User types should support a static "factory" method which is called automatically for default initialization.

[JalonSolov]

Discord discussion starts here: https://discord.com/channels/592103645835821068/592106336838352923/1272226772951367791

The idea is that if a user type (struct, sum type, alias, etc.) has a static method with a particular name (which could be new, init, or whatever), this method will be called when assigning a default value.

For example, right now, if you have a struct like this

struct MyStruct {
    my_field int
}

then instantiate that struct with a simple

s := MyStruct{}

then my_field will be assigned a value of 0.

You can currently change the default by explicitly assigning a default value, such as

struct MyStruct {
    my_field int = 7
}

in which case

s := MyStruct{}

will should my_field with a value of 7.

This is fine for simple assignments, but if you want something more complex (especially with a struct with more fields, perhaps the values of some rely on the values set for others, etc.), a static "factory" method would make more sense.

The main problem with a static "factory" method currently is that the user both has to know it exists, and has to explicitly call it.

If the compiler would call it automatically when a type is instantiated, this would resolve that issue. If the static method didn't exist, then the current default 0 would still apply.

Thoughts?

[blackshirt]

The main problem with a static "factory" method currently is that the user both has to know it exists, and has to explicitly call it.

If the compiler would call it automatically when a type is instantiated, this would resolve that issue. If the static method didn't exist, then the current default 0 would still apply.

I think its good to have static factory explicitly called by user with predefined behaviour ....and fallback to default value with default behaviour of instantiated factory