parse.y: serial comparisons

* parse.y (rel_expr): warn sequence of comparisons, which would be
  probably unintentional.  [EXPERIMENTAL]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60207 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 8 insertions, 0 deletions

diff --git a/test/ruby/test_parse.rb b/test/ruby/test_parse.rb
index 769500a261..b9fa57f2c7 100644
--- a/test/ruby/test_parse.rb
+++ b/test/ruby/test_parse.rb
@@ -1069,6 +1069,14 @@ x = __ENCODING__
     assert_equal(1.3, o.x)
   end
 
+  def test_serial_comparison
+    assert_warning(/comparison '<' after/) do
+      $VERBOSE = true
+      x = 1
+      eval("if false; 0 < x < 2; end")
+    end
+  end
+
 =begin
   def test_past_scope_variable
     assert_warning(/past scope/) {catch {|tag| eval("BEGIN{throw tag}; tap {a = 1}; a")}}