Reflection MVP
I am opening this PR for discussion about the general design we should start out with, as there are various options (that are not too hard to transition between each other, so we should totally just pick one and go with it and reiterate later)
r? @scottmcm and @joshtriplett
project goal issue: https://github.com/rust-lang/rust-project-goals/issues/406
tracking issue: https://github.com/rust-lang/rust/issues/146922
The design currently implemented by this PR is
* `TypeId::info` (method, usually used as `id.info()` returns a `Type` struct
* the `Type` struct has fields that contain information about the type
* the most notable field is `kind`, which is a non-exhaustive enum over all possible type kinds and their specific information. So it has a `Tuple(Tuple)` variant, where the only field is a `Tuple` struct type that contains more information (The list of type ids that make up the tuple).
* To get nested type information (like the type of fields) you need to call `TypeId::info` again.
* There is only one language intrinsic to go from `TypeId` to `Type`, and it does all the work
An alternative design could be
* Lots of small methods (each backed by an intrinsic) on `TypeId` that return all the individual information pieces (size, align, number of fields, number of variants, ...)
* This is how C++ does it (see https://lemire.me/blog/2025/06/22/c26-will-include-compile-time-reflection-why-should-you-care/ and https://isocpp.org/files/papers/P2996R13.html#member-queries)
* Advantage: you only get the information you ask for, so it's probably cheaper if you get just one piece of information for lots of types (e.g. reimplementing size_of in terms of `TypeId::info` is likely expensive and wasteful)
* Disadvantage: lots of method calling (and `Option` return types, or "general" methods like `num_fields` returning 0 for primitives) instead of matching and field accesses
* a crates.io crate could implement `TypeId::info` in terms of this design
The backing implementation is modular enough that switching from one to the other is probably not an issue, and the alternative design could be easier for the CTFE engine's implementation, just not as nice to use for end users (without crates wrapping the logic)
One wart of this design that I'm fixing in separate branches is that `TypeId::info` will panic if used at runtime, while it should be uncallable
resolve: Factor out and document the glob binding overwriting logic
Also, avoid creating fresh name declarations and overwriting declarations in modules to update some fields in `DeclData`, when possible.
Instead, change the fields directly in `DeclData` using cells.
Unblocks https://github.com/rust-lang/rust/pull/149195.
Don't check `[mentions]` paths in submodules from tidy
As we were reminded in [#triagebot > Mentions glob matching](https://rust-lang.zulipchat.com/#narrow/channel/224082-triagebot/topic/Mentions.20glob.20matching/with/567093226), triagebot cannot see changes in submodules.
So let's reflect that in the `tidy` check to avoid accidentally adding paths inside submodules.
I tested it with these entries:
```toml
[mentions."src/tools/cargo"]
cc = ["@ehuss"]
[mentions."src/tools/cargo/"]
cc = ["@ehuss"]
[mentions."src/tools/cargo/*"]
cc = ["@ehuss"]
[mentions."src/tools/cargo/README.md"]
cc = ["@ehuss"]
```
and got (as expected):
```
tidy [triagebot]: triagebot.toml [mentions.*] 'src/tools/cargo/README.md' cannot match inside a submodule
tidy [triagebot]: triagebot.toml [mentions.*] contains 'src/tools/cargo/*' which doesn't match any file or directory in the repository
```
Fix std::fs::copy on WASI by setting proper OpenOptions flags
When PR rust-lang/rust#147572 switched WASI to use Unix-style filesystem APIs, the open_to_and_set_permissions function for WASI was implemented to call OpenOptions::new().open() without setting any access mode flags.
This causes std::fs::copy to fail with the error:
"must specify at least one of read, write, or append access"
The fix is to explicitly set .write(true), .create(true), and .truncate(true) on the OpenOptions, matching the behavior of the non-WASI Unix implementation but without the permission handling that WASI doesn't support.
Minimal reproduction:
```rs
fn main() {
std::fs::write("/src.txt", b"test").unwrap();
match std::fs::copy("/src.txt", "/dst.txt") {
Ok(_) => println!("PASS: fs::copy works!"),
Err(e) => println!("FAIL: {}", e),
}
}
```
# Compile and run:
rustc +nightly --target wasm32-wasip2 test.rs -o test.wasm
wasmtime -S cli --dir . test.wasm
# Before fix: FAIL: must specify at least one of read, write, or append access
# After fix: PASS: fs::copy works!
Note: The existing test library/std/src/fs/tests.rs::copy_file_ok would have caught this regression if the std test suite ran on WASI targets. Currently std tests don't compile for wasm32-wasip2 due to Unix-specific test code in library/std/src/sys/fd/unix/tests.rs.
