+ (let ((use (principal-lvar-use lvar))
+ (type (lvar-type lvar))
+ leaf)
+ (cond ((and (ref-p use)
+ (constant-p (setf leaf (ref-leaf use))))
+ (constant-value leaf))
+ ((and (member-type-p type)
+ (eql 1 (member-type-size type)))
+ (first (member-type-members type)))
+ (t
+ (error "~S used on non-constant LVAR ~S" 'lvar-value lvar)))))