Normalize :: syntax (#5048)

* normalize :: syntax

* fixes from code review

test/formatting.coffee

@@ -70,6 +70,12 @@ test "`?.` and `::` should continue lines", ->
     ::
     ?.foo
   )
+
+  ok not (
+    Date
+    ?::
+    ?.foo
+  )
   #eq Object::toString, Date?.
   #prototype
   #::

test/operators.coffee

@@ -303,7 +303,16 @@ test "#2567: Optimization of negated existential produces correct result", ->
 
 test "#2508: Existential access of the prototype", ->
   eq NonExistent?::nothing, undefined
+  eq(
+    NonExistent
+    ?::nothing
+    undefined
+  )
   ok Object?::toString
+  ok(
+    Object
+    ?::toString
+  )
 
 test "floor division operator", ->
   eq 2, 7 // 3