anchor.diff:      ((interpolatedExpressionStart) => expression SIMPLESTRINGLITERAL)+
       ;
   
  -//special rule for syntactic predicates
  +//special rule for syntactic predicate
  +//to distinguish an interpolated expression
  +//in a string template
   //this includes every token that could be 
   //the beginning of an expression, except 
   //for SIMPLESTRINGLITERAL and '['
  
positive.code:     )
      ;
  
  //special rule for syntactic predicates
  annotatedDeclarationStart
      : declarationStart
      | LIDENTIFIER
  
negative.code:       )
      ;
  
  //special rule for syntactic predicates
  //that distinguish declarations from
  //expressions
  declarationStart
      : declarationKeyword 
      | type '...'? LIDENTIFIER
  