How to constrain arguments cannot be anonymous function at compile time

[Silentdoer]

for example:

void submit(Function task) {
}

Task is not allowed to be an anonymous function, because it does not have a static lifecycle, so it cannot be sent to other isolates, So how do we prevent users from using anonymous functions at compile time?

[Levi-Lesches]

Do you mean you want task to be a compile-time constant? That would be #1684. I suggest you write there explaining why you would need this because IIRC they're having a hard time justifying the need for it.

[Silentdoer]

What I mean is that user cannot pass a closure to the task(such as (a) => 8), because closure can not as message send to other isolate to exec

[Levi-Lesches]

Right, essentially this:

class Task {const Task(void Function() callback);}
void temp() { }

const Task a = Task(temp);  // works, because we use an existing function
const Task b = Task(() => print("Hello"));  // closures aren't constant

[Silentdoer]

Right, essentially this:

class Task {const Task(void Function() callback);}
void temp() { }

const Task a = Task(temp);  // works, because we use an existing function
const Task b = Task(() => print("Hello"));  // closures aren't constant

Can detection only be used for construction methods?

[Levi-Lesches]

Sorry, what do you mean by construction methods? Class constructors? You can't specify that a constructor can only accept const parameters, but if you try creating a const object (using a const constructor), you'd only be able to pass in a const parameter.

class Task {const Task(void Function() callback);}
void temp() { }

const Task a = Task(temp);  // works, because we use an existing function
final Task b = Task(() => print("Hello"));  // works because b isn't const