The reverse conversion unfortunately causes unexpected errors like:
```
error[E0277]: the trait bound `!: std::convert::From<()>` is not satisfied
--> src/librustc_metadata/encoder.rs:105:9
|
105 | self.emit_usize(seq.len)?;
| ^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::convert::From<()>` is not implemented for `!`
|
= help: the following implementations were found:
<! as std::convert::From<std::convert::Infallible>>
= note: the trait is implemented for `()`. Possibly this error has been caused by changes to Rust's type-inference algorithm (see: https://github.com/rust-lang/rust/issues/48950 for more info). Consider whether you meant to use the type `()` here instead.
= note: required by `std::convert::From::from`
```
I don’t understand why this error happens.
If I’m reading the code correctly the return types of `emit_usize`
and of the method that contains line 105 are both `Result<(), !>`,
so the expansion of the `?` operator should involve `!: From<!>`,
not `From<()>`.
Is this a type inference bug?
target/uefi: clarify documentation
This clarifies why FP-units are disabled on UEFI targets, as well as
why we must opt into the NXCOMPAT feature.
I did find some time to investigate why GRUB and friends disable FP on
UEFI. The specification explicitly allows using MMX/SSE/AVX, but as it
turns out it does not mandate enabling the instruction sets explicitly.
Hence, any use of these instructions will trigger CPU exceptions,
unless an application explicitly enables them (which is not an option,
as these are global flags that better be controlled by the
kernel/firmware).
Furthermore, UEFI systems are allowed to mark any non-code page as
non-executable. Hence, we must make sure to never place code on the
stack or heap. So we better pass /NXCOMPAT to the linker for it to
complain if it ever places code in non-code pages.
Lastly, this fixes some typos in related comments.
r? @alexcrichton
Only suggest imports if not imported.
Fixes#42944 and fixes#53430.
This commit modifies name resolution error reporting so that if a name
is in scope and has been imported then we do not suggest importing it.
This can occur when we add a label about constructors not being visible
due to private fields. In these cases, we know that the struct/variant
has been imported and we should silence any suggestions to import the
struct/variant.
r? @estebank
Fix ICE and invalid filenames in MIR printing code
* Don't panic when printing MIR for associated constants
* Don't use `<` and `>` in filenames, since they aren't allowed on Windows.
r? @eddyb
cc @RalfJung
Improve the error messages for missing stability attributes
This makes the capitalisation consistent and provides more context (especially for missing top-level attributes).
Ignore future deprecations in #[deprecated]
The future deprecation warnings should only apply to `#[rustc_deprecated]` as they take into account rustc's version. Fixes#57952.
I've also slightly modified rustdoc's display of future deprecation notices to make it more consistent, so I'm assigning a rustdoc team member for review to make sure this is okay.
r? @GuillaumeGomez
This clarifies why FP-units are disabled on UEFI targets, as well as
why we must opt into the NXCOMPAT feature.
I did find some time to investigate why GRUB and friends disable FP on
UEFI. The specification explicitly allows using MMX/SSE/AVX, but as it
turns out it does not mandate enabling the instruction sets explicitly.
Hence, any use of these instructions will trigger CPU exceptions,
unless an application explicitly enables them (which is not an option,
as these are global flags that better be controlled by the
kernel/firmware).
Furthermore, UEFI systems are allowed to mark any non-code page as
non-executable. Hence, we must make sure to never place code on the
stack or heap. So we better pass /NXCOMPAT to the linker for it to
complain if it ever places code in non-code pages.
Lastly, this fixes some typos in related comments.
Fixes rustdoc in stage 0, stage 1
When a request for rustdoc is passed for stage 0, x.py build --stage 0
src/tools/rustdoc or ensure(tool::Rustdoc { .. }) with top_stage = 0, we
return the rustdoc for that compiler (i.e., the beta rustdoc).
This fixes stage 0 of https://github.com/rust-lang/rust/issues/52186 as well as being part of general workflow improvements (making stage 0 testing for std work) for rustbuild.
The stage 1 fix (second commit) completely resolves the problem, so this fixes https://github.com/rust-lang/rust/issues/52186.
SGX target: simplify usercall internals
This moves logic from assembly to Rust and removes the special case for exit/panic handling, merging it with regular usercall handling.
Also, this fixes a bug in the exit usercall introduced in a75ae00. The bug would make regular exits look like panics with high probability. It would also with some probability leak information through uncleared registers.
cc @VardhanThigle
r? @alexcrichton
