-94a:
- Inconsistencies between derived and declared VALUES return types for
- DEFUN aren't checked very well. E.g. the logic which successfully
- catches problems like
- (declaim (ftype (function (fixnum) float) foo))
- (defun foo (x)
- (declare (type integer x))
- (values x)) ; wrong return type, detected, gives warning, good!
- fails to catch
- (declaim (ftype (function (t) (values t t)) bar))
- (defun bar (x)
- (values x)) ; wrong number of return values, no warning, bad!
- The cause of this is seems to be that (1) the internal function
- VALUES-TYPES-EQUAL-OR-INTERSECT used to make the check handles its
- arguments symmetrically, and (2) when the type checking code was
- written back when when SBCL's code was still CMU CL, the intent
- was that this case
- (declaim (ftype (function (t) t) bar))
- (defun bar (x)
- (values x x)) ; wrong number of return values; should give warning?
- not be warned for, because a two-valued return value is considered
- to be compatible with callers who expects a single value to be
- returned. That intent is probably not appropriate for modern ANSI
- Common Lisp, but fixing this might be complicated because of other
- divergences between auld-style and new-style handling of
- multiple-VALUES types. (Some issues related to this were discussed
- on cmucl-imp at some length sometime in 2000.)
-