<a name="std_internal"></a>

Module std::internal

Defines the <code><a href="../std/internal.md#std_internal_Permit">Permit</a></code> 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 <code><a href="../std/internal.md#std_internal_Permit">Permit</a></code>, 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
• Function permit

<a name="std_internal_Permit"></a>

Struct Permit

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

<a name="std_internal_permit"></a>

Function permit

Construct a new <code><a href="../std/internal.md#std_internal_Permit">Permit</a></code> for the type <code>T</code>. Can only be called by the module that defines the type <code>T</code>.