Data commit

Task/Constrained-genericity/Crystal/constrained-genericity.crystal

@@ -0,0 +1,23 @@
+class Apple
+  def eat
+  end
+end
+
+class Carrot
+  def eat
+  end
+end
+
+class FoodBox(T)
+  def initialize(@data : Array(T))
+    {% if T.union? %}
+    {% raise "All items should be eatable" unless T.union_types.all? &.has_method?(:eat) %}
+    {% else %}
+    {% raise "Items should be eatable" unless T.has_method?(:eat) %}
+    {% end %}
+  end
+end
+
+FoodBox.new([Apple.new, Apple.new])
+FoodBox.new([Apple.new, Carrot.new])
+FoodBox.new([Apple.new, Carrot.new, 123])