In Ruby 2.0, you can have a space between -> and () in lambdas (this was not allowed in 1.9 and earlier). This patch modifies the lexer to allow this in --2.0 mode.
I've added specs to RubySpec to test this in rubyspec/rubyspec#251
Allow whitespace between -> and () in lambdas in 2.0
See c0aacb4 and 5f4aa16