is "child" without "a" correct in this sentence?

He was still child enough to run along with the group.

Is this sentence grammatically correct?


Solution 1:

He was still child enough to run along with the group.

It is an idiom.

I was fool enough to dive into the water.

He was hero enough to save the drowning kitten.

It is correct because "child" acts as an adjective here.

Compare:

He was still young enough to run along with the group.