Tentatively accept anything as a proc type

lib/typeprof/core/ast/sig_type.rb

@@ -590,7 +590,7 @@ def covariant_vertex0(genv, changes, vtx, subst)
       end
 
       def contravariant_vertex0(genv, changes, vtx, subst)
-        raise NotImplementedError
+        Source.new()
       end
 
       def show

scenario/misc/proc.rb

@@ -0,0 +1,15 @@
+## update: test.rbs
+class Object
+  def foo: (^(Integer) -> void) -> void
+end
+
+## update: test.rb
+def check(x)
+end
+f = ->(x) { check(x) } # TODO: this should pass an Integer to the method "check"? Is it possible?
+foo(f)
+
+## assert
+class Object
+  def check: (untyped) -> nil
+end