ActiveSupport::Delegation optimize self.class delegation

Since `self.class` can't possible be `nil`, we can skip the
useless `nil` checks and generate more efficient code.

Author: byroot

activesupport/lib/active_support/current_attributes.rb

@@ -132,7 +132,7 @@ def attribute(*names, default: nil)
           end
         end
 
-        Delegation.generate(singleton_class, names.flat_map { |name| [name, "#{name}="] }, to: :instance, as: self)
+        Delegation.generate(singleton_class, names.flat_map { |name| [name, "#{name}="] }, to: :instance, as: self, nilable: false)
 
         self.defaults = defaults.merge(names.index_with { default })
       end
@@ -184,7 +184,7 @@ def method_added(name)
           return if name == :initialize
           return unless public_method_defined?(name)
           return if respond_to?(name, true)
-          Delegation.generate(singleton_class, [name], to: :instance, as: self)
+          Delegation.generate(singleton_class, [name], to: :instance, as: self, nilable: false)
         end
     end
 

activesupport/lib/active_support/delegation.rb

@@ -20,7 +20,7 @@ module Delegation # :nodoc:
     RESERVED_METHOD_NAMES = (RUBY_RESERVED_KEYWORDS + %w(_ arg args block)).to_set.freeze
 
     class << self
-      def generate(owner, methods, location: nil, to: nil, prefix: nil, allow_nil: nil, private: nil, as: nil)
+      def generate(owner, methods, location: nil, to: nil, prefix: nil, allow_nil: nil, nilable: true, private: nil, as: nil)
         unless to
           raise ArgumentError, "Delegation needs a target. Supply a keyword argument 'to' (e.g. delegate :hello, to: :greeter)."
         end
@@ -49,6 +49,7 @@ def generate(owner, methods, location: nil, to: nil, prefix: nil, allow_nil: nil
         elsif to.is_a?(Module)
           to.singleton_class
         elsif receiver == "self.class"
+          nilable = false # self.class can't possibly be nil
           owner.singleton_class
         end
 
@@ -98,7 +99,12 @@ def generate(owner, methods, location: nil, to: nil, prefix: nil, allow_nil: nil
           # On the other hand it could be that the target has side-effects,
           # whereas conceptually, from the user point of view, the delegator should
           # be doing one call.
-          if allow_nil
+          if nilable == false
+            method_def <<
+              "def #{method_name}(#{definition})" <<
+              "  (#{receiver}).#{method}(#{definition})" <<
+              "end"
+          elsif allow_nil
             method = method.to_s
 
             method_def <<

activesupport/lib/active_support/duration.rb

@@ -221,7 +221,7 @@ def calculate_total_seconds(parts)
         end
     end
 
-    Delegation.generate(self, [:to_f, :positive?, :negative?, :zero?, :abs], to: :@value, as: Integer)
+    Delegation.generate(self, [:to_f, :positive?, :negative?, :zero?, :abs], to: :@value, as: Integer, nilable: false)
 
     def initialize(value, parts, variable = nil) # :nodoc:
       @value, @parts = value, parts