Trivial Incompatibility


a Lot of Enhancement
    * New syntax and semantics
          o Method used for splat arguments: #to_splat
          o defined? and local variables
    * Kernel and Object
          o Kernel#require
    * Class and Module
          o Class variables behavior
          o Module#attr is an alias of attr_reader
          o Module#instance_methods, #private_instance_methods, #public_instance_methods
          o Extra subclassing check when binding UnboundMethods
    * Exceptions
          o Equality of exceptions
          o SystemStackError
          o SecurityError
          o Removed Exception#to_str
    * Array
          o Array#nitems
          o Array#[m,n] = nil places nil in the array.
    * Hash
          o New literal hash syntax
          o Hash#to_s is equivalent to Hash#inspect
          o Semantics for Hash#each and Hash#each_pair
          o Hash#select
    * Integer
          o Integer(nil) raises TypeError
    * Struct
          o Struct#inspect
    * File and Dir operations
          o #to_path in File.path, File.chmod, File.lchmod, File.chown, File.lchown, File.utime, File.unlink...
          o Dir.[], Dir.glob
          o Dir.exist?
    * IO operations
          o Non-blocking IO
          o IO#getbyte, IO#readbyte, StringIO#getbyte, StringIO#readbyte
          o Kernel#open [Ruby2]
          o IO#initialize now accepts an IO argument
          o StringIO#readpartial
          o IO#lines
          o IO#bytes
          o IO.try_convert
          o Limit input in IO#gets, IO#readline, IO#readlines, IO#each_line, IO#lines, IO.foreach, IO.readlines, StringIO#gets, StringIO#readline, StringIO#each, StringIO#readlines
          o IO#ungetc, StringIO#ungetc
    * Time
          o New format in Time#to_s
          o Timezone information preserved on Marshal.dump/load
    * Symbols: restriction on literal symbols
    * $SAFE and bound methods