1.9 compat

Do not use colons to separate if/unless/when conditions from expressions:

  # e.g. adva_cms, ansuz, cruisecontrol, freemium, merb, paperclip, radiant, 
  # rbot, rfpdf, rghost, rstomp, shoulda, typus
  case true; when TrueClass: true; end

  # ruby 1.8.7
  => true
  # ruby 1.9.1
  => syntax error, unexpected ':', expecting keyword_then or ',' or ';' or '\n'


Do not use instance_variables, constants or hash access as block parameters:

  # e.g. in cruise_control, spree
  lambda { |@foo| }

  # ruby 1.8.7
  => #<Proc:0x00000000@(irb):1>
  # ruby 1.9.1
  formal argument cannot be an instance variable
  
  # e.g. in cruisecontrol (frozen rails)
  lambda { |foo[:bar]| }
  
  # ruby 1.8.7
  => #<Proc:0x00000000@(irb):1>
  # ruby 1.9.1
  formal argument cannot be a constant

  # e.g. in cruisecontrol (frozen rails)
  lambda { |foo[:bar]| }
  
  # ruby 1.8.7
  => #<Proc:0x00000000@(irb):1>
  # ruby 1.9.1
  => syntax error, unexpected '[', expecting '|'
  
  
Do not use dangling commas in parameter lists:

  # e.g. in cruisecontrol (frozen rails)
  lambda { |(foo, )| }

  # ruby 1.8.7
  => #<Proc:0x00000000@(irb):1>
  # ruby 1.9.1
  => syntax error, unexpected ')'


Do not use commas to separate key and value in a Hash:

  # e.g. cosy, streamlined, webrat
  {1, 2}

  # ruby 1.8.7
  => {1 => 2}
  # ruby 1.9.1
  => syntax error, unexpected ',', expecting tASSOC
  
  
Do not put spaces in front of parentheses (method call arguments):
  
  # e.g. in exception_logger (logged_exceptions_controller.rb:40, logged_exceptions_helper.rb:9)
  A.foo (:bar)
  
  # ruby 1.9.1
  => syntax error, unexpected ',', expecting ')'
  
  
Do not put spaces in front of brackets (Hash access):

  # e.g. in ultrasphinx (configure.rb:247)
  entry ['association_name']  
  
  # ruby 1.9.1
  => syntax error, unexpected tLBRACK, expecting keyword_do or '{' or '('
  
  
Put a space between the operator and number when calculating:

  # e.g. in liquid (htmltags.rb:49, for.rb:104, paginate.rb:61)
  a - b -1
  
  # ruby 1.9.1
  => syntax error, unexpected tUMINUS_NUM, expecting keyword_do or '{' or '('
  
  # e.g. in prawn (span.rb:36)
  a /2.0
  
  # ruby 1.9.1
  => syntax error, unexpected tREGEXP_BEG, expecting keyword_do or '{' or '('
  
Don't use a star/splat operator on the righthand side of an options (bare) hash
when calling a method.
  
  # e.g. in typo (active_record.rb:5)
  def foo(*args) ; end
  foo(:baz => :buz, *options)

  # ruby 1.8.7
  nil
  # ruby 1.9.1
  => syntax error, unexpected tSTAR, expecting ')'