static CallHandler<CallChainSimplification> handler() {
      return CallHandler.of(MAP_TO_OBJ, call -> {
        PsiExpression arg = call.getArgumentList().getExpressions()[0];
        PsiType type = StreamApiUtil.getStreamElementType(call.getType());
        PsiClass targetClass = PsiUtil.resolveClassInClassTypeOnly(type);
        if (targetClass == null) return null;
        PsiExpression qualifier = call.getMethodExpression().getQualifierExpression();
        if (qualifier == null ||
            !TypeConversionUtil.boxingConversionApplicable(StreamApiUtil.getStreamElementType(qualifier.getType()), type) ||
            !isBoxingFunction(arg, targetClass)) {
          return null;
        }
        return new ReplaceWithBoxedFix();
      });
    }
static CallHandler<CallChainSimplification> handler()