Adjective + to infinitive vs. gerund

I recall being taught that normally after adjectives we use the "to infinitive": It's easy to say. It's hard to do. But how do the following examples fall into this rule? "It was great talking to you." "It's been nice meeting you."

I've been tutoring students in English as a second language, and I'm failing to find a "simple" justification for the two types of sentences (as, obviously, I am myself struggling to understand).

Very many thanks! Mel.

Solution 1:

In the past, Nice to meet you was considered the proper response to an introduction or short conversation with someone new. But like everything else, language changes and "Nice meeting you" is perfectly acceptable.

Since great is not on the list, there is no reason it can't be followed by a gerund, so, again, you're safe there.

I have not been able to find the rule you gave. However I have found a list of adjectives that require the "to + infinitive". They are:

adjectives expressing emotion, e.g. angry, disappointed, glad, sad, happy, anxious, pleased, surprised, proud, unhappy, confused, befuddled...

adjectives of ability or willingness, e.g. able, unable, due, eager, keen, likely, unlikely, ready, prepared, unwilling, willing...

adjectives used to express opinions, e.g. to give opinions: difficult, easy, possible, impossible, hard, right, wrong, kind, nice, clever, silly, foolish...

adjectives referring to difficulty, e.g. difficult, easy, possible, impossible, hard

when using the preposition "of" with other adjectives:

It’s kind of you to help. It would be silly of him to spend all his money.

This was all I could find. Sorry.

Source: British Council

Solution 2:

You could think of talking to you as being like an adverb:

I had a great time talking to you.

It was great talking to you.

You could, at a stretch, also consider talking to you as being like a noun:

Talking to you was great.

It was great talking to you.

This is non-standard, but many idioms are.

Either way, the same meaning is conveyed, so I don't think there's any need to complicate matters by looking for the "distinction without a difference".