Retire the `unnamed_fields` feature for now
`#![feature(unnamed_fields)]` was implemented in part in #115131 and #115367, however work on that feature has (afaict) stalled and in the mean time there have been some concerns raised (e.g.[^1][^2]) about whether `unnamed_fields` is worthwhile to have in the language, especially in its current desugaring. Because it represents a compiler implementation burden including a new kind of anonymous ADT and additional complication to field selection, and is quite prone to bugs today, I'm choosing to remove the feature.
However, since I'm not one to really write a bunch of words, I'm specifically *not* going to de-RFC this feature. This PR essentially *rolls back* the state of this feature to "RFC accepted but not yet implemented"; however if anyone wants to formally unapprove the RFC from the t-lang side, then please be my guest. I'm just not totally willing to summarize the various language-facing reasons for why this feature is or is not worthwhile, since I'm coming from the compiler side mostly.
Fixes#117942Fixes#121161Fixes#121263Fixes#121299Fixes#121722Fixes#121799Fixes#126969Fixes#131041
Tracking:
* https://github.com/rust-lang/rust/issues/49804
[^1]: https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/Unnamed.20struct.2Funion.20fields
[^2]: https://github.com/rust-lang/rust/issues/49804#issuecomment-1972619108
Stabilize the `map`/`value` methods on `ControlFlow`
And fix the stability attribute on the `pub use` in `core::ops`.
libs-api in https://github.com/rust-lang/rust/issues/75744#issuecomment-2231214910 seemed reasonably happy with naming for these, so let's try for an FCP.
Summary:
```rust
impl<B, C> ControlFlow<B, C> {
pub fn break_value(self) -> Option<B>;
pub fn map_break<T>(self, f: impl FnOnce(B) -> T) -> ControlFlow<T, C>;
pub fn continue_value(self) -> Option<C>;
pub fn map_continue<T>(self, f: impl FnOnce(C) -> T) -> ControlFlow<B, T>;
}
```
Resolves#75744
``@rustbot`` label +needs-fcp +t-libs-api -t-libs
---
Aside, in case it keeps someone else from going down the same dead end: I looked at the `{break,continue}_value` methods and tried to make them `const` as part of this, but that's disallowed because of not having `const Drop`, so put it back to not even unstably-const.
Implement RFC3695 Allow boolean literals as cfg predicates
This PR implements https://github.com/rust-lang/rfcs/pull/3695: allow boolean literals as cfg predicates, i.e. `cfg(true)` and `cfg(false)`.
r? `@nnethercote` *(or anyone with parser knowledge)*
cc `@clubby789`
Refactoring to `OpaqueTyOrigin`
Pulled out of a larger PR that uses these changes to do cross-crate encoding of opaque origin, so we can use them for edition 2024 migrations. These changes should be self-explanatory on their own, tho 😄
Add `File` constructors that return files wrapped with a buffer
In addition to the light convenience, these are intended to raise visibility that buffering is something you should consider when opening a file, since unbuffered I/O is a common performance footgun to Rust newcomers.
ACP: https://github.com/rust-lang/libs-team/issues/446
Tracking Issue: #130804
linker: Allow MSVC to use import libraries following the Meson/MinGW convention
Hi all,
This PR implements support for `MsvcLinker` to use import libraries following Meson and the MinGW toolchain's naming convention. Meson [follows the `libfoo.dll.a` naming convention](https://mesonbuild.com/FAQ.html#why-does-building-my-project-with-msvc-output-static-libraries-called-libfooa) to disambiguate between static and import libraries.
This support already existed for static libraries (see #100101), but not for dynamic libraries. The latter case was added by duplicating the logic in `native_libs::find_native_static_library`, but a separate case was added in `link_dylib_by_name` for the Windows CRT libraries which must be handled by the linker itself.
See for prerequisites #129366, #126094, and #128370.
All feedback is appreciated!
