Position of adverb "implicitly"

In the following sentence I'm not sure where to put implicitly:

The language doesn't support Int and ^(implicitly) converts ^(implicitly) Int to Double ^(implicitly).

First I put it at the end, because I learned:

The man drove the car carefully.

But somehow it sounds strange: converts Int to Double implicitly.

Most natural to my ears is implicitly at position two so I would place it there, although comparing "convert implicitly" to "implicitly convert" indicate to put it at the first place (Same for converts (with s)). But most Google hits show its use with cannot, should, ..., so I'm unsure which one is correct in my example above.

Which one is correct and why?

The language doesn't support Int and implicitly converts Int to Double.

The language doesn't support Int and converts Int to Double implicitly.

Both sentences sound natural and are grammatically correct. Implicitly is an adverb and as such it modifies the verb. You can place it right before the main verb in a sentence, but not between the verb and its object. That's why a native speaker wouldn't normally say *converts implicitly Int to Double. As for the position of the adverb at the end of the sentence, it is natural because it is close enough to the verb to make the meaning clear.

As @Irene says, two of the three are grammatically correct, but they read with significantly different emphasis.

If you want to focus mainly on the action, mention it first, then specify how it will be done.
This way, the sentence almost reads the same as if you'd left off the modifier:

The language doesn't support Int and converts Int to Double implicitly.
The man drove the car carefully.

Alternatively, if you want to draw attention to how the action is done, preface the action with the adverb, inseparably tying the two together:

The language doesn't support Int and implicitly converts Int to Double.
The man carefully drove the car.

It depends on how important the "implicit" portion is. If you don't want it to be glossed over or lost when someone is scanning the text, pair it with the verb.

When adverbs modify verbs, they can usually be moved around the sentence though there is an exception with the adverbs merely and only (and others like them). When an adverb modifies another adverb or an adjective, it must be place directly in front of the word it modifies.