t next&&do end&=
        ^~ unexpected 'do'; expected an expression after the operator
  ^~~~ unexpected void value expression
  ^~~~ unexpected void value expression
^~~~~~~~~~~~~~ unexpected write target
              ^~ unexpected operator after a call with arguments
              ^~ unexpected operator after a call with a block
''while=
  ^~~~~ expected a predicate expression for the `while` statement
       ^ unexpected '='; target cannot be written