Allow non-Function callables to be used in count(f, itr) (#36187)

Author: tkf

base/reduce.jl

@@ -840,7 +840,7 @@ end
 
 ## count
 
-_bool(f::Function) = x->f(x)::Bool
+_bool(f) = x->f(x)::Bool
 
 """
     count(p, itr) -> Integer

test/reduce.jl

@@ -480,6 +480,11 @@ end
 @test count(!iszero, Int[1]) == 1
 @test count(!iszero, [1, 0, 2, 0, 3, 0, 4]) == 4
 
+struct NonFunctionIsZero end
+(::NonFunctionIsZero)(x) = iszero(x)
+@test count(NonFunctionIsZero(), []) == 0
+@test count(NonFunctionIsZero(), [0]) == 1
+@test count(NonFunctionIsZero(), [1]) == 0
 
 ## cumsum, cummin, cummax