Fixes the regression introduced in nightly-2025-12-10.
r? @alexcrichton
Fix for ICE: eii: fn / macro rules None in find_attr()
Closesrust-lang/rust#149981
This used to ICE:
```rust
macro_rules! foo_impl {}
#[eii]
fn foo_impl() {}
```
`#[eii]` generates a macro (called `foo_impl`) and a default impl. So the partial expansion used to roughly look like the following:
```rust
macro_rules! foo_impl {} // actually resolves here
extern "Rust" {
fn foo_impl();
}
#[eii_extern_target(foo_impl)]
macro foo_impl {
() => {};
}
const _: () = {
#[implements_eii(foo_impl)] // assumed to name resolve to the macro v2 above
fn foo_impl() {}
};
```
Now, shadowing rules for macrov2 and macrov1 are super weird! Take a look at this: https://play.rust-lang.org/?version=nightly&mode=debug&edition=2024&gist=23f21421921360478b0ec0276711ad36
So instead of resolving to the macrov2, we resolve the macrov1 named the same thing.
A regression test was added to this, and some span_delayed_bugs were added to make sure we catch this in the right places. But that didn't fix the root cause.
To make sure this simply cannot happen again, I made it so that we don't even need to do a name resolution for the default. In other words, the new partial expansion looks more like:
```rust
macro_rules! foo_impl {}
extern "Rust" {
fn foo_impl(); // resolves to here now!!!
}
#[eii_extern_target(foo_impl)]
macro foo_impl {
() => {};
}
const _: () = {
#[implements_eii(known_extern_target=foo_impl)] // still name resolved, but directly to the foreign function.
fn foo_impl() {}
};
```
The reason this helps is that name resolution for non-macros is much more predictable. It's not possible to have two functions like that with the same name in scope.
We used to key externally implementable items off of the defid of the macro, but now the unique identifier is the foreign function's defid which seems much more sane.
Finally, I lied a tiny bit because the above partial expansion doesn't actually work.
```rust
extern "Rust" {
fn foo_impl(); // not to here
}
const _: () = {
#[implements_eii(known_extern_target=foo_impl)] // actually resolves to this function itself
fn foo_impl() {} // <--- so to here
};
```
So the last few commits change the expansion to actually be this:
```rust
macro_rules! foo_impl {}
extern "Rust" {
fn foo_impl(); // resolves to here now!!!
}
#[eii_extern_target(foo_impl)]
macro foo_impl {
() => {};
}
const _: () = {
mod dflt { // necessary, otherwise `super` doesn't work
use super::*;
#[implements_eii(known_extern_target=super::foo_impl)] // now resolves to outside the `dflt` module, so the foreign item.
fn foo_impl() {}
}
};
```
I apologize to whoever needs to review this, this is very subtle and I hope this makes it clear enough 😭.
Fix ICE in inline always warning emission.
The calls to `def_path_str` were outside the decorate callback in `node_span_lint` which caused an ICE when the warning was an allowed warning due to the call to `def_path_str` being executed but the warning not actually being emitted.
