# Enabling the next-generation trait solver on nightly

DevFeed: [Enabling the next-generation trait solver on nightly](<https://devfeed.tech/articles/enabling-the-next-generation-trait-solver-on-nightly-2350.md>)

Original publisher: [Read original article](<https://blog.rust-lang.org/2026/08/21/enabling-next-solver-on-nightly/>)

Author: lcnr

Published: 2026-08-21T00:00:00Z

Content type: article

Language: en

Sources: [Rust Blog](<https://devfeed.tech/sources/rust-blog.md>)

Topics: [toolchain](<https://devfeed.tech/topics/toolchain.md>)

Tags: [bugs](<https://devfeed.tech/tags/bugs.md>), [diagnostics](<https://devfeed.tech/tags/diagnostics.md>), [inference](<https://devfeed.tech/tags/inference.md>), [performance](<https://devfeed.tech/tags/performance.md>), [rust](<https://devfeed.tech/tags/rust.md>), [types](<https://devfeed.tech/tags/types.md>)

## AI overview

Rust is enabling its next-generation trait solver by default on nightly ahead of planned stabilization. The compiler-internal replacement changes trait and associated-type handling, fixes many known issues, and needs testing for breakage, performance regressions, and diagnostics.

## Source excerpt

After nearly 4 years of active development, the next-generation trait solver is close to stabilization. We are enabling it by default on nightly to surface any remaining issues and plan to stabilize it in the next months. This is the largest single change to the Rust compiler since its initial release. It completely replaces how we prove where-clauses, normalize associated types, and much more. Please try out the latest nightly and open an issue if you encounter any bugs or regressions. This is an internal component of the compiler. The main benefits of this rework will come in the future. The removal of the old implementation will unblock features such as Type Alias Impl Trait and Return Type Notation, allow us to add new implicit default trait bounds (e.g., Move and Forget), and enable us to fix the remaining type system unsoundnesses. Even so, this already fixes a huge number of issues. As an underapproximation, we currently know of more than 200 issues on GitHub fixed by this change. This also has a significant impact on compile times; more on that later. When developing on nightly, you may accidentally rely on behavior only supported by the new trait solver. This is an incredibly big change which results in a non-trivial amount of breakage. Most of these changes are intended improvements to type inference or the removal of undesirable behavior. We are tracking the known issues and breakage in a pinned GitHub issue. What can I do? Please update to the latest nightly version by using rustup update nightly and use it to test your existing projects and libraries. Please tell us if you encounter any breakage, compile-time performance regression, or bad diagnostics. We have not yet spent too much time on error messages for the next-generation trait solver, so we would also appreciate you using this nightly for development to find poor diagnostics and other bugs in our error handling. If you encounter any issue, take a quick look at the pinned GitHub issue to see if t