anchor.diff:  map_fields -> map_field : ['$1'].
   map_fields -> map_field ',' map_fields : ['$1' | '$3'].
   
  -map_field -> map_key '=>' expr :
  -	{map_field,?line('$1'),'$1','$3'}.
  +map_field -> map_field_assoc : '$1'.
  +map_field -> map_field_exact : '$1'.
  +
  +map_field_assoc -> map_key '=>' expr :
  +	{map_field_assoc,?line('$1'),'$1','$3'}.
  +
  +map_field_exact -> map_key ':=' expr :
  +	{map_field_exact,?line('$1'),'$1','$3'}.
   
   map_key -> expr : '$1'.
   
  
positive.code: '*' '/' 'div' 'rem' 'band' 'and'
  '+' '-' 'bor' 'bxor' 'bsl' 'bsr' 'or' 'xor'
  '++' '--'
  '==' '/=' '=<' '<' '>=' '>' '=:=' '=/=' '<=' '=>'
  '<<' '>>'
  '!' '=' '::' '..' '...'
  'spec' 'callback' % helper
  
negative.code: tuple
  %struct
  record_expr record_tuple record_field record_fields
  map_expr map_tuple map_field map_field_assoc map_field_exact map_fields map_key
  if_expr if_clause if_clauses case_expr cr_clause cr_clauses receive_expr
  fun_expr fun_clause fun_clauses atom_or_var integer_or_var
  try_expr try_catch try_clause try_clauses
  