ruby_prism_compare.rb

def run
  $VERBOSE=nil
  tokens = %w[1 + * ** a in ( ) [ ] = . .. => <<]
  cnt = 0
  output = {}
  (2..8).each do |n|
    cnt = 0
    tokens.repeated_permutation(n).each do |tokens|
      code = tokens.join('') # or join(' ')
      # Ruby's bug already fixed in 3.3
      next if code.end_with?('1.')
      next if code.include?('..=') # a..==1
      next if code.include?('..<<') # a..<<+1
      a = begin;RubyVM::AbstractSyntaxTree.parse(code);true;rescue SyntaxError;false;end
      b = Prism.parse_success?(code)
      unless a == b
        cnt += 1
        v = Suppresser.new
        v.visit(Prism.parse(code).value) if b
        if v.matched
          (output[v.matched] ||= []) << code
        else
          p [code, a, b]
        end
      end
    end
    p [n, cnt]
    p output.transform_values(&:size).sort_by(&:last)
  end
  binding.irb
end

class Suppresser < Prism::Visitor
  attr_reader :matched

  def visit_call_node(node)
    super
    # + b = *c
    @matched = __LINE__ if node in { opening_loc: nil, receiver: { depth:, value: Prism::SplatNode } }
    # a b = *c
    @matched = __LINE__ if node in { arguments: { arguments: [{ depth:, value: Prism::SplatNode }] } }
    # a( a = * 1 )
    @matched = __LINE__ if node in { arguments: { arguments: [{ depth:, value: Prism::SplatNode }] } }
    # a 1 .. * 1
    @matched = __LINE__ if node in { receiver: { receiver:, opening_loc: nil } }
    # + ( * ) = 1
    @matched = __LINE__ if node in { receiver: Prism::MultiWriteNode }
    # a = b .. * c
    @matched = __LINE__ if node in { receiver: Prism::LocalVariableWriteNode }
    # ( + ( * ) )
    @matched = __LINE__ if node in { receiver: Prism::MultiTargetNode }
    # + 1 [ ] = * 1
    @matched = __LINE__ if node in { opening_loc: nil, receiver: { name: /=\z/, arguments: { arguments: [Prism::SplatNode]} } }
    # a a . a = * a
    @matched = __LINE__ if node in { opening_loc: nil, arguments: { arguments: [{ name: /=\z/, arguments: { arguments: [Prism::SplatNode] } }] } }
  end

  def visit_call_operator_write_node(node)
    super
    # a.* += 1
    @matched = __LINE__ if node in { write_name: /[-+*\/%&|<=>^]=\z/ }
    # a.[] += 1
    @matched = __LINE__ if node in { write_name: :[]=, call_operator_loc: Prism::Location }
  end

  def visit_arguments_node(node)
    super
    # ( a ( * ) )
    # (a.b = ( * ))
    @matched = __LINE__ if node in { arguments: [*, Prism::MultiTargetNode, *] }
    # a ( * ) = b
    # a[ ( * ) = 1 ]
    @matched = __LINE__ if node in { arguments: [*, Prism::MultiWriteNode, *] }
    # a[ * a = * 1 ]
    @matched = __LINE__ if node in { arguments: [*, { expression: Prism::LocalVariableWriteNode }, *] }
  end

  def visit_hash_pattern_node(node)
    super
    # a in (**)
    # a in [**]
    @matched = __LINE__ if node in { opening_loc: nil }
  end

  def visit_array_node(node)
    super
    # [ a = * b ]
    @matched = __LINE__ if node in { elements: [*, { depth:, value: Prism::SplatNode }, *] }
    # [ ( * ) = a ]
    @matched = __LINE__ if node in { elements: [*, Prism::MultiWriteNode, *] }
    # [ * a = * b ]
    # a = * a = * b
    @matched = __LINE__ if node in { elements: [*, { expression: Prism::LocalVariableWriteNode }, *] }
  end

  def visit_assoc_splat_node(node)
    super
    # a(** a = * a)
    @matched = __LINE__ if node in { value: { depth:, value: Prism::SplatNode } }
  end
  
  def visit_assoc_node(node)
    super
    # a a = * 1 => 1
    @matched = __LINE__ if node in { key: { depth:, value: Prism::SplatNode } }
    # a 1 => b = * c
    @matched = __LINE__ if node in { value: { depth:, value: Prism::SplatNode } }
    # a a 1 => 1 => 1
    @matched = __LINE__ if node in { key: { receiver:, opening_loc: nil, arguments: [Prism::Node, *]} }
  end

