0.7.9.1:

[sbcl.git] / src / code / target-type.lisp

diff --git a/src/code/target-type.lisp b/src/code/target-type.lisp
index 6bbc5dd..d024ace 100644 (file)
--- a/src/code/target-type.lisp
+++ b/src/code/target-type.lisp
@@ -81,7 +81,26 @@
          (let ((predicate-name (second hairy-spec)))
            (declare (type symbol predicate-name)) ; by ANSI spec of SATISFIES
            (if (fboundp predicate-name)
-               (values (not (null (funcall predicate-name obj))) t)
+               (let* (;; "Is OBJ of the SATISFIES type?" represented
+                      ;; as a generalized boolean.
+                      ;;
+                      ;; (Why IGNORE-ERRORS? This code is used to try to
+                      ;; check type relationships at compile time. 
+                      ;; Passing only-slightly-twisted types like
+                      ;; (AND INTEGER (SATISFIES ODDP)) into the
+                      ;; rather-significantly-twisted type dispatch
+                      ;; system can easily give rise to oddities like
+                      ;; calling predicates like ODDP on values they
+                      ;; don't like. (E.g. on OBJ=#\NEWLINE when the
+                      ;; above type is tested for TYPE= against
+                      ;; STANDARD-CHAR, represented as a
+                      ;; MEMBER-TYPE.) In such cases, NIL seems to be
+                      ;; an appropriate answer to "is OBJ of the
+                      ;; SATISFIES type?")
+                      (gbool (ignore-errors (funcall predicate-name obj)))
+                      ;; RAW coerced to a pure BOOLEAN value
+                      (bool (not (not gbool))))
+                 (values bool t))
                (values nil nil)))))))))
 \f
 ;;; Return the layout for an object. This is the basic operation for