fixup: select can check if any op is ready before spawning fibers

src/channel.cr

@@ -107,10 +107,20 @@ abstract class Channel(T)
   # execution so the *fibers* array will always be filled with all fibers, so
   # any ready operation can cancel all other fibers ASAP.
   def self.select(ops : Tuple | Array, has_else = false)
+    # fast path: check if any clause is ready
+    ops.each_with_index do |op, i|
+      if op.ready?
+        return {i, op.execute}
+      end
+    end
+
+    if has_else
+      return {ops.size, nil}
+    end
+
+    # slow path: spawn fibers to wait on each clause
     main = Fiber.current
     fibers = Array(Fiber).new(ops.size)
-
-    waiting = 0
     index = -1
     value = nil
 
@@ -128,13 +138,6 @@ abstract class Channel(T)
             break
           end
 
-          if has_else && (waiting += 1) == ops.size
-            cancel_select_actions(ops, fibers, i)
-            index = ops.size
-            Crystal::Scheduler.enqueue(main)
-            break
-          end
-
           op.wait
           Crystal::Scheduler.reschedule
         end