BlockScope of "Slop::Commands#new" is influenced by arity number

lib/slop/commands.rb

@@ -40,7 +40,15 @@ def initialize(config = {}, &block)
       @triggered_command = nil
 
       if block_given?
-        block.arity == 1 ? yield(self) : instance_eval(&block)
+        case block.arity.abs
+        when 0
+          instance_exec(&block)
+        when 1
+          instance_exec(self, &block)
+        else
+          raise ArgumentError,
+            "wrong number of block arguments (#{block.arity} for #{0..1})"
+        end
       end
     end
 
@@ -194,4 +202,4 @@ def execute_global_opts(items, bang)
     end
 
   end
-end
+end

test/commands_test.rb

@@ -99,4 +99,18 @@ def setup
     assert_equal %w( file1 file2 ), @commands.arguments
   end
 
+  test "new with block scope" do
+    peep = nil
+    ret = Slop::Commands.new { peep = self }
+    assert_same ret, peep
+
+    peep = nil
+    ret = Slop::Commands.new { |a| peep = self }
+    assert_same ret, peep
+
+    assert_raises ArgumentError do
+      Slop::Commands.new { |a, b| }
+    end
+  end
+
 end