compiler.tree.dead-code: methods on flushable generics should be flushable

basis/compiler/tree/cleanup/cleanup-tests.factor

@@ -6,6 +6,7 @@ definitions system layouts vectors math.partial-dispatch
 math.order math.functions accessors hashtables classes assocs
 io.encodings.utf8 io.encodings.ascii io.encodings fry slots
 sorting.private combinators.short-circuit grouping prettyprint
+generalizations
 compiler.tree
 compiler.tree.combinators
 compiler.tree.cleanup
@@ -518,3 +519,23 @@ cell-bits 32 = [
     [ { integer integer } declare + drop ]
     { + +-integer-integer } inlined?
 ] unit-test
+
+[ [ ] ] [
+    [
+        20 f <array>
+        [ 0 swap nth ] keep
+        [ 1 swap nth ] keep
+        [ 2 swap nth ] keep
+        [ 3 swap nth ] keep
+        [ 4 swap nth ] keep
+        [ 5 swap nth ] keep
+        [ 6 swap nth ] keep
+        [ 7 swap nth ] keep
+        [ 8 swap nth ] keep
+        [ 9 swap nth ] keep
+        [ 10 swap nth ] keep
+        [ 11 swap nth ] keep
+        [ 12 swap nth ] keep
+        14 ndrop
+    ] cleaned-up-tree nodes>quot
+] unit-test

basis/compiler/tree/dead-code/simple/simple.factor

@@ -1,7 +1,7 @@
 ! Copyright (C) 2008 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
 USING: kernel accessors words assocs sequences arrays namespaces
-fry locals definitions classes.algebra
+fry locals definitions classes classes.algebra generic
 stack-checker.state
 stack-checker.backend
 compiler.tree
@@ -9,8 +9,13 @@ compiler.tree.propagation.info
 compiler.tree.dead-code.liveness ;
 IN: compiler.tree.dead-code.simple
 
-: flushable? ( word -- ? )
-    [ "flushable" word-prop ] [ "predicating" word-prop ] bi or ;
+GENERIC: flushable? ( word -- ? )
+
+M: predicate flushable? drop t ;
+
+M: word flushable? "flushable" word-prop ;
+
+M: method-body flushable? "method-generic" word-prop flushable? ;
 
 : flushable-call? ( #call -- ? )
     dup word>> dup flushable? [