Trait Engine 

pub trait Engine:
    Debug
    + Send
    + Sync {
    // Required methods
    fn name(&self) -> &str;
    fn fold(&self, layers: &[Layer<'_>]) -> Result<Folded, Error>;
}

A fold, and where each leaf came from.

Implement this to resolve with something else entirely — a backend this crate does not ship, or a rule of your own. Two things are asked of an implementation, and the rest is its business:

• Precedence is the argument’s order. layers[0] is the lowest.
• A tag is reported only for a leaf that layer actually supplied.

Errors

A fold can fail — a backend may refuse a key shape of its own — and the error reaches the caller as an ordinary load failure. It must not carry a configuration value: an engine that puts one in a message breaks the contract every other part of this crate keeps.

Required Methods

fn name(&self) -> &str

What to call this engine in a diagnostic.

fn fold(&self, layers: &[Layer<'_>]) -> Result<Folded, Error>

Folds layers, lowest precedence first.

Errors

If the backend refuses the shape it was handed.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors