Merge pull request #2006 from ParadoxV5/2004-enum-each

Use generic class definitions with default types in `top`/`Enumerator``::_Each`

Author: soutaro

core/builtin.rbs

@@ -170,12 +170,12 @@ interface _Inspect
   def inspect: () -> String
 end
 
-interface _Each[out A]
-  def each: () { (A) -> void } -> void
+interface _Each[out E, out R = void]
+  def each: () { (E) -> void } -> R
 end
 
-interface _EachEntry[out A]
-  def each_entry: () { (A) -> void } -> self
+interface _EachEntry[out E]
+  def each_entry: () { (E) -> void } -> self
 end
 
 interface _Reader

core/enumerator.rbs

@@ -132,7 +132,7 @@ class Enumerator[unchecked out Elem, out Return = void] < Object
 
   # A convenience interface for `each` with optional block
   #
-  interface _Each[out E, out R]
+  interface _Each[out E, out R = self]
     def each: () { (E) -> void } -> R
             | () -> Enumerator[E, R]
   end