Trait EvalContextFamily 

pub trait EvalContextFamily: 'static {
    type Context<'a>;
}

A “family” of evaluation context types, parameterized by lifetime.

This trait uses Generic Associated Types (GATs) to separate the context family (known at parse time, carries no lifetime) from the concrete context type (instantiated with a lifetime at execution time).

Why a family?

The parser is long-lived and created once, but contexts are short-lived and often borrow data. We can’t write Parser<MyContext<'a>> because 'a doesn’t exist when the parser is created. Instead, the parser stores the family F, and F::Context<'a> is only materialized when execute is called.

Example

struct SpanFamily;

impl EvalContextFamily for SpanFamily {
    type Context<'a> = SpanContext<'a>;
}

struct SpanContext<'a> {
    span: &'a mut Span,
    resource: &'a Resource,
}

Required Associated Types

type Context<'a>

The concrete context type for a given borrow lifetime.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors