anchor.diff:      body  = '$5'
     }.
   
  -function_body -> '$empty'  : [#nil{}].
  -function_body -> expr_list : '$1'.
  +body -> '$empty'  : [#nil{}].
  +body -> expr_list : '$1'.
   
   %% Class instantiations
   class_inst -> module_name pargs :
  
positive.code: clauses -> clause clauses : ['$1'|'$2'].
  clauses -> clause : ['$1'].
  
  clause -> when inline_exprs eol expr_list : 
    #clause{
      line=?line('$1'), 
      patterns='$2', 
  
negative.code:   class_decl
    functions
    function
    body
    pargs
    pargs_tail
    block_capture
  