anchor.diff:     | block
      ;
   
  -const
  +const_
      : '-'? number
      | 'none'
      | 'univ'
  
positive.code:    ;
  
  import_
     : 'open' qualName (qualName (',' qualName)*)? ('as' name)?
     ;
  
  paragraph
  
negative.code: assertDecl
     : 'assert' name? block
     ;
     // qualname | bloclk should be optional
     
  cmdDecl
     : (name ':')? ('run' | 'check')? (qualName | block) scope?
     ;
  
  scope
  