Ensure keyword arguments for Concurrent::*Struct behave similarly to …

…Std-lib Struct

lib/concurrent/synchronization/abstract_struct.rb

@@ -142,8 +142,14 @@ def self.define_struct_class(parent, base, name, members, kw_args, &block)
           self.const_set(:MEMBERS, members.collect{|member| member.to_s.to_sym}.freeze)
           self.const_set(:KEYWORD_INIT, !!kw_args[:keyword_init])
           def ns_initialize(*values, **kw_values)
-            raise ArgumentError.new('struct size differs') if values.length > length || kw_values.length > length
-            @values = keyword_init? ? members.map{ |val| kw_values.fetch(val, nil) } : values.fill(nil, values.length..length-1)
+            @values = if keyword_init?
+              key_diff = kw_values.keys - members
+              raise ArgumentError.new("unknown keywords: #{key_diff.join(',')}") unless key_diff.empty?
+              members.map {|val| kw_values.fetch(val, nil)}
+            else
+              raise ArgumentError.new('struct size differs') if values.length > length
+              values.fill(nil, values.length..length-1)
+            end
           end
         end
         unless name.nil?

spec/concurrent/struct_shared.rb

@@ -101,8 +101,13 @@ def baz(foo, bar) foo + bar; end
 
     it 'raises an exception when extra members are given' do
       classes.each do |clazz|
-        extra_values = values << 'forty two'
-        expect{ clazz.new(*extra_values) }.to raise_error(ArgumentError)
+        if clazz::KEYWORD_INIT
+          extra_values = kw_values.merge({FortyTwo: 'forty two'})
+          expect{ clazz.new(**extra_values) }.to raise_error(ArgumentError)
+        else  
+          extra_values = values << 'forty two'
+          expect{ clazz.new(*extra_values) }.to raise_error(ArgumentError)
+        end
       end
     end
   end