  def visit_splat_node(node)
    super
    # * = * a = * 1
    @matched = __LINE__ if node in { expression: { depth:, value: Prism::SplatNode } }
  end

  def visit_splat_node(node)
    super
    # a(* a = * a)
    @matched = __LINE__ if node in { expression: { depth:, value: Prism::SplatNode } }
  end

  def visit_range_node(node)
    super
    # a .. b..
    @matched = __LINE__ if node in { right: Prism::RangeNode }
    # + .. a ..
    # a + .. b ..
    @matched = __LINE__ if node in { left: { receiver:, call_operator_loc: nil } }
    # * = .. 1 ..
    @matched = __LINE__ if node in { left: Prism::MultiWriteNode }
    # a = .. 1 ..
    @matched = __LINE__ if node in { left: Prism::LocalVariableWriteNode }
    # a . b = .. 1 ..
    @matched = __LINE__ if node in { left: { receiver:, name: /=\z/ } }
    # a+=..1..
    @matched = __LINE__ if node in { left: Prism::LocalVariableOperatorWriteNode }
    # .. a = *b
    @matched = __LINE__ if node in { right: { depth:, value: Prism::SplatNode } }
    # ( .. ( * ) )
    @matched = __LINE__ if node in { right: Prism::MultiTargetNode }
    # .. ( * ) = 1
    @matched = __LINE__ if node in { right: Prism::MultiWriteNode }
    # .. 1 [ ] = * 1
    @matched = __LINE__ if node in { right: { name: /=\z/, arguments: { arguments: [Prism::SplatNode] } } }
  end

  def visit_match_predicate_node(node)
    super
    # a, b = c in d
    @matched = __LINE__ if node in { value: Prism::MultiWriteNode }
    # a b in c
    @matched = __LINE__ if node in { value: { receiver:, opening_loc: nil, arguments: [Prism::Node,] } }
    # a = * 1 in 1
    @matched = __LINE__ if node in { value: { depth:, value: { elements: [*, Prism::SplatNode, *] } } }
    # a = b 1 in 1
    @matched = __LINE__ if node in { value: { depth:, value: { receiver:, opening_loc: nil } } }
  end

  def visit_match_required_node(node)
    super
    # * = 1 => 1
    @matched = __LINE__ if node in { value: Prism::MultiWriteNode }
    # a 1 => 1 => 1
    @matched = __LINE__ if node in { value: { receiver:, opening_loc: nil } }
    # a = * 1 => 1
    @matched = __LINE__ if node in { value: { depth:, value: { elements: [*, Prism::SplatNode, *] } } }
  end

  def visit_capture_pattern_node(node)
    super
    # 1 in a => a
    @matched = __LINE__ if node in { value: { name: }, target: { name: ^name } }
    # 1 in 1 => a => a
    @matched = __LINE__ if node in { value: { target: { name: } }, target: { name: ^name } }
    # 1 in a => b => a
    @matched = __LINE__ if node in { value: { value: { name: } }, target: { name: ^name } }
    # 1 in [a] => a
    @matched = __LINE__ if node in { value: { requireds: [{ name: }] }, target: { name: ^name } }
    # 1 in [a] => b => a
    @matched = __LINE__ if node in { value: { value: { requireds: [{ name: }] } }, target: { name: ^name } }
  end

  def visit_splat_node(node)
    super
    # * ( * ) = 1
    @matched = __LINE__ if node in { expression: Prism::MultiTargetNode}
  end

  def visit_local_variable_write_node(node)
    super
    # a = a = *a
    @matched = __LINE__ if node in { value: { name:, value: Prism::SplatNode } }
    # a = ( * ) = 1
    @matched = __LINE__ if node in { value: Prism::MultiWriteNode }
    # ( a = ( * ) )
    @matched = __LINE__ if node in { value: Prism::MultiTargetNode }
    # a = * a = * 1
    @matched = __LINE__ if node in { value: { elements: []} }
  end

  def visit_multi_write_node(node)
    super
    # * = a = *a
    @matched = __LINE__ if node in { value: { depth:, value: Prism::SplatNode } }
    # * = ( * ) = 1
    @matched = __LINE__ if node in { value: Prism::MultiWriteNode }
    # ( * = ( * ) )
    @matched = __LINE__ if node in { value: Prism::MultiTargetNode }
  end
end

run