Gpbits must be propagated to copies.

com.oracle.truffle.r.runtime/src/com/oracle/truffle/r/runtime/data/RFunction.java

@@ -138,6 +138,7 @@ public final class RFunction extends RSharingAttributeStorage implements RTypedV
             }
             newFunction.initAttributes(newAttributes);
         }
+        newFunction.gpbits = gpbits;
         return newFunction;
 
     }

com.oracle.truffle.r.runtime/src/com/oracle/truffle/r/runtime/data/RS4Object.java

@@ -55,6 +55,7 @@ public class RS4Object extends RSharingAttributeStorage {
                 newAttributes.put(attr.getName(), attr.getValue());
             }
         }
+        resultS4.gpbits = gpbits;
         return resultS4;
 
     }

com.oracle.truffle.r.test/src/com/oracle/truffle/r/test/library/base/TestSimpleAttributes.java

@@ -161,5 +161,7 @@ public class TestSimpleAttributes extends TestBase {
         assertEval("{ x<-matrix(1, ncol=1); y<-c(1,2,3,4); x*y }");
 
         assertEval("{ x<-c(1,2); attr(x, \"foo\")<-\"foo\"; y<-x; attributes(y)<-NULL; x }");
+
+        assertEval("{ gen<-function(object) 0; setGeneric(\"gen\"); x<-gen; attr(x, \"valueClass\")<-character(); isS4(x) }");
     }
 }