do not use the FindContextNode class directly

com.oracle.truffle.r.engine/src/com/oracle/truffle/r/engine/REngine.java

@@ -39,8 +39,8 @@ import com.oracle.truffle.api.frame.Frame;
 import com.oracle.truffle.api.frame.FrameDescriptor;
 import com.oracle.truffle.api.frame.MaterializedFrame;
 import com.oracle.truffle.api.frame.VirtualFrame;
-import com.oracle.truffle.api.impl.FindContextNode;
 import com.oracle.truffle.api.interop.TruffleObject;
+import com.oracle.truffle.api.nodes.Node;
 import com.oracle.truffle.api.nodes.RootNode;
 import com.oracle.truffle.api.profiles.ConditionProfile;
 import com.oracle.truffle.api.profiles.ValueProfile;
@@ -54,13 +54,13 @@ import com.oracle.truffle.r.nodes.builtin.RBuiltinPackages;
 import com.oracle.truffle.r.nodes.builtin.base.printer.ValuePrinterNode;
 import com.oracle.truffle.r.nodes.control.BreakException;
 import com.oracle.truffle.r.nodes.control.NextException;
-import com.oracle.truffle.r.nodes.function.PromiseHelperNode;
 import com.oracle.truffle.r.nodes.function.CallMatcherNode.CallMatcherGenericNode;
+import com.oracle.truffle.r.nodes.function.PromiseHelperNode;
 import com.oracle.truffle.r.nodes.instrumentation.RInstrumentation;
 import com.oracle.truffle.r.runtime.ArgumentsSignature;
+import com.oracle.truffle.r.runtime.ExitException;
 import com.oracle.truffle.r.runtime.FastROptions;
 import com.oracle.truffle.r.runtime.JumpToTopLevelException;
-import com.oracle.truffle.r.runtime.ExitException;
 import com.oracle.truffle.r.runtime.RArguments;
 import com.oracle.truffle.r.runtime.RCaller;
 import com.oracle.truffle.r.runtime.RError;
@@ -301,7 +301,7 @@ final class REngine implements Engine, Engine.Timings {
 
         private final List<RSyntaxNode> statements;
 
-        @SuppressWarnings("unchecked") @Child private FindContextNode<RContext> findContext = (FindContextNode<RContext>) TruffleRLanguage.INSTANCE.actuallyCreateFindContextNode();
+        @Child private Node findContext = TruffleRLanguage.INSTANCE.actuallyCreateFindContextNode();
 
         PolyglotEngineRootNode(List<RSyntaxNode> statements) {
             super(TruffleRLanguage.class, SourceSection.createUnavailable("repl", RSource.Internal.REPL_WRAPPER.string), new FrameDescriptor());
@@ -316,7 +316,7 @@ final class REngine implements Engine, Engine.Timings {
         @Override
         public Object execute(VirtualFrame frame) {
             RContext oldContext = RContext.threadLocalContext.get();
-            RContext newContext = findContext.executeFindContext();
+            RContext newContext = TruffleRLanguage.INSTANCE.actuallyFindContext0(findContext);
             RContext.threadLocalContext.set(newContext);
             try {
                 Object lastValue = RNull.instance;