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Module std::internal

Defines the 

Permit
type, which can be used to constrain the logic of a generic function to be authorized only by the module that defines the type parameter.

module example::use_permit;

public struct MyType { /* ... */ }

public fun test_permit() {
let permit = internal::permit<MyType>();
/* external_module::call_with_permit(permit); */
}

To write a function that is guarded by a 

Permit
, require it as an argument.

// Silly mockup of a type registry where a type can be registered only by
// the module that defines the type.
module example::type_registry;

public fun register_type<T>(_: internal::Permit<T> /* ... */) {
/* ... */
}

Struct Permit​

A privileged witness of the T type. Instances can only be created by the module that defines the type T.

public struct Permit<phantom T> has drop
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Fields

Function permit​

Construct a new 

Permit
for the type T. Can only be called by the module that defines the type T.

public fun permit<T>(): std::internal::Permit<T>
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Implementation
public fun permit<T>(): Permit<T> { Permit() }