r? @davidtwco
Update cargo submodule
27 commits in 94c368ad2b9db0f0da5bdd8421cea13786ce4412..8c133afcd5e0d69932fe11f5907683723f8d361d
2025-12-26 19:39:15 +0000 to 2026-01-09 03:50:15 +0000
- Isolate build script metadata progation between std and non-std crates (rust-lang/cargo#16489)
- Add Clippy like lint groups (rust-lang/cargo#16464)
- feat: in-memory only `Manifest` (rust-lang/cargo#16409)
- Fixed incorrect version comparision during build script dependency selection (rust-lang/cargo#16486)
- refactor: new type for unit index (rust-lang/cargo#16485)
- feat(test): Make CARGO_BIN_EXE_ available at runtime (rust-lang/cargo#16421)
- fix(package): detect dirty files when run from workspace member (rust-lang/cargo#16479)
- fix(timing)!: remove `--timings=<FMT>` optional format values (rust-lang/cargo#16420)
- docs(unstable): expand docs for `-Zbuild-analysis` (rust-lang/cargo#16476)
- test: add `-Zunstable-options` with custom targets (rust-lang/cargo#16467)
- feat(report): add cargo report rebuilds (rust-lang/cargo#16456)
- feat(test-support): Use test name for dir when running tests (rust-lang/cargo#16121)
- refactor: Migrate some cases to expect/reason (rust-lang/cargo#16461)
- docs(build-script): clarify OUT_DIR is not cleaned between builds (rust-lang/cargo#16437)
- chore: Update dependencies (rust-lang/cargo#16460)
- Update handlebars to 6.4.0 (rust-lang/cargo#16457)
- chore(deps): update alpine docker tag to v3.23 (rust-lang/cargo#16454)
- Any build scripts can now use cargo::metadata=KEY=VALUE (rust-lang/cargo#16436)
- fix(log): add `dependencies` field to `UnitRegistered` (rust-lang/cargo#16448)
- Implement fine grain locking for `build-dir` (rust-lang/cargo#16155)
- feat(resolver): List features when no close match (rust-lang/cargo#16445)
- feat(report): new command `cargo report sessions` (rust-lang/cargo#16428)
- feat (patch): Display where the patch was defined in patch-related error messages (rust-lang/cargo#16407)
- test(build-rs): Reduce from 'build' to 'check' where possible (rust-lang/cargo#16444)
- feat(toml): TOML 1.1 parse support (rust-lang/cargo#16415)
- feat(report): support --manifest-path in `cargo report timings` (rust-lang/cargo#16441)
- fix(vendor): recursively filter git files in subdirectories (rust-lang/cargo#16439)
When PR #147572 switched WASI to use Unix-style filesystem APIs, the
open_to_and_set_permissions function for WASI was implemented to call
OpenOptions::new().open() without setting any access mode flags.
This causes std::fs::copy to fail with the error:
"must specify at least one of read, write, or append access"
The fix is to explicitly set .write(true), .create(true), and
.truncate(true) on the OpenOptions, matching the behavior of the
non-WASI Unix implementation but without the permission handling
that WASI doesn't support.
Minimal reproduction:
fn main() {
std::fs::write("/src.txt", b"test").unwrap();
match std::fs::copy("/src.txt", "/dst.txt") {
Ok(_) => println!("PASS: fs::copy works!"),
Err(e) => println!("FAIL: {}", e),
}
}
# Compile and run:
rustc +nightly --target wasm32-wasip2 test.rs -o test.wasm
wasmtime -S cli --dir . test.wasm
# Before fix: FAIL: must specify at least one of read, write, or append access
# After fix: PASS: fs::copy works!
Note: The existing test library/std/src/fs/tests.rs::copy_file_ok
would have caught this regression if the std test suite ran on WASI
targets. Currently std tests don't compile for wasm32-wasip2 due to
Unix-specific test code in library/std/src/sys/fd/unix/tests.rs.
Fixes the regression introduced in nightly-2025-12-10.
Rollup of 11 pull requests
Successful merges:
- rust-lang/rust#150272 (docs(core): update `find()` and `rfind()` examples)
- rust-lang/rust#150385 (fix `Expr::can_have_side_effects` for `[x; N]` style array literal and binary expressions)
- rust-lang/rust#150561 (Finish transition from `semitransparent` to `semiopaque` for `rustc_macro_transparency`)
- rust-lang/rust#150574 (Clarify `MoveData::init_loc_map`.)
- rust-lang/rust#150762 (Use functions more in rustdoc GUI tests)
- rust-lang/rust#150808 (rename the `derive_{eq, clone_copy}` features to `*_internals`)
- rust-lang/rust#150816 (Fix trait method anchor disappearing before user can click on it)
- rust-lang/rust#150821 (tests/ui/borrowck/issue-92157.rs: Remove (bug not fixed))
- rust-lang/rust#150829 (make attrs actually use `Target::GenericParam`)
- rust-lang/rust#150834 (Add tracking issue for `feature(multiple_supertrait_upcastable)`)
- rust-lang/rust#150864 (The aarch64-unknown-none target requires NEON, so the docs were wrong.)
r? @ghost
Add tracking issue for `feature(multiple_supertrait_upcastable)`
Move feature(multiple_supertrait_upcastable) to the actual feature gates section (from the internal feature gates section) and give it a tracking issue.
