syntax_diff_search.rb

all_tokens = %w[
  x
  y
  false
  if
  rescue
  begin
  end
  =
  def
  =>
  *
  for
  in
  ,
  (
  )
]
loop {
  code = 7.times.map { all_tokens.sample }.join(' ')
  next unless Prism.parse_success?(code) && Ripper.sexp(code)
  $><<'|'# if rand < 0.001
  $VERBOSE=nil
  def x; $a<<:x; end; def y; $a<<:y; end
  $a=[];$a<<begin;RubyVM::InstructionSequence.compile_parsey(code).eval; rescue;:err;end;
  parsey=$a
  def x; $a<<:x; end; def y; $a<<:y; end
  $a=[];$a<<begin;RubyVM::InstructionSequence.compile_prism(code).eval; rescue;:err;end;
  prism=$a
  p code if parsey!=prism && !(parsey+prism).include?(:syntax)
}

___END__
# found differences
7
y = x rescue x in *
8
def false = y rescue y in x
x = begin end rescue x in false
9
x = x rescue x = x => *
x = y rescue false in * , y