SOURCE_FILE
  FN
    FN_KW "fn"
    WHITESPACE " "
    NAME
      IDENT "foo"
    PARAM_LIST
      L_PAREN "("
      PARAM
        IDENT_PAT
          NAME
            IDENT "x"
        COLON ":"
        WHITESPACE " "
        IMPL_TRAIT_TYPE
          IMPL_KW "impl"
          WHITESPACE " "
          TYPE_BOUND_LIST
            TYPE_BOUND
              PATH_TYPE
                PATH
                  PATH
                    PATH
                      PATH_SEGMENT
                        NAME_REF
                          IDENT "std"
                    COLON2 "::"
                    PATH_SEGMENT
                      NAME_REF
                        IDENT "future"
                  COLON2 "::"
                  PATH_SEGMENT
                    NAME_REF
                      IDENT "Future"
                    GENERIC_ARG_LIST
                      L_ANGLE "<"
                      ASSOC_TYPE_ARG
                        NAME_REF
                          IDENT "Output"
                        WHITESPACE " "
                        EQ "="
                        WHITESPACE " "
                        PATH_TYPE
                          PATH
                            PATH_SEGMENT
                              NAME_REF
                                IDENT "i32"
                      R_ANGLE ">"
      R_PAREN ")"
    WHITESPACE " "
    BLOCK_EXPR
      STMT_LIST
        L_CURLY "{"
        R_CURLY "}"
  WHITESPACE "\n\n"
  FN
    FN_KW "fn"
    WHITESPACE " "
    NAME
      IDENT "main"
    PARAM_LIST
      L_PAREN "("
      R_PAREN ")"
    WHITESPACE " "
    BLOCK_EXPR
      STMT_LIST
        L_CURLY "{"
        WHITESPACE "\n    "
        CALL_EXPR
          PATH_EXPR
            PATH
              PATH_SEGMENT
                NAME_REF
                  IDENT "foo"
          ARG_LIST
            L_PAREN "("
            BLOCK_EXPR
              ASYNC_KW "async"
              WHITESPACE " "
              MOVE_KW "move"
              WHITESPACE " "
              STMT_LIST
                L_CURLY "{"
                WHITESPACE " "
                LITERAL
                  INT_NUMBER "12"
                WHITESPACE " "
                R_CURLY "}"
            R_PAREN ")"
        WHITESPACE "\n"
        R_CURLY "}"
  WHITESPACE "\n"