Angular error – can’t resolve all parameters for []

The error is as follows:

This problem has been a headache for a long time. Several reasons can be summarized as follows:

However, these two methods failed to solve my problem, and another reason was finally found, that is, the parameter that cannot be resolved is an HTTPService. The service was exported twice in index.ts, and one of them was commented out, so the error was not reported. In fact, this may only be the surface cause, but the root cause remains to be studied

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