void_can_be_exressed_via_replace

src/func/test_suite.rs

@@ -75,5 +75,8 @@ pub fn monad_follows_laws<'a, T: Monad<'a> + FunctorTestSuite<'a>>() -> R {
     T::sample(|pa| {
         res += fmap_can_be_expressed_via_bind::<T, _, _>(|x| x + 3, || pa(2));
     });
+    T::sample(|pa| {
+        res += void_can_be_exressed_via_replace::<T, _>(|| pa(2));
+    });
     res
 }

src/func/tests.rs

@@ -317,3 +317,17 @@ pub fn fmap_can_be_expressed_via_bind<
         T::bind(fa0(), move |a| T::pure(f(a))),
     )
 }
+
+pub fn void_can_be_exressed_via_replace<
+    'a,
+    T: Monad<'a> + Eqr<'a>,
+    A: 'a + Send + Debug + PartialEq,
+>(
+    fa0: impl Fn() -> T::F<A>,
+) -> R {
+    T::eqr(
+        "void via bind: void x  =  () <$ x",
+        T::void(fa0()),
+        T::replace(fa0(), ()),
+    )
+}