Fix migration of already-wrapped context values

Author: eregon

truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/TruffleContextTest.java

@@ -769,6 +769,31 @@ public void testEvalInnerContext() throws InteropException {
         innerContext.close();
     }
 
+    @Test
+    public void testMigrateInnerContextValueThroughOtherInnerContext() throws InteropException {
+        EvalContextTestObject innerObject = new EvalContextTestObject();
+        EvalContextTestObject forwardingObject = new EvalContextTestObject();
+        AtomicBoolean returnInnerObject = new AtomicBoolean(true);
+        setupLanguageThatReturns(() -> returnInnerObject.getAndSet(false) ? innerObject : forwardingObject);
+
+        TruffleContext innerContext = languageEnv.newInnerContextBuilder().initializeCreatorContext(true).build();
+        TruffleContext otherInnerContext = languageEnv.newInnerContextBuilder().initializeCreatorContext(true).build();
+        innerObject.expectedContext = innerContext;
+        forwardingObject.expectedContext = otherInnerContext;
+
+        Object innerResult = innerContext.evalInternal(null, newTruffleSource());
+        assertNotEquals("must be wrapped", innerObject, innerResult);
+
+        Object forwardingResult = otherInnerContext.evalInternal(null, newTruffleSource());
+        assertNotEquals("must be wrapped", forwardingObject, forwardingResult);
+        InteropLibrary.getUncached().execute(forwardingResult, innerResult);
+
+        assertEquals(1, innerObject.executeCount);
+        assertEquals(1, forwardingObject.executeCount);
+        otherInnerContext.close();
+        innerContext.close();
+    }
+
     @ExportLibrary(InteropLibrary.class)
     static class EvalContextTestObject implements TruffleObject {
 

truffle/src/com.oracle.truffle.polyglot/src/com/oracle/truffle/polyglot/PolyglotContextImpl.java

@@ -1729,7 +1729,7 @@ Object migrateValue(Object value, PolyglotContextImpl valueContext) {
                 // unpack foreign value it belongs to that context
                 return otherValue.delegate;
             } else {
-                return new OtherContextGuestObject(this, otherValue.delegate, valueContext);
+                return new OtherContextGuestObject(this, otherValue.delegate, otherValue.delegateContext);
             }
         }
         assert value instanceof TruffleObject;