Raise TypeError without String argument same as C version

Author: hsbt

lib/pathname.rb

@@ -239,6 +239,9 @@ class Pathname
   #
   def initialize(path)
     path = path.to_path if path.respond_to? :to_path
+
+    raise TypeError unless path.is_a?(String) # Compatibility for C version
+
     if path.include?("\0")
       raise ArgumentError, "pathname contains \\0: #{path.inspect}"
     end