@Override
      public void beforeValueReturn(@NotNull DfaValue value,
                                    @Nullable PsiExpression expression,
                                    @NotNull PsiElement context,
                                    @NotNull DfaMemoryState state) {
        if (context == owner && expression != null) {
          DfaNullability nullability = DfaNullability.fromDfType(state.getDfType(value));
          if (TypeConversionUtil.isPrimitiveAndNotNull(expression.getType()) || 
              nullability == DfaNullability.NOT_NULL) {
            hasNotNulls = true;
          }
          else if (nullability == DfaNullability.NULL) {
            hasNulls = true;
          }
          else if (nullability == DfaNullability.NULLABLE) {
            hasNulls = hasNotNulls = true;
          }
          else {
            hasUnknowns = true;
          }
        }
      }
@Override
      public void beforeValueReturn(@NotNull DfaValue value,
                                    @Nullable PsiExpression expression,
                                    @NotNull PsiElement context,
                                    @NotNull DfaMemoryState state)