Clarify `invalid_reference_casting` lint around interior mutable types
This is PR intends to clarify the `invalid_reference_casting` lint around interior mutable types by adding a note for them saying that they should go through `UnsafeCell::get`.
So for this code:
```rust
let cell = &std::cell::UnsafeCell::new(0);
let _num = &mut *(cell as *const _ as *mut i32);
```
the following note will be added to the lint output:
```diff
error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
--> $DIR/reference_casting.rs:68:16
|
LL | let _num = &mut *(cell as *const _ as *mut i32);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
+ = note: even for types with interior mutability, the only legal way to obtain a mutable pointer from a shared reference is through `UnsafeCell::get`
```
Suggestion are welcome around the note contents.
Fixes https://github.com/rust-lang/rust/issues/116410
cc `@RalfJung`
Bring back generic parameters for indices in rustc_abi and make it compile on stable
This effectively reverses https://github.com/rust-lang/rust/pull/107163, allowing rust-analyzer to depend on this crate again,
It also moves some glob imports / expands them in the first commit because they made it more difficult for me to reason about things.
Currently the test passes with the LLVM backend as the codegen unit
partitioning logic happens to place both the global_asm!() and the
function which calls the function defined by the global_asm!() in the
same CGU. With the Cranelift backend it breaks however as it will place
all assembly in separate codegen units to be passed to an external
linker.
The `rustc_span::FileName` enum already differentiates between real
files and "fake" files such as `<anon>`. We do not need to artificially
forbid real file names from ending in `>`.
Do not assert that hidden types don't have erased regions.
cc https://github.com/rust-lang/rust/issues/116306
`args` can have erased regions.
In the linked issue, this is reached by computing whether a large type is `Freeze` to compute its ABI.
I do not have a minimized test to include.
Add a note to duplicate diagnostics
Helps explain why there may be a difference between manual testing and the test suite output and highlights them as something to potentially look into
For existing duplicate diagnostics I just blessed them other than a few files that had other `NOTE` annotations in
docs: Correct terminology in std::cmp
This PR is the result of some discussions on URLO:
* [Traits in `std::cmp` and mathematical terminology](https://users.rust-lang.org/t/traits-in-std-cmp-and-mathematical-terminology/69887)
* [Are poker hands `Ord` or `PartialOrd`?](https://users.rust-lang.org/t/are-poker-hands-ord-or-partialord/82644)
Arguably, the documentation currently isn't very precise regarding mathematical terminology. This can lead to misunderstandings of what `PartialEq`, `Eq`, `PartialOrd`, and `Ord` actually do.
While I believe this PR doesn't give any new API guarantees, it expliclitly mentions that `PartialEq::eq(a, b)` may return `true` for two distinct values `a` and `b` (i.e. where `a` and `b` are not equal in the mathematical sense). This leads to the consequence that `Ord` may describe a weak ordering instead of a total ordering.
In either case, I believe this PR should be thoroughly reviewed, ideally by someone with mathematical background to make sure the terminology is correct now, and also to ensure that no unwanted new API guarantees are made.
In particular, the following problems are addressed:
* Some clarifications regarding used (mathematical) terminology:
* Avoid using the terms "total equality" and "partial equality" in favor of "equivalence relation" and "partial equivalence relation", which are well-defined and unambiguous.
* Clarify that `Ordering` is an ordering between two values (and not an order in the mathematical sense).
* Avoid saying that `PartialEq` and `Eq` are "equality comparisons" because the terminology "equality comparison" could be misleading: it's possible to implement `PartialEq` and `Eq` for other (partial) equivalence relations, in particular for relations where `a == b` for some `a` and `b` even when `a` and `b` are not the same value.
* Added a section "Strict and non-strict partial orders" to document that the `<=` and `>=` operators do not correspond to non-strict partial orders.
* Corrected section "Corollaries" in documenation of `Ord` in regard to `<` only describing a strict total order in cases where `==` conforms to mathematical equality.
* ~~Added a section "Weak orders" to explain that `Ord` may also describe a weak order or total preorder, depending on how `PartialEq::eq` has been implemented.~~ (Removed, see [comment](https://github.com/rust-lang/rust/pull/103046#issuecomment-1279929676))
* Made documentation easier to understand:
* Explicitly state at the beginning of `PartialEq`'s documentation comment that implementing the trait will provide the `==` and `!=` operators.
* Added an easier to understand rule when to implement `Eq` in addition to `PartialEq`: "if it’s guaranteed that `PartialEq::eq(a, a)` always returns `true`."
* Explicitly mention in documentation of `Eq` that the properties "symmetric" and "transitive" are already required by `PartialEq`.
