--- a/Method.st	Thu Mar 09 10:45:46 1995 +0100
+++ b/Method.st	Thu Mar 09 11:44:00 1995 +0100
@@ -12,7 +12,9 @@
 
 CompiledCode subclass:#Method
        instanceVariableNames:'source sourcePosition category package'
-       classVariableNames:'PrivateMethodSignal LastFileReference LastSourceFileName'
+       classVariableNames:'PrivateMethodSignal 
+			   LastFileReference LastSourceFileName
+			   LastWhoClass'
        poolDictionaries:''
        category:'Kernel-Methods'
 !
@@ -21,7 +23,7 @@
 COPYRIGHT (c) 1989 by Claus Gittinger
 	     All Rights Reserved
 
-$Header: /cvs/stx/stx/libbasic/Method.st,v 1.29 1995-03-08 23:38:42 claus Exp $
+$Header: /cvs/stx/stx/libbasic/Method.st,v 1.30 1995-03-09 10:44:00 claus Exp $
 '!
 
 !Method class methodsFor:'documentation'!
@@ -42,7 +44,7 @@
 
 version
 "
-$Header: /cvs/stx/stx/libbasic/Method.st,v 1.29 1995-03-08 23:38:42 claus Exp $
+$Header: /cvs/stx/stx/libbasic/Method.st,v 1.30 1995-03-09 10:44:00 claus Exp $
 "
 !
 
@@ -571,17 +573,46 @@
      - the information about which class the original method was 
      defined in is lost in this case.
 
-     Q: should we add a backref from the method to the class ?"
+     Problem: this is heavily called for in the debugger to create
+	      a readable context walkback. For unbound methods, it is
+	      slow, since the search (over all classes) will always fail.
+     Q: should we add a backref from the method to the class 
+	and/or add a subclass of Method for unbound ones ?"
+
+    |classes cls sel|
+
+    "
+     very first, look in the class we found something the last time
+     this may often give a hit, when asking who repeatingly for
+     a context chain. (keep last by its name, to not keep classes from
+     being garbage collected)
+    "
+    LastWhoClass notNil ifTrue:[
+	cls := Smalltalk at:LastWhoClass.
+	sel := cls selectorForMethod:self.
+	sel notNil ifTrue:[^ Array with:cls with:sel].
+    ].
 
     "
      first, limit the search to global classes only - 
      since probability is high, that the receiver is found in there ...
     "
-    Smalltalk allBehaviorsDo:[:aClass |
+    classes := Smalltalk allBehaviors.
+    "
+     instance methods are usually more common - search those first
+    "
+    classes do:[:aClass |
 	|sel|
 
 	sel := aClass selectorForMethod:self.
-	sel notNil ifTrue:[^ Array with:aClass with:sel].
+	sel notNil ifTrue:[LastWhoClass := aClass name.
+			   ^ Array with:aClass with:sel].
+    ].
+
+    LastWhoClass := nil.
+    classes do:[:aClass |
+	|sel|
+
 	sel := aClass class selectorForMethod:self.
 	sel notNil ifTrue:[^ Array with:aClass class with:sel].
     ].