Minor fixes in MakeNames and S3 dispatch

Author: steve-s

com.oracle.truffle.r.nodes.builtin/src/com/oracle/truffle/r/nodes/builtin/base/MakeNames.java

@@ -117,7 +117,7 @@ private static NewNames updateNewNames(RAbstractStringVector names, VectorReuse
         NewNames nn = newNames;
         if (nn == null) {
             RAbstractStringVector res = reuse.getResult(names);
-            VectorAccess access = reuse.access(res);
+            VectorAccess access = res.slowPathAccess();
             VectorAccess.RandomIterator iter = access.randomAccess(res);
             nn = new NewNames(res, access, iter);
         }

com.oracle.truffle.r.nodes.builtin/src/com/oracle/truffle/r/nodes/builtin/base/S3DispatchFunctions.java

@@ -239,6 +239,7 @@ public abstract static class NextMethod extends RBuiltinNode.Arg3 {
         private final ConditionProfile genericCallFrameNullProfile = ConditionProfile.createBinaryProfile();
         private final ConditionProfile genericDefFrameNullProfile = ConditionProfile.createBinaryProfile();
         private final ConditionProfile alternateClassHeaderProfile = ConditionProfile.createBinaryProfile();
+        private ConditionProfile needToBoxStringProfile = ConditionProfile.createBinaryProfile();
 
         private final ValueProfile parameterSignatureProfile = ValueProfile.createIdentityProfile();
         private final ValueProfile suppliedParameterSignatureProfile = ValueProfile.createIdentityProfile();
@@ -321,10 +322,17 @@ private RStringVector readType(VirtualFrame frame) {
             if (alternateClassHeaderProfile.profile(storedClass == null || storedClass == RNull.instance)) {
                 return getAlternateClassHr(frame);
             } else {
-                return (RStringVector) storedClass;
+                return boxString(storedClass);
             }
         }
 
+        private RStringVector boxString(Object value) {
+            if (needToBoxStringProfile.profile(value instanceof String)) {
+                return RDataFactory.createStringVector((String) value);
+            }
+            return (RStringVector) value;
+        }
+
         private RStringVector getAlternateClassHr(VirtualFrame frame) {
             if (promiseHelper == null) {
                 CompilerDirectives.transferToInterpreterAndInvalidate();