SBCL注意:类型断言太复杂，无法检查

Question

在破译SBCL编译器消息时遇到困难：

; in: DEFUN PURIFY-FILE
;     (DEFUN DEPENDENCIES::PURIFY-FILE (DEPENDENCIES::FILE)
;       "Transforms problematic symbols to benign NIL in file, before reading.
;      Returns a string of altered file content."
;       (LET ((DEPENDENCIES::FILE-STRING
;              (ALEXANDRIA:READ-FILE-INTO-STRING DEPENDENCIES::FILE))
;             (DEPENDENCIES::MODIFIED-FILE-STRING ""))
;         (SETF DEPENDENCIES::MODIFIED-FILE-STRING
;                 (CL-PPCRE:REGEX-REPLACE-ALL "[ trn]'[A-Za-z0-9!@$%&*_+:=<.>/?-]+"
;                                             DEPENDENCIES::FILE-STRING " NIL"))
;         (CL-PPCRE:REGEX-REPLACE-ALL
;          "[(][qQ][uU][oO][tT][eE][ trn]+[A-Za-z0-9!@$%&*_+:=<.>/?-]+[)]"
;          DEPENDENCIES::MODIFIED-FILE-STRING "NIL")))
; --> PROGN SB-IMPL::%DEFUN SB-IMPL::%DEFUN SB-INT:NAMED-LAMBDA
; ==>
;   #'(SB-INT:NAMED-LAMBDA DEPENDENCIES::PURIFY-FILE
;         (DEPENDENCIES::FILE)
;       (DECLARE (SB-C::TOP-LEVEL-FORM))
;       "Transforms problematic symbols to benign NIL in file, before reading.
;    Returns a string of altered file content."
;       (BLOCK DEPENDENCIES::PURIFY-FILE
;         (LET ((DEPENDENCIES::FILE-STRING #)
;               (DEPENDENCIES::MODIFIED-FILE-STRING ""))
;           (SETF DEPENDENCIES::MODIFIED-FILE-STRING #)
;           (CL-PPCRE:REGEX-REPLACE-ALL
;            "[(][qQ][uU][oO][tT][eE][ trn]+[A-Za-z0-9!@$%&*_+:=<.>/?-]+[)]"
;            DEPENDENCIES::MODIFIED-FILE-STRING "NIL"))))
;
; note: type assertion too complex to check:
; (VALUES STRING &OPTIONAL BOOLEAN &REST T).

我对此函数的规范是(declaim (ftype (function (pathname) (values string (member NIL T))) purify-file))

是不是因为CL-PPCRE:REGEX-REPLACE-ALL返回了多个值？如果是这样，如何使用ftype指定所有多个值的类型--在本例中是字符串& NIL或T？谢谢。

Answer 1

事实上，正如消息所表明的那样，类型for (values string (member NIL T))对于SBCL来说太复杂了。将类型the更改为(values t t) works。