Minor refactoring and doc updates.

Author: jdantonio

lib/concurrent/delay.rb

@@ -60,7 +60,7 @@ class Delay < Synchronization::Object
     def initialize(opts = {}, &block)
       raise ArgumentError.new('no block given') unless block_given?
 
-      super(&nil)
+      super()
       init_obligation(self)
       set_deref_options(opts)
       @task_executor = get_executor_from(opts)

lib/concurrent/dereferenceable.rb

@@ -47,7 +47,7 @@ def value
 
     # Set the internal value of this object
     #
-    # @param [Object] val the new value
+    # @param [Object] value the new value
     def value=(value)
       mutex.synchronize{ @value = value }
     end

lib/concurrent/ivar.rb

@@ -100,9 +100,13 @@ def add_observer(observer = nil, func = :update, &block)
 
     # Set the `IVar` to a value and wake or notify all threads waiting on it.
     #
-    # @param [Object] value the value to store in the `IVar`
-    # @raise [Concurrent::MultipleAssignmentError] if the `IVar` has already
-    #   been set or otherwise completed
+    # @!macro [attach] ivar_set_parameters_and_exceptions
+    #   @param [Object] value the value to store in the `IVar`
+    #   @yield A block operation to use for setting the value
+    #   @raise [ArgumentError] if both a value and a block are given
+    #   @raise [Concurrent::MultipleAssignmentError] if the `IVar` has already
+    #     been set or otherwise completed
+    #
     # @return [IVar] self
     def set(value = NO_VALUE)
       check_for_block_or_value!(block_given?, value)
@@ -123,9 +127,15 @@ def set(value = NO_VALUE)
     #   been set or otherwise completed
     # @return [IVar] self
     def fail(reason = StandardError.new)
-      set { raise reason }
+      complete(false, nil, reason)
     end
 
+    # Attempt to set the `IVar` with the given value or block. Return a
+    # boolean indicating the success or failure of the set operation.
+    #
+    # @!macro ivar_set_parameters_and_exceptions
+    #
+    # @return [Boolean] true if the value was set else false
     def set?(value = NO_VALUE, &block)
       set(value, &block)
       true

lib/concurrent/promise.rb

@@ -253,6 +253,10 @@ def set(value = IVar::NO_VALUE, &block)
       execute
     end
 
+    def fail(reason = StandardError.new)
+      set { raise reason }
+    end
+
     # Create a new `Promise` object with the given block, execute it, and return the
     # `:pending` object.
     #

lib/concurrent/synchronization/abstract_object.rb

@@ -7,7 +7,9 @@ module Synchronization
     # Provides a single layer which can improve its implementation over time without changes needed to
     # the classes using it. Use {Synchronization::Object} not this abstract class.
     #
-    # @note this object does not support usage together with {Thread#wakeup} and {Thread#raise}.
+    # @note this object does not support usage together with
+    #   [Thread#wakeup](http://ruby-doc.org/core-2.2.0/Thread.html#method-i-wakeup)
+    #   and [Thread#raise](http://ruby-doc.org/core-2.2.0/Thread.html#method-i-raise).
     #   `Thread#sleep` and `Thread#wakeup` will work as expected but mixing `Synchronization::Object#wait` and
     #   `Thread#wakeup` will not work on all platforms.
     #