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65de5d0472
rust/compiler/rustc_hir_analysis
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Matthias Krüger 65de5d0472
Rollup merge of #127871 - compiler-errors:recursive, r=estebank 
Mention that type parameters are used recursively on bivariance error

Right now when a type parameter is used recursively, even with indirection (so it has a finite size) we say that the type parameter is unused:

```
struct B<T>(Box<B<T>>);
```

This is confusing, because the type parameter is *used*, it just doesn't have its variance constrained. This PR tweaks that message to mention that it must be used *non-recursively*.

Not sure if we should actually mention "variance" here, but also I'd somewhat prefer we don't keep the power users in the dark w.r.t the real underlying issue, which is that the variance isn't constrained. That technical detail is reserved for a note, though.

cc `@fee1-dead`

Fixes #118976
Fixes #26283
Fixes #53191
Fixes #105740
Fixes #110466
2024-07-18 23:05:22 +02:00
..
src Rollup merge of #127871 - compiler-errors:recursive, r=estebank 2024-07-18 23:05:22 +02:00
Cargo.toml bump itertools to 0.12 2024-03-08 12:34:05 +03:00
messages.ftl Account for structs that have unused params in nested types in fields 2024-07-17 21:12:12 -04:00
README.md rustc_typeck to rustc_hir_analysis 2022-09-27 10:37:23 +02:00

README.md

For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.