Do not generate nullable types when converting "instanceof" to "is"

j2k/src/org/jetbrains/jet/j2k/visitors/ExpressionVisitor.java

@@ -192,9 +192,10 @@ public class ExpressionVisitor extends StatementVisitor {
     @Override
     public void visitInstanceOfExpression(@NotNull PsiInstanceOfExpression expression) {
         super.visitInstanceOfExpression(expression);
-        myResult = new IsOperator(
-                getConverter().expressionToExpression(expression.getOperand()),
-                getConverter().elementToElement(expression.getCheckType()));
+
+        TypeElement typeElement = (TypeElement) getConverter().elementToElement(expression.getCheckType());
+        typeElement.getMyType().convertedToNotNull();
+        myResult = new IsOperator(getConverter().expressionToExpression(expression.getOperand()), typeElement);
     }
 
     @Override

j2k/tests/testData/ast/isOperator/expression/complicatedExpression.kt

@@ -1 +1 @@
-(c.getType().getName() is String?)
+(c.getType().getName() is String)

j2k/tests/testData/ast/isOperator/expression/simpleReference.kt

@@ -1 +1 @@
-(a is String?)
+(a is String)