select_of_equal_is_same

src/func/test_suite.rs

@@ -57,6 +57,9 @@ pub fn applicative_follows_laws<'a, T: Applicative<'a> + FunctorTestSuite<'a>>()
             res += tuple_can_be_expressed_via_la2::<T, _, _>(|| pa(2), || pb(2));
         })
     });
+    T::sample(|pa| {
+        res += select_of_equal_is_same::<T, _>(|| pa(2));
+    });
     res
 }
 

src/func/tests.rs

@@ -3,6 +3,7 @@ use std::{
     ops::{Add, AddAssign},
 };
 
+use applicative_select::Selected;
 use controlflow::IterativeWrapped;
 
 use super::*;
@@ -400,3 +401,19 @@ pub fn iterate_can_be_expressed_via_bind<
         T::bind(fa0(), f0()),
     )
 }
+
+pub fn select_of_equal_is_same<
+    'a,
+    T: Applicative<'a> + Eqr<'a>,
+    A: 'a + Send + Debug + PartialEq,
+>(
+    fa0: impl 'a + Fn() -> T::F<A>,
+) -> R {
+    T::eqr(
+        "select of equal",
+        T::fmap(T::select(fa0(), fa0()), |selected| match selected {
+            Selected::A(a, _) | Selected::B(_, a) => a,
+        }),
+        fa0(),
+    )
+}