Fixes#122455
cc `@sdroege` `@nirbheek`
Correctly handle stability of `#[diagnostic]` attributes
This commit changes the way we treat the stability of attributes in the
`#[diagnostic]` namespace. Instead of relaying on ad-hoc checks to
ensure at call side that a certain attribute is really usable at that
location it centralises the logic to one place. For diagnostic
attributes comming from other crates it just skips serializing
attributes that are not stable and that do not have the corresponding
feature enabled. For attributes from the current crate we can just use
the feature information provided by `TyCtx`.
r? `@compiler-errors`
This commit changes the way we treat the stability of attributes in the
`#[diagnostic]` namespace. Instead of relaying on ad-hoc checks to
ensure at call side that a certain attribute is really usable at that
location it centralises the logic to one place. For diagnostic
attributes comming from other crates it just skips serializing
attributes that are not stable and that do not have the corresponding
feature enabled. For attributes from the current crate we can just use
the feature information provided by `TyCtx`.
Make decoding non-optional `LazyArray` panic if not set
Tables may be [defined](9649706ead/compiler/rustc_metadata/src/rmeta/mod.rs (L377)) as `optional:` or `defaulted:`. If optional, if we try to read a value from a key that was never encoded, we should panic. This has high value in ensuring correctness over a defaulted table, so the tradeoff is worth considering, since it signals the compiler has a buggy encode impl, rather than just defaulting to a value.
HOWEVER, `optional:` arrays were side-stepping this. So this PR fixes that, and makes `optional:` tables of `LazyArray` act like `LazyValue`, and panic if it's not assigned a value during encoding.
During this PR, I found that `deduced_param_attrs` has buggy (?? i think??) implementation where it will refuse to encode cross-crate `deduced_param_attrs` unless we're codegening, we're optimizing the library, and incremental is disabled. This seems incredibly wrong, but I don't want to fix it in this PR.
9649706ead/compiler/rustc_metadata/src/rmeta/encoder.rs (L1733-L1747)
Stop using `ty::GenericPredicates` for non-predicates_of queries
`GenericPredicates` is a struct of several parts: A list of of an item's own predicates, and a parent def id (and some effects related stuff, but ignore that since it's kinda irrelevant). When instantiating these generic predicates, it calls `predicates_of` on the parent and instantiates its predicates, and appends the item's own instantiated predicates too:
acb4e8b625/compiler/rustc_middle/src/ty/generics.rs (L407-L413)
Notice how this should result in a recursive set of calls to `predicates_of`... However, `GenericPredicates` is *also* misused by a bunch of *other* queries as a convenient way of passing around a list of predicates. For these queries, we don't ever set the parent def id of the `GenericPredicates`, but if we did, then this would be very easy to mistakenly call `predicates_of` instead of some other intended parent query.
Given that footgun, and the fact that we don't ever even *use* the parent def id in the `GenericPredicates` returned from queries like `explicit_super_predicates_of`, It really has no benefit over just returning `&'tcx [(Clause<'tcx>, Span)]`.
This PR additionally opts to wrap the results of `EarlyBinder`, as we've tended to use that in the return type of these kinds of queries to properly convey that the user has params to deal with, and it also gives a convenient way of iterating over a slice of things after instantiating.
Simplify some extern providers
Simplifies some extern crate providers:
1. Generalize the `ProcessQueryValue` identity impl to work on non-`Option` types.
2. Allow `ProcessQueryValue` to wrap its output in an `EarlyBinder`, to simplify `explicit_item_bounds`/`explicit_item_super_predicates`.
3. Use `{ table }` and friends more when possible.
linker: Synchronize native library search in rustc and linker
Also search for static libraries with alternative naming (`libname.a`) on MSVC when producing executables or dynamic libraries, and not just rlibs.
This unblocks https://github.com/rust-lang/rust/pull/123436.
try-job: x86_64-msvc
Move `'tcx` lifetime off of impl and onto methods for `CrateMetadataRef`
Unconstrained type and const variables are not allowed, but unconstrained lifetimes are. This is not very good style, though, and it leads to unnecessary captures of a lifetime in edition 2024 (not that it matters, but it does trigger the edition migration lint).