Tracking issue: rust-lang/rust#150833
Fixes https://github.com/rust-lang/rust/issues/150773
This feature is for the `multiple_supertrait_upcastable` lint, which was added as `unstable` without a tracking issue, but was placed in the internal feature gates section. This PR moves its listing to the actual feature gates section and gives it a tracking issue.
If the lint is intended to stay internal-only, then this can be changed to instead mark it as `internal` (and maybe close the tracking issue).
make attrs actually use `Target::GenericParam`
currently attributes lower `GenericParam` -> `Target::Param` this PR fixes this, so that `GenericParam` is lowered to `Target::GenericParam`
r? @JonathanBrouwer
tests/ui/borrowck/issue-92157.rs: Remove (bug not fixed)
The bug the test tests for is masked by the wrong `#[lang = "start"]` signature. If the signature is corrected, the test builds. But that is not because the bug is fixed, but because the test has been changed too much from the original reproducer. The original reproducer still ICE:s. See https://github.com/rust-lang/rust/issues/92157#issuecomment-3722060317.
But that's fine since in the latest compiler says:
> note: using internal features is not supported and expected to cause internal compiler errors when used incorrectly
So let's remove the test and close the issue as "won't fix". See https://github.com/rust-lang/rust/issues/92157#issuecomment-3725036997.
r? @JohnTitor since you added the test in https://github.com/rust-lang/rust/pull/106878
Fix trait method anchor disappearing before user can click on it
A good example of this bug is going to https://doc.rust-lang.org/nightly/nightly-rustc/rustc_hir_analysis/collect/struct.ItemCtxt.html#impl-HirTyLowerer%3C'tcx%3E-for-ItemCtxt%3C'tcx%3E, and then try to click on the `§` anchor of the `tcx` method.
The solution to this bug is to simply "glue" the anchor to the method, so when the mouse cursor moves to it, there is no gap between the two, preventing the anchor to disappear (hopefully this explanation doesn't make sense only to me ^^').
First commit fixes the bug by expanding the anchor size.
Second commit is a small clean-up of the GUI test.
Third commit actually adds the GUI regression test.
cc @BoxyUwU
r? @camelid
rename the `derive_{eq, clone_copy}` features to `*_internals`
Features like `derive_from` and `derive_coerce_pointee` refer to actual unstable derive macros, but the `derive_eq` and `derive_clone_copy` features are internal hacks. Rename them accordingly by adding the suffix `_internals`.
Use functions more in rustdoc GUI tests
Now that conditions are supported in `browser-ui-test`, we can start simplify some parts of the tests. This is a first cleanup, but I guess a lot more could be simplified. For follow-ups I guess. :)
I made some improvements in backtrace display in `browser-ui-test`, hence the version update once more.
r? @lolbinarycat
Clarify `MoveData::init_loc_map`.
Change the `SmallVec` size from 4 to 1, because that's sufficient in the vast majority of cases. (This doesn't affect performance in practice, so it's more of a code clarity change than a performance change.)
r? @cjgillot
Finish transition from `semitransparent` to `semiopaque` for `rustc_macro_transparency`
Since it's a bit annoying to have different names for the same thing.
My understanding is that this is just internal stuff that is not part of any public API even tough rust-analyzer knows about it.
Continuation of
- https://github.com/rust-lang/rust/pull/139084.
Discovered while investigating
- https://github.com/rust-lang/rust/issues/150514
fix `Expr::can_have_side_effects` for `[x; N]` style array literal and binary expressions
AFAIK `[0; 3]` is basically a syntax sugar for `[0, 0, 0]` so it should return whether the repeat's element can have side effects, like what it does on arrays.
And it seems that the rule for unary operators and indexings can be applied to binary operators as well.
Stop emitting UbChecks on every Vec→Slice
Spotted this in rust-lang/rust#148766's test changes. It doesn't seem like this ubcheck would catch anything useful; let's see if skipping it helps perf. (After all, this is inside *every* `[]` on a vec, among other things.)
