Update for Ruby 2.7 compatibility

Author: zverok

.travis.yml

@@ -5,6 +5,7 @@ rvm:
   - "2.4.0"
   - "2.5.0"
   - "2.6.0"
+  - ruby-head
   - jruby-9.2.5.0
 matrix:
   allow_failures:

lib/time_calc.rb

@@ -274,8 +274,9 @@ def ==(other)
   OPERATIONS = MATH_OPERATIONS.+(%i[to step for]).freeze
 
   OPERATIONS.each do |name|
-    define_method(name) { |*args, &block|
-      @value.public_send(name, *args, &block).then { |res| res.is_a?(Value) ? res.unwrap : res }
+    define_method(name) { |*args, **kwargs, &block|
+      @value.public_send(name, *args, **kwargs, &block)
+            .then { |res| res.is_a?(Value) ? res.unwrap : res }
     }
   end
 

lib/time_calc/diff.rb

@@ -285,7 +285,7 @@ def coerce_zones(from, to)
     # Will coerce Date to Time or DateTime, with the _zone of the latter_
     def coerce_date(date, other)
       TimeCalc.(other)
-        .merge(Units::DEFAULTS.merge(year: date.year, month: date.month, day: date.day))
+        .merge(**Units::DEFAULTS.merge(year: date.year, month: date.month, day: date.day))
     end
   end
 end

lib/time_calc/value.rb

@@ -7,20 +7,22 @@
 require 'backports/2.5.0/hash/slice'
 require 'backports/2.5.0/enumerable/all'
 
-# @private
-# TODO: It is included in Ruby 2.7. Replace with backports when it will be there.
-class Enumerator
-  NOVALUE = Object.new.freeze
-
-  def self.produce(initial = NOVALUE)
-    fail ArgumentError, 'No block given' unless block_given?
-
-    Enumerator.new do |y|
-      val = initial == NOVALUE ? yield() : initial
-
-      loop do
-        y << val
-        val = yield(val)
+if RUBY_VERSION < '2.7'
+  # @private
+  # TODO: Replace with backports after 2.7 release
+  class Enumerator
+    NOVALUE = Object.new.freeze
+
+    def self.produce(initial = NOVALUE)
+      fail ArgumentError, 'No block given' unless block_given?
+
+      Enumerator.new do |y|
+        val = initial == NOVALUE ? yield() : initial
+
+        loop do
+          y << val
+          val = yield(val)
+        end
       end
     end
   end
@@ -118,7 +120,7 @@ def truncate(unit)
         .drop_while { |u| u != unit }
         .drop(1)
         .then { |keys| Units::DEFAULTS.slice(*keys) }
-        .then(&method(:merge))
+        .then { |attrs| merge(**attrs) } # can't simplify to &method(:merge) due to 2.7 keyword param problem
     end
 
     alias floor truncate