
     {
         self.deserialize(demoted)
             .map_err(|e| Box::new(e) as _)
-            .map(Rc::new)
+            .map(Arc::new)
             .map(TypelessMentionable::from_typed)
     }
 }
@@ -160,7 +160,7 @@ impl<'a, Ctx: CastCtx<'a>, F: Factory<'a, Ctx>> Tut<'a, Ctx> for F {
             tail,
         )
         .map_err(TypelessError::from_typed)
-        .map(Rc::new)
+        .map(Arc::new)
         .map(TypelessMentionable::from_typed)
     }
 }
@@ -175,7 +175,7 @@ impl<'a, Ctx: CastCtx<'a>> TypelessFactory<'a, Ctx> {
 }
 
 impl<'a> TypelessError<'a> {
-    pub fn from_typed<E: 'a + Error>(error: E) -> Self {
+    pub fn from_typed<E: 'a + Send + Error>(error: E) -> Self {
         TypelessError(Box::new(error))
     }
 }

src/rstd/wrapped_origin.rs

@@ -4,10 +4,10 @@ use super::*;
 
 pub fn wrapped_origin<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>>(
     factory: A::Fctr,
-    resolve: impl 'a + Fn() -> Resolution<'a, Ctx, A>,
-    resolve_bytes: impl 'a + Fn() -> HashResolution<'a, Ctx>,
-) -> Rc<dyn Origin<'a, Ctx, Mtbl = A>> {
-    Rc::new(WrappedOrigin {
+    resolve: impl 'a + Send + Sync + Fn() -> Resolution<'a, Ctx, A>,
+    resolve_bytes: impl 'a + Send + Sync + Fn() -> HashResolution<'a, Ctx>,
+) -> Arc<dyn Origin<'a, Ctx, Mtbl = A>> {
+    Arc::new(WrappedOrigin {
         w_factory: factory,
         w_resolve: Box::new(resolve),
         w_resolve_bytes: Box::new(resolve_bytes),
@@ -16,15 +16,15 @@ pub fn wrapped_origin<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>>(
 
 pub trait MappableOrigin<'a, Ctx: Context<'a>>: Origin<'a, Ctx> {
     fn map<B: Mentionable<'a, Ctx>>(
-        self: Rc<Self>,
-        map_ok: impl 'a + Send + Sync + Clone + Fn(Rc<Self::Mtbl>) -> B,
+        self: Arc<Self>,
+        map_ok: impl 'a + Send + Sync + Clone + Fn(Arc<Self::Mtbl>) -> B,
         map_err: impl 'a
             + Send
             + Sync
             + Clone
             + Fn(ParseError<'a, Ctx, OFctr<'a, Ctx, Self>>) -> ParseError<'a, Ctx, B::Fctr>,
         map_factory: impl 'a + FnOnce(OFctr<'a, Ctx, Self>) -> B::Fctr,
-    ) -> Rc<dyn Origin<'a, Ctx, Mtbl = B>>
+    ) -> Arc<dyn Origin<'a, Ctx, Mtbl = B>>
     where
         OFctr<'a, Ctx, Self>: Factory<'a, Ctx, _Mtbl = Self::Mtbl>,
         Self::Mtbl: MentionableTop<'a, Ctx>,
@@ -41,27 +41,27 @@ pub trait MappableOrigin<'a, Ctx: Context<'a>>: Origin<'a, Ctx> {
             }),
             w_resolve_bytes: Box::new(move || origin_rb.clone().resolve_bytes()),
         };
-        Rc::new(origin)
+        Arc::new(origin)
     }
 }
 
 impl<'a, Ctx: Context<'a>, O: ?Sized + Origin<'a, Ctx>> MappableOrigin<'a, Ctx> for O {}
 
 fn map_resolve<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>, B: Mentionable<'a, Ctx>>(
-    resolve: impl 'a + Fn() -> Resolution<'a, Ctx, A>,
-    map_ok: impl 'a + Fn(Rc<A>) -> B,
-    map_err: impl 'a + Fn(ParseError<'a, Ctx, A::Fctr>) -> ParseError<'a, Ctx, B::Fctr>,
+    resolve: impl 'a + Send + Fn() -> Resolution<'a, Ctx, A>,
+    map_ok: impl 'a + Send + Fn(Arc<A>) -> B,
+    map_err: impl 'a + Send + Fn(ParseError<'a, Ctx, A::Fctr>) -> ParseError<'a, Ctx, B::Fctr>,
 ) -> Resolution<'a, Ctx, B> {
     Ctx::fmap(resolve(), move |resolved| match resolved {
-        Ok(mentionable) => Ok(Rc::new(map_ok(mentionable))),
+        Ok(mentionable) => Ok(Arc::new(map_ok(mentionable))),
         Err(e) => Err(e.map_parse(map_err)),
     })
 }
 
 struct WrappedOrigin<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>> {
     w_factory: A::Fctr,
-    w_resolve: Box<dyn 'a + Fn() -> Resolution<'a, Ctx, A>>,
-    w_resolve_bytes: Box<dyn 'a + Fn() -> HashResolution<'a, Ctx>>,
+    w_resolve: Box<dyn 'a + Send + Sync + Fn() -> Resolution<'a, Ctx, A>>,
+    w_resolve_bytes: Box<dyn 'a + Send + Sync + Fn() -> HashResolution<'a, Ctx>>,
 }
 
 impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>> Origin<'a, Ctx> for WrappedOrigin<'a, Ctx, A> {
@@ -71,11 +71,11 @@ impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>> Origin<'a, Ctx> for WrappedO
         self.w_factory.clone()
     }
 
