list callers dies on :method

[Steven C. Bagley <bagley at MIT-OZ>]

In Symbolics 3600 Release 5.2, FEP 18, on Lisp Machine Robot-1:

I did M-X list callers, then clicked on the box around
(interp-generator :next-interp) in the following line:
(defmethod (interp-generator :next-interp) ()
...
and it blew out thusly:

>>Error: The argument SYMBOLS to SI:FIND-CALLERS-OF-SYMBOLS, ((:METHOD INTERP-GENERATOR :NEXT-INTERP)), was of the wrong type.
         The function expected a symbol or a list of symbols.
While in the function SI:FIND-CALLERS-OF-SYMBOLS  (:METHOD ZWEI:CALLERS-OF-FUNCTIONS-EDITING-BUFFER :REVERT)  (:METHOD ZWEI:CALLERS-OF-FUNCTIONS-EDITING-BUFFER :COMBINED :REVERT)

SI:FIND-CALLERS-OF-SYMBOLS:  (P.C. = 103)
   Arg 0 (SYMBOLS-initialization): ((:METHOD INTERP-GENERATOR :NEXT-INTERP))
   Arg 1 (PKG): #<Package SHAPE 5145601>
   Arg 2 (FUNCTION-initialization): #<DTP-COMPILED-FUNCTION (:INTERNAL (:METHOD ZWEI:CALLERS-OF-FUNCTIONS-EDITING-BUFFER :REVERT) 0.) 44644315>
   --Defaulted args:--
   Arg 3 (DO-INFERIORS): T
   Arg 4 (DO-SUPERIORS): T

(:METHOD ZWEI:CALLERS-OF-FUNCTIONS-EDITING-BUFFER :REVERT):  (P.C. = 15)
   Arg 0 (SELF): #<CALLERS-OF-FUNCTIONS-EDITING-BUFFER "*Callers-2*" 53276307>
   Arg 1 (SELF-MAPPING-TABLE): #<Map to flavor ZWEI:CALLERS-OF-FUNCTIONS-EDITING-BUFFER -- 3. IV's, 4. FL's 45650374>
   Arg 2 (OPERATION): :REVERT

(:METHOD ZWEI:CALLERS-OF-FUNCTIONS-EDITING-BUFFER :COMBINED :REVERT):  (P.C. = 15)
   Arg 0 (SELF): #<CALLERS-OF-FUNCTIONS-EDITING-BUFFER "*Callers-2*" 53276307>
   Arg 1 (SELF-MAPPING-TABLE): #<Map to flavor ZWEI:CALLERS-OF-FUNCTIONS-EDITING-BUFFER -- 3. IV's, 4. FL's 45650374>
   Rest arg (.DAEMON-CALLER-ARGS.): NIL

(:METHOD ZWEI:ZMACS-EDITOR :FIND-SPECIAL-BUFFER):  (P.C. = 45)
   Arg 0 (SELF): #<ZMACS-TOP-LEVEL-EDITOR 35672207>
   Arg 1 (SELF-MAPPING-TABLE): #<Map to flavor ZWEI:ZMACS-EDITOR -- 3. IV's, 0. FL's 42623345>
   Arg 2 (OPERATION): :FIND-SPECIAL-BUFFER
   Arg 3 (TYPE): :CALLERS-OF-FUNCTIONS
   Arg 4 (NEW-P): T
   Rest arg (SETS): (:SET-FUNCTION-SPECS ((:METHOD INTERP-GENERATOR :NEXT-INTERP)) :SET-PACKAGE-TO-SEARCH #<Package SHAPE 5145601> :SET-NAME-OF-PACKAGE-TO-SEARCH "package SHAPE")

(:DEFUN-METHOD ZWEI:PUSH-POSSIBILITIES-BUFFER):  (P.C. = 10)
   Arg 0 (SELF): #<ZMACS-TOP-LEVEL-EDITOR 35672207>
   Arg 1 (SELF-MAPPING-TABLE): #<Map to flavor ZWEI:ZMACS-EDITOR -- 3. IV's, 0. FL's 42623345>
   Arg 2 (ACTION): :LIST-POSSIBILITIES
   Arg 3 (TYPE): :CALLERS-OF-FUNCTIONS
   Rest arg (SET-OPTIONS): (:SET-FUNCTION-SPECS ((:METHOD INTERP-GENERATOR :NEXT-INTERP)) :SET-PACKAGE-TO-SEARCH #<Package SHAPE 5145601> :SET-NAME-OF-PACKAGE-TO-SEARCH "package SHAPE")

ZWEI:PUSH-POSSIBILITIES-BUFFER:  (P.C. = 12)
   Rest arg (ARGS): (:LIST-POSSIBILITIES :CALLERS-OF-FUNCTIONS :SET-FUNCTION-SPECS ((:METHOD INTERP-GENERATOR :NEXT-INTERP)) :SET-PACKAGE-TO-SEARCH #<Package SHAPE 5145601> :SET-NAME-OF-PACKAGE-TO-SEARCH "package SHAPE")

ZWEI:WHO-CALLS-INTERNAL:  (P.C. = 62)
   Arg 0 (PROMPT): "List"
   Arg 1 (ACTION): :LIST-POSSIBILITIES
   --Defaulted args:--
   Arg 2 (MUST-BE-DEFINED-FLAG): NIL

ZWEI:COM-LIST-CALLERS:  (P.C. = 4)

Rest of stack:
ZWEI:COM-EXTENDED-COMMAND:  (P.C. = 27)
ZWEI:COMMAND-EXECUTE:  (P.C. = 55)
ZWEI:PROCESS-COMMAND-CHAR:  (P.C. = 14)
(:METHOD ZWEI:EDITOR :EDIT):  (P.C. = 214)
(:METHOD ZWEI:TOP-LEVEL-EDITOR :COMBINED :EDIT):  (P.C. = 41)
ZWEI:ZMACS-WINDOW-TOP-LEVEL:  (P.C. = 16)
SI:PROCESS-TOP-LEVEL:  (P.C. = 53)