anchor.diff:  letins:
      'let' letbind (',' letbind)* 'in' expr;
   
  +arrayLiteral : LBRACKET exprs? RBRACKET ;
  +
   expr:
  -     ifExpr
  +     arrayLiteral
  +   | ifExpr
      | letins
      | infixExpr
      ;
  
positive.code: 
  grammar Lasca;
  
  valDef: VAL Id (':' type)? '=' expr;
  
  literal:
        IntegerLiteral # integer
  
negative.code:    ;
  
  prefixExpr
     : UnaryOp? (closureExpr | blockExpr | simpleExpr1)
     ;
  
  simpleExpr1:
  