1.38 beta fails to bootstrap itself

[Keruspe]

When using 1.38 beta to bootstrap itself, I get:

error: unnecessary `unsafe` block
   --> src/bootstrap/builder.rs:148:19
    |                    
148 |             name: unsafe { ::std::intrinsics::type_name::<S>() },
    |                   ^^^^^^ unnecessary `unsafe` block
    |                  

[Mark-Simulacrum]

This is expected and not a supported bootstrapping configuration; if you want to not see these errors you'll want to either bootstrap with N-1 compiler (so, in this case, 1.37) or I believe remove deny(warnings) from bootstrap and some other libraries, as well as set deny-warnings in config.toml to false. Note that only the 1.37 bootstrap method is officially supported as "guaranteed to work", the deny warnings fix is more of a hack. Closing as won't fix.

[Keruspe]

@Mark-Simulacrum Huh? In the past this was always fixed as it's a very common practice for distribution packaging (I don't know of a single packager not doing that).

See e.g. #54322 or #60265 (in which you sort of acknowledged that yourself)

deny-warnings is already set to false in config.toml, so I guess it somehow doesn't apply to building bootstrap itself.

[Keruspe]

I hope #63941 is an acceptable compromise wrt this. Thanks for pointing out the deny-warnings option which I forgot (since it has been set to false forever for us and never had any effect on the build of bootstrap itself)

[Mark-Simulacrum]

Yeah #63941 is great; in this case the unsafe block is needed for 1.37 but not on 1.38; if there was an easy way to support both use cases then I'd be happy to accept a PR targeting beta but I'm not personally aware of one -- it looks like we don't seem to have an #[allow(unused_unsafe)] or similar?

We try to support distros and such where possible in this configuration, it's just that this specific case I'm not sure how much we can do. deny-warnings=false is always my recommendation when using a different bootstrap compiler, or manual patches to the code.