fear to do VS fear doing
I learnt that the verb 'fear' can be followed by either supine(to+verb) or gerund(~ing). They are all correct, meaning the same.

So I made the following sentence:
a. I feared to enter the room.
b. I feared entering the room.

However, when I asked other English native speakers if the usages of the both sentences above were correct,
they said only B was correct, and A should be "I'm afraid to enter the room."
Please help to clear up my confusion.

Question

fear to do VS fear doing
I learnt that the verb 'fear' can be followed by either supine(to+verb) or gerund(~ing). They are all correct, meaning the same.

So I made the following sentence:
a. I feared to enter the room.
b. I feared entering the room.

However, when I asked other English native speakers if the usages of the both sentences above were correct,
they said only B was correct, and A should be "I'm afraid to enter the room."
Please help to clear up my confusion.

Answer

Not an English teacher, but I will take a go at it.

The first sentence is definitely incorrect. --- but now I reread and see Andrews answer, I am not so sure.

Fear is a transitive verb. It needs to act upon a noun. That means you can't put another infinitive verb (with to) next.  If you put a gerund on the end (-ing), then the verb has become a noun and it works.

The correction you were given uses the main verb to be (I'm->I am) so that is why it works.

I hope that this helps.

Answer

Both are technically correct. A is far less common however, because infinitives sound abstract in spoken English, thus why most native speakers would say that B is correct - A is fine though, just not really used.

Answer

I don't know that it's incorrect but it just sounds weird, bro. That said I don't see how I could argue that fear should be different from other verbs in the past tense like wanted, needed wished, desired, etc. So I would like that an English teacher could say something about this, also.