SOURCE_FILE
  FN
    FN_KW "fn"
    WHITESPACE " "
    NAME
      IDENT "foo"
    PARAM_LIST
      L_PAREN "("
      R_PAREN ")"
    WHITESPACE " "
    BLOCK_EXPR
      STMT_LIST
        L_CURLY "{"
        WHITESPACE "\n    "
        LET_STMT
          LET_KW "let"
          WHITESPACE " "
          WILDCARD_PAT
            UNDERSCORE "_"
          WHITESPACE " "
          EQ "="
          WHITESPACE " "
          PATH_EXPR
            PATH
              PATH_SEGMENT
                NAME_REF
                  IDENT "a"
          SEMICOLON ";"
        WHITESPACE "\n    "
        LET_STMT
          LET_KW "let"
          WHITESPACE " "
          WILDCARD_PAT
            UNDERSCORE "_"
          WHITESPACE " "
          EQ "="
          WHITESPACE " "
          PATH_EXPR
            PATH
              PATH
                PATH_SEGMENT
                  NAME_REF
                    IDENT "a"
              COLON2 "::"
              PATH_SEGMENT
                NAME_REF
                  IDENT "b"
          SEMICOLON ";"
        WHITESPACE "\n    "
        LET_STMT
          LET_KW "let"
          WHITESPACE " "
          WILDCARD_PAT
            UNDERSCORE "_"
          WHITESPACE " "
          EQ "="
          WHITESPACE " "
          PATH_EXPR
            PATH
              PATH_SEGMENT
                COLON2 "::"
                NAME_REF
                  IDENT "a"
                GENERIC_ARG_LIST
                  COLON2 "::"
                  L_ANGLE "<"
                  TYPE_ARG
                    PATH_TYPE
                      PATH
                        PATH_SEGMENT
                          NAME_REF
                            IDENT "b"
                  R_ANGLE ">"
          SEMICOLON ";"
        WHITESPACE "\n    "
        LET_STMT
          LET_KW "let"
          WHITESPACE " "
          WILDCARD_PAT
            UNDERSCORE "_"
          WHITESPACE " "
          EQ "="
          WHITESPACE " "
          MACRO_EXPR
            MACRO_CALL
              PATH
                PATH_SEGMENT
                  NAME_REF
                    IDENT "format"
              BANG "!"
              TOKEN_TREE
                L_PAREN "("
                R_PAREN ")"
          SEMICOLON ";"
        WHITESPACE "\n"
        R_CURLY "}"
  WHITESPACE "\n"
