Invalidate the "no CharSXP vectors" assumption in RStringVector ctor if appropriate

Author: steve-s

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

@@ -46,12 +46,14 @@ public final class RStringVector extends RVector<Object[]> implements RAbstractS
 
     private static final Assumption noWrappedStrings = Truffle.getRuntime().createAssumption();
 
-    private long nativeContentsAddr;
     private Object[] data;
 
     RStringVector(Object[] data, boolean complete) {
         super(complete);
         assert data instanceof String[] || data instanceof CharSXPWrapper[];
+        if (noWrappedStrings.isValid() && data instanceof CharSXPWrapper[]) {
+            noWrappedStrings.invalidate();
+        }
         this.data = data;
         assert RAbstractVector.verify(this);
     }

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

@@ -791,13 +791,7 @@ public final String toString() {
     }
 
     protected boolean canBeValidStore(Object store, Object data) {
-        RContext ctx;
-        try {
-            ctx = RContext.getInstance();
-        } catch (IllegalStateException ex) {
-            return true; // no context, we cannot check anything
-        }
         // We can be only sure if there is only one thread
-        return !ctx.isSingle() || store == data;
+        return !RContext.isSingle() || store == data;
     }
 }