Trigger execution of flattened delayed futures

fix #611

Author: pitr-ch

lib/concurrent/edge/future.rb

@@ -1180,6 +1180,7 @@ def process_on_done(future)
           value = internal_state.value
           case value
           when Future
+            value.touch if self.future.touched
             @BlockedBy.push value
             value.add_callback :callback_notify_blocked, self
             @Countdown.value

spec/concurrent/edge/future_spec.rb

@@ -378,6 +378,10 @@
         f = Concurrent.future { Concurrent.completed_event }.flat
         expect(f.reason).to be_an_instance_of TypeError
       end
+
+      it 'propagates requests for values to delayed futures' do
+        expect(Concurrent.future { Concurrent.delay { 1 } }.flat.value!(0.1)).to eq 1
+      end
     end
 
     it 'completes future when Exception raised' do