Repository: rust
Issue: Tracking Issue for `bare_link_kind`
Labels: A-linkage,O-windows,T-lang,T-compiler,S-waiting-on-team,C-tracking-issue,S-blocked

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This is spun off from RFC 1717 (rust-lang/rfcs#1717) which is already implemented for `#[link(name = "...", kind = "dylib")]`
The feature gate for the issue is `#![feature(bare_link_kind)]`.

### Summary

rust-lang/rfcs#1717 implemented `dllimport` semantics for Windows externs (see the RFC for details). That is, it tells codegen to mark an item as being imported from a DLL:

```rust
// kind is "dylib" so dllimport applied to BAR and baz
#[link(name="foo", kind="dylib")]
extern {
    static BAR: u32;
    fn baz();
}
```

This tracking issue is for applying dllimport without knowing the lib name. E.g.:

```rust
// the lib is supplied separately
// via a build script, the command line, an external build system or even just a separate extern block.
#[link(kind = "dylib")]
extern {
    static BAR: u32;
    fn baz();
}
```

Only "dylib" and "static" kinds are allowed to be used without supplying a name.

### About tracking issues

Tracking issues are used to record the overall progress of implementation.
They are also used as hubs connecting to other relevant issues, e.g., bugs or open design questions.
A tracking issue is however *not* meant for large scale discussion, questions, or bug reports about a feature.
Instead, open a dedicated issue for the specific matter and add the relevant feature gate label.
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### Steps
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Include each step required to complete the feature. Typically this is a PR
implementing a feature, followed by a PR that stabilises the feature. However
for larger features an implementation could be broken up into multiple PRs.
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- [ ] Implementation (#131966)
- [ ] Adjust documentation ([see instructions on rustc-dev-guide][doc-guide])
- [ ] Formatting for new syntax has been added to the [Style Guide] ([nightly-style-procedure])
- [ ] Stabilization PR ([see instructions on rustc-dev-guide][stabilization-guide])

[stabilization-guide]: https://rustc-dev-guide.rust-lang.org/stabilization_guide.html#stabilization-pr
[doc-guide]: https://rustc-dev-guide.rust-lang.org/stabilization_guide.html#documentation-prs
[nightly-style-procedure]: https://github.com/rust-lang/style-team/blob/master/nightly-style-procedure.md 
[Style Guide]: https://github.com/rust-lang/rust/tree/master/src/doc/style-guide

### Unresolved Questions

### Implementation history

- #37973