SOURCE_FILE
  FN
    FN_KW "fn"
    WHITESPACE " "
    NAME
      IDENT "main"
    PARAM_LIST
      L_PAREN "("
      R_PAREN ")"
    WHITESPACE " "
    BLOCK_EXPR
      STMT_LIST
        L_CURLY "{"
        WHITESPACE " "
        LET_STMT
          LET_KW "let"
          WHITESPACE " "
          PATH_PAT
            PATH
              PATH
                PATH_SEGMENT
                  L_ANGLE "<"
                  INFER_TYPE
                    UNDERSCORE "_"
                  R_ANGLE ">"
              COLON2 "::"
              PATH_SEGMENT
                NAME_REF
                  IDENT "Foo"
          WHITESPACE " "
          EQ "="
          WHITESPACE " "
          TUPLE_EXPR
            L_PAREN "("
            R_PAREN ")"
          SEMICOLON ";"
        WHITESPACE " "
        R_CURLY "}"
  WHITESPACE "\n"