new solver: prefer trivial builtin impls by lqd · Pull Request #135639 · rust-lang/rust (original) (raw)

As discussed on zulip, this PR:

• adds a new BuiltinImplSource::Trivial source, and marks the Sized builtin impls as trivial
• prefers these trivial builtin impls in merge_trait_candidates

The comments can likely be wordsmithed a bit better, and I stole was inspired by the old solver ones. Let me know how you want them improved.

When enabling the new solver for tests, 3 UI tests now pass:

• regions/issue-26448-1.rs and its sibling regions/issue-26448-2.rs were rejected by the new solver but accepted by the old one
• and issues/issue-42796.rs where the old solver emitted some overflow errors in addition to the expected error

(For some reason one of these tests is run-pass, but I can take care of that another day)

r? lcnr