Attribute Macro default_impl 

#[default_impl]

Generates the missing default implementations for the traits provided by OpenZeppelin Stellar library.

#[contractimpl] macro requires all the default implementations to be provided under the code block:

#[contractimpl]
impl Trait for MyContract {
    /*
        The client generated by the `#[contractimpl]` macro will have access only
        to the methods specified in here. Which means, if you do not provide the
        default implementations of the methods, the client generated by the
        `#[contractimpl]` macro won't have access to those methods.

        This is due to how macros work in Rust. They cannot access the default
        implementations of the methods of this trait, since they are not in the
        scope of the macro.

        To overcome this, we provide a macro for our traits, that generates the
        missing default implementations for the methods of the trait, so
        you can only focus on the overrides, and leave the default implementations
        out as per usual.
    */
}

Example:

#[default_impl] // IMPORTANT: place this above `#[contractimpl]`
#[contractimpl]
impl NonFungibleToken for MyContract {
    /* your overrides here */
}

This macro works for the following traits:

• FungibleToken
• FungibleBurnable
• NonFungibleToken
• NonFungibleBurnable
• NonFungibleEnumerable
• AccessControl
• Ownable

Notes

This macro does not support the below traits on purpose:

• FungibleAllowList
• FungibleBlockList
• NonFungibleRoyalties

Because, there are no default implementation to enforce how the authorization should be configured. Not providing a default implementation for these traits is a reminder for the implementor to provide the authorization logic for these traits.