code: private void checkReferenceEquality(Node n, String typeName, String fileName) {
      if (n.getToken() == Token.SHEQ
          || n.getToken() == Token.EQ
          || n.getToken() == Token.SHNE
          || n.getToken() == Token.NE) {
        JSType firstJsType = n.getFirstChild().getJSType();
        JSType lastJsType = n.getLastChild().getJSType();
        boolean hasType = isType(firstJsType, fileName) || isType(lastJsType, fileName);
        boolean hasNullType = isNullType(firstJsType) || isNullType(lastJsType);
        if (hasType && !hasNullType) {
          compiler.report(JSError.make(n, J2CL_REFERENCE_EQUALITY, typeName));
        }
      }
    }
docs: Reports an error if the node is a reference equality check of the specified type.