Improved test coverage for Array#flatten.

These tests pass for me on 1.8.7 (2010-08-16 patchlevel 302) and 1.9.2p14 (2010-10-02 revision 29393).

core/array/flatten_spec.rb

@@ -92,6 +92,30 @@
    ary.flatten
    ary.should == [1, [2, 3]]
  end

  it "ignores NoMethodError raised by calling to_ary on element with no to_ary method" do
    obj = Object.new
    lambda { [obj].flatten.should == [obj] }.should_not raise_error(NoMethodError)
  end

  it "ignores the return value of to_ary if it is nil" do
    obj = Class.new do
      def to_ary
        nil
      end
    end.new
    [obj].flatten.should == [obj]
  end

  it "raises TypeError if return value of to_ary is not an Array" do
    obj = Class.new do
      def to_ary
        1
      end
    end.new
    lambda { [obj].flatten }.should raise_error(TypeError)
  end

end

describe "Array#flatten!" do