Fix step-into on generic words and call-next-method in walker

core/generic/standard/standard-tests.factor

@@ -309,3 +309,11 @@ M: xref-tuple-2 xref-test (xref-test) ;
     \ xref-test
     \ xref-tuple-2 \ xref-test method [ usage unique ] closure key?
 ] unit-test
+
+[ t ] [
+    { } \ nth effective-method nip \ sequence \ nth method eq?
+] unit-test
+
+[ t ] [
+    \ + \ nth effective-method nip dup \ nth "default-method" word-prop eq? and
+] unit-test

core/generic/standard/standard.factor

@@ -105,7 +105,9 @@ ERROR: no-next-method class generic ;
     ] [ ] make ;
 
 : single-effective-method ( obj word -- method )
-    [ order [ instance? ] with find-last nip ] keep method ;
+    [ [ order [ instance? ] with find-last nip ] keep method ]
+    [ "default-method" word-prop ]
+    bi or ;
 
 TUPLE: standard-combination # ;
 

extra/tools/walker/walker-tests.factor

@@ -1,6 +1,7 @@
 USING: tools.walker io io.streams.string kernel math
 math.private namespaces prettyprint sequences tools.test
-continuations math.parser threads arrays tools.walker.debug ;
+continuations math.parser threads arrays tools.walker.debug
+generic.standard ;
 IN: tools.walker.tests
 
 [ { } ] [
@@ -97,6 +98,9 @@ IN: tools.walker.tests
 [ { 6 } ]
 [ [ [ 3 throw ] [ 2 * ] recover ] test-walker ] unit-test
 
+[ { T{ no-method f + nth } } ]
+[ [ [ 0 \ + nth ] [ ] recover ] test-walker ] unit-test
+
 [ { } ] [
     [ "a" "b" set "c" "d" set [ ] test-walker ] with-scope
 ] unit-test

extra/tools/walker/walker.factor

@@ -83,6 +83,9 @@ M: object add-breakpoint ;
 : (step-into-continuation) ( -- )
     continuation callstack >>call break ;
 
+: (step-into-call-next-method) ( class generic -- )
+    next-method-quot (step-into-quot) ;
+
 ! Messages sent to walker thread
 SYMBOL: step
 SYMBOL: step-out
@@ -132,6 +135,7 @@ SYMBOL: +stopped+
     { if [ (step-into-if) ] }
     { dispatch [ (step-into-dispatch) ] }
     { continuation [ (step-into-continuation) ] }
+    { (call-next-method) [ (step-into-call-next-method) ] }
 } [ "step-into" set-word-prop ] assoc-each
 
 {