[move][adapter] Static init rules

[tnowacki]

• Made init rules static
• The existence of the function is optional
• The function must be named 'init'
• The function must be private
• The function can have a single parameter, &mut TxContext
• Alternatively, the function can have zero parameters

[tnowacki]

See #1323

[lxfind]

Cool! Thank you for taking on this!
A few questions for discussion:

1. Would a more irregular name help distinguish it? like _ _ init _ _?
2. Why not public? Now that we can verify it statically, we can make it public, and not allow anyone making function calls to any function with this name except in tests. This will make it easier to write tests.

[awelc]

2. Why not public? Now that we can verify it statically, we can make it public, and not allow anyone making function calls to any function with this name except in tests. This will make it easier to write tests.

The intention was to emphasize the fact that this is not a "regular" (callable) function.

[lxfind]

The intention was to emphasize the fact that this is not a "regular" (callable) function.

Well, private function only constrains other non-friend modules from calling it. You can still call it from within and friend modules. So I think a verifier that forbids calling it is needed anyway. If so, we can make it public

[awelc]

A general comment. At least part of the reason that this was not implemented in the verifier is that when talking to @sblackshear, we were not sure if init should be treated as (practically) a keyword for function naming (a function called init MUST be a module initializer). On the one hand, this makes things more explicit, and on the other - it is somewhat restrictive from programmer's perspective. I am totally cool with the stricter solution, though.

[tnowacki]

I feel fine basically keywordifying it for Sui move.

Why not public? Now that we can verify it statically, we can make it public, and not allow anyone making function calls to any function with this name except in tests. This will make it easier to write tests.

It is annoying... but you could always do something like #[test_only] public fun call_init() { init() }

not allow anyone making function calls to any function with this name except in tests.

More on this part, this this rule already in place?
That is, should there be a rule that no one can call init functions? Is that rule already in place?
If not, it will make a followup PR

[lxfind]

More on this part, this this rule already in place? That is, should there be a rule that no one can call init functions? Is that rule already in place? If not, it will make a followup PR

No there isn't. But I think we should have it?

[tnowacki]

I'll land this, with a followup for a "don't call init" init rule