…`ForeignItem`

but right now all of them have zero const generic params

Turn `is_val_statically_known` into such an intrinsic to demonstrate. It is perfectly safe to call after all.

The check within changed from `delay_span_bug` to `delay_good_path_bug`
in rust-lang#110476, and removing the check altogether was considered. It's a
very weak sanity check and gets in the way of removing good path delayed
bugs altogether, so this PR just removes it.

It's only has a single remaining purpose: to ensure that a diagnostic is
printed when `trimmed_def_paths` is used. It's an annoying mechanism:
weak, with odd semantics, badly named, and gets in the way of other
changes.

This commit replaces it with a simpler `must_produce_diag` mechanism,
getting rid of a diagnostic `Level` along the way.

…r, r=Amanieu

Add `A: 'static` bound for `Arc/Rc::pin_in`

Analogous to rust-lang#79327
Needed to preserve pin's [drop guarantee](https://doc.rust-lang.org/std/pin/index.html#drop-guarantee)

…r=dtolnay

Use generic `NonZero` internally.

Tracking issue: rust-lang#120257

Implement intrinsics with fallback bodies

fixes rust-lang#93145 (though we can port many more intrinsics)
cc rust-lang#63585

The way this works is that the backend logic for generating custom code for intrinsics has been made fallible. The only failure path is "this intrinsic is unknown". The `Instance` (that was `InstanceDef::Intrinsic`) then gets converted to `InstanceDef::Item`, which represents the fallback body. A regular function call to that body is then codegenned. This is currently implemented for

* codegen_ssa (so llvm and gcc)
* codegen_cranelift

other backends will need to adjust, but they can just keep doing what they were doing if they prefer (though adding new intrinsics to the compiler will then require them to implement them, instead of getting the fallback body).

cc `@scottmcm` `@WaffleLapkin`

### todo

* [ ] miri support
* [x] default intrinsic name to name of function instead of requiring it to be specified in attribute
* [x] make sure that the bodies are always available (must be collected for metadata)

…rors

Be less confident when `dyn` suggestion is not checked for object safety

rust-lang#120275 no longer checks bare traits for object safety when making a `dyn` suggestion on Rust < 2021. In this case, qualify the suggestion with a note that the trait must be object safe, to prevent user confusion as seen in rust-lang#116434

r? `@fmease`

…r=dtolnay

Make `NonZero::get` generic.

Tracking issue: rust-lang#120257

Depends on rust-lang#120521.

r? `@dtolnay`

…errors

Continue compilation after check_mod_type_wf errors

The ICEs fixed here were probably reachable through const eval gymnastics before, but now they are easily reachable without that, too.

The new errors are often bugfixes, where useful errors were missing, because they were reported after the early abort. In other cases sometimes they are just duplication of already emitted errors, which won't be user-visible due to deduplication.

fixes rust-lang#120860

Remove good path delayed bugs

Because they're not that useful, and kind of annoying. Details in the individual commits.

r? `@compiler-errors`