SOURCE_FILE
  FN
    FN_KW "fn"
    WHITESPACE " "
    NAME
      IDENT "f"
    PARAM_LIST
      L_PAREN "("
      R_PAREN ")"
    WHITESPACE " "
    RET_TYPE
      THIN_ARROW "->"
      WHITESPACE " "
      IMPL_TRAIT_TYPE
        IMPL_KW "impl"
        WHITESPACE " "
        TYPE_BOUND_LIST
          TYPE_BOUND
            PATH_TYPE
              PATH
                PATH_SEGMENT
                  NAME_REF
                    IDENT "Iterator"
                  GENERIC_ARG_LIST
                    L_ANGLE "<"
                    ASSOC_TYPE_ARG
                      NAME_REF
                        IDENT "Item"
                      WHITESPACE " "
                      EQ "="
                    WHITESPACE " "
                    COMMA ","
                    WHITESPACE " "
                    ASSOC_TYPE_ARG
                      NAME_REF
                        IDENT "Item"
                      WHITESPACE " "
                      EQ "="
                    WHITESPACE " "
                    R_ANGLE ">"
    WHITESPACE " "
    BLOCK_EXPR
      STMT_LIST
        L_CURLY "{"
        R_CURLY "}"
  WHITESPACE "\n"
error 30: missing associated item binding
error 39: missing associated item binding
