Signed-off-by: Eval EXEC <execvy@gmail.com>

…t, r=WaffleLapkin

Improve document of `unsafe_code` lint

This PR add another `unsafe_code` lint example, want to close rust-lang#111967

…otriddle,lcnr

[rustdoc] List matching impls on type aliases

Fixes rust-lang#32077.

Thanks a lot to ``@lcnr`` who helped me a lot with this fix!

cc ``@notriddle``
r? ``@lcnr``

…icate-region-constraints, r=lcnr

Deduplicate identical region constraints in new solver

the new solver doesn't track whether we've already proven a goal like the fulfillment context's obligation forest does, so we may be instantiating a canonical response (and specifically, its nested region obligations) quite a few times.

This may lead to exponentially gathering up identical region constraints for things like auto traits, so let's deduplicate region constraints when in `compute_external_query_constraints`.

r? ``@lcnr``