-    fn resolve(self: Rc<Self>) -> Resolution<'a, Ctx, A> {
+    fn resolve(self: Arc<Self>) -> Resolution<'a, Ctx, A> {
         (self.w_resolve)()
     }
 
-    fn resolve_bytes(self: Rc<Self>) -> HashResolution<'a, Ctx> {
+    fn resolve_bytes(self: Arc<Self>) -> HashResolution<'a, Ctx> {
         (self.w_resolve_bytes)()
     }
 }

src/testing.rs

@@ -1,7 +1,7 @@
 pub mod counted;
 pub mod traced;
 
-use std::{error::Error, fmt::Display, rc::Rc};
+use std::{error::Error, fmt::Display, sync::Arc};
 
 use sha2::{Digest, Sha256};
 
@@ -12,15 +12,15 @@ use crate::rstd::{cast::*, inject::*, typeless::*};
 pub struct NoDiagnostic;
 
 impl<'a, T: Monad<'a>> Diagnostic<'a, T> for NoDiagnostic {
-    fn after<'b, A>(fa: T::F<A>, _event: impl 'b + FnOnce() -> String) -> T::F<A> {
+    fn after<'b, A: 'a + Send>(fa: T::F<A>, _event: impl 'b + FnOnce() -> String) -> T::F<A> {
         fa
     }
 
-    fn before<'b, A>(fa: T::F<A>, _event: impl 'b + FnOnce() -> String) -> T::F<A> {
+    fn before<'b, A: 'a + Send>(fa: T::F<A>, _event: impl 'b + FnOnce() -> String) -> T::F<A> {
         fa
     }
 
-    fn wrapped<'b, A>(fa: T::F<A>, _event: impl 'b + FnOnce() -> String) -> T::F<A> {
+    fn wrapped<'b, A: 'a + Send>(fa: T::F<A>, _event: impl 'b + FnOnce() -> String) -> T::F<A> {
         fa
     }
 }
@@ -89,7 +89,7 @@ impl<'a> Context<'a> for TestContextPlain {
 pub struct EmptyResolver;
 
 impl<'a> Resolver<'a, TestContextPlain> for EmptyResolver {
-    fn resolve(self: std::rc::Rc<Self>, address: Address) -> HashResolution<'a, TestContextPlain> {
+    fn resolve(self: Arc<Self>, address: Address) -> HashResolution<'a, TestContextPlain> {
         Err(TestLookupError::EmptyResolverAccess(address))
     }
 }
@@ -97,13 +97,13 @@ impl<'a> Resolver<'a, TestContextPlain> for EmptyResolver {
 struct EmptyInject;
 
 impl<'a, Ctx: Context<'a>> Inject<'a, Ctx> for EmptyInject {
-    fn inject<A: 'a>(&self, fa: Wrapped<'a, Ctx, A>) -> Wrapped<'a, Ctx, A> {
+    fn inject<A: 'a + Send>(&self, fa: Wrapped<'a, Ctx, A>) -> Wrapped<'a, Ctx, A> {
         fa
     }
 }
 
-pub fn reparse<'a, A: Mentionable<'a, TestContextPlain>>(mentionable: Rc<A>) -> A {
-    Rc::new(EmptyInject)
+pub fn reparse<'a, A: Mentionable<'a, TestContextPlain>>(mentionable: Arc<A>) -> A {
+    Arc::new(EmptyInject)
         .inject_mentionable(mentionable.as_ref())
         .expect("re-parsing failed")
 }

src/testing/counted.rs

@@ -61,7 +61,7 @@ impl<A> Counted<A> {
 struct CountedInject;
 
 impl<'a> Inject<'a, TestContextCounted> for CountedInject {
-    fn inject<A: 'a>(
+    fn inject<A: 'a + Send>(
         &self,
         fa: Wrapped<'a, TestContextCounted, A>,
     ) -> Wrapped<'a, TestContextCounted, A> {
@@ -71,7 +71,7 @@ impl<'a> Inject<'a, TestContextCounted> for CountedInject {
 
 pub trait Delayable<'a>: Mentionable<'a, TestContextCounted> + Sized {
     fn delay(&self) -> ParseResultA<'a, TestContextCounted, Self> {
-        Rc::new(CountedInject).inject_mentionable(self)
+        Arc::new(CountedInject).inject_mentionable(self)
     }
 }