Rust 2.0 introduces a thought experiment on safe specialization, a long-awaited feature that has faced numerous stabilization challenges. Specialization in Rust aims to optimize operations, such as cloning a `Vec<T>`, by exploiting specific type traits like `Copy`. For instance, when `T` implements `Copy`, the cloning process can bypass element-wise iteration and use `memcpy` for efficient bulk-copying.

The current nature of trait resolution in Rust involves eager binding, where the compiler immediately selects the most specific implementation, leading to potential incoherence. This is evident in scenarios where a generic function like `use_fizz` is used with different types, resulting in disparate behaviors. To address these issues, the proposal suggests a 'grounded' approach, where the compiler resolves implementations only when types are fully known, thus ensuring soundness.

This method introduces a new keyword, `final impl`, which allows the compiler to eagerly bind implementations that are definitive and unchangeable, improving ergonomics for structural types. Additionally, the concept of ranking implementations is explored to resolve ambiguities, where lower-ranking implementations are prioritized. These innovations, while promising, present challenges in maintaining backward compatibility, as they would require significant changes to existing codebases, particularly in the standard library.

The evolution of Rust towards safe specialization represents a significant step in enhancing the language's performance and expressiveness, though it requires careful consideration of soundness and compatibility.