type-equalities

The central type, TypeEq<_, _>, allows for zero-overhead, safe value coercions and is itself zero-sized. Further, naming TypeEq<T, U> is well-formed for any types, but an inhabitant is available only if the equality holds. For trait-level type equality, T: IsEqual<U> can be used.

The zero overhead claim can be seen in the provided benchmarks:

let eq = refl::<u32>().lift_through::<SliceF<BENCH_LEN>>();
// b.iter(|| [0; BENCH_LEN]);         // bench_no_coerce
b.iter(|| eq.coerce([0; BENCH_LEN])); // bench_coerce_array_refl

> running 2 tests
test benches::bench_no_coerce         ... bench:      10,665 ns/iter (+/- 695)
test benches::bench_coerce_array_refl ... bench:      10,776 ns/iter (+/- 1,004)

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT) at your option.

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