mruby-range-ext: update overlap? to handle empty ranges

The code is taken from ActiveSupport (Rails).

mrbgems/mruby-range-ext/mrblib/range.rb

@@ -102,6 +102,30 @@ class Range
   #  (1..5).overlap?(7..9) # => false
   def overlap?(other)
     raise TypeError, "argument must be a range" unless other.kind_of?(Range)
-    other.begin == self.begin || self.cover?(other.begin) || other.cover?(self.begin)
+
+    self_begin = self.begin
+    other_end = other.end
+    other_excl = other.exclude_end?
+
+    return false if __empty_range?(self_begin, other_end, other_excl)
+
+    other_begin = other.begin
+    self_end = self.end
+    self_excl = self.exclude_end?
+
+    return false if __empty_range?(other_begin, self_end, self_excl)
+    return true if self_begin == other_begin
+
+    return false if __empty_range?(self_begin, self_end, self_excl)
+    return false if __empty_range?(other_begin, other_end, other_excl)
+
+    true
+  end
+
+  def __empty_range?(b, e, excl)
+    return false if b.nil? || e.nil?
+
+    comp = b <=> e
+    comp.nil? || comp > 0 || (comp == 0 && excl)
   end
 end