Initial implementation of `#[feature(default_field_values]`, proposed in https://github.com/rust-lang/rfcs/pull/3681.
Support default fields in enum struct variant
Allow default values in an enum struct variant definition:
```rust
pub enum Bar {
Foo {
bar: S = S,
baz: i32 = 42 + 3,
}
}
```
Allow using `..` without a base on an enum struct variant
```rust
Bar::Foo { .. }
```
`#[derive(Default)]` doesn't account for these as it is still gating `#[default]` only being allowed on unit variants.
Support `#[derive(Default)]` on enum struct variants with all defaulted fields
```rust
pub enum Bar {
#[default]
Foo {
bar: S = S,
baz: i32 = 42 + 3,
}
}
```
Check for missing fields in typeck instead of mir_build.
Expand test with `const` param case (needs `generic_const_exprs` enabled).
Properly instantiate MIR const
The following works:
```rust
struct S<A> {
a: Vec<A> = Vec::new(),
}
S::<i32> { .. }
```
Add lint for default fields that will always fail const-eval
We *allow* this to happen for API writers that might want to rely on users'
getting a compile error when using the default field, different to the error
that they would get when the field isn't default. We could change this to
*always* error instead of being a lint, if we wanted.
This will *not* catch errors for partially evaluated consts, like when the
expression relies on a const parameter.
Suggestions when encountering `Foo { .. }` without `#[feature(default_field_values)]`:
- Suggest adding a base expression if there are missing fields.
- Suggest enabling the feature if all the missing fields have optional values.
- Suggest removing `..` if there are no missing fields.
Refactor `where` predicates, and reserve for attributes support
Refactor `WherePredicate` to `WherePredicateKind`, and reserve for attributes support in `where` predicates.
This is a part of #115590 and is split from #132388.
r? petrochenkov
When labels are present, the `noreturn` option really means that asm block
won't fallthrough -- if labels are present, then outputs can still be
meaningfully used.
Unify FnKind between AST visitors and make WalkItemKind more straight forward
Unifying `FnKind` requires a bunch of changes to `WalkItemKind::walk` signature so I'll change them in one go
related to #128974
r? `@petrochenkov`
Important: we know from the `parse_annotatable_with` call above the call
site that only some of the `Annotatable` variants are possible. The
remaining cases can be replaced with `unreachable!`.
They each have a single callsite, and the result is always unwrapped, so
the `Option<Annotatable>` return type is misleading.
Also, the comment at the `configure_annotatable` call site is wrong,
talking about a result vector, so this commit also removes that.
Rename macro `SmartPointer` to `CoercePointee`
As per resolution #129104 we will rename the macro to better reflect the technical specification of the feature and clarify the communication.
- `SmartPointer` is renamed to `CoerceReferent`
- `#[pointee]` attribute is renamed to `#[referent]`
- `#![feature(derive_smart_pointer)]` gate is renamed to `#![feature(derive_coerce_referent)]`.
- Any mention of `SmartPointer` in the file names are renamed accordingly.
r? `@compiler-errors`
cc `@nikomatsakis` `@Darksonn`
Const stability checks v2
The const stability system has served us well ever since `const fn` were first stabilized. It's main feature is that it enforces *recursive* validity -- a stable const fn cannot internally make use of unstable const features without an explicit marker in the form of `#[rustc_allow_const_fn_unstable]`. This is done to make sure that we don't accidentally expose unstable const features on stable in a way that would be hard to take back. As part of this, it is enforced that a `#[rustc_const_stable]` can only call `#[rustc_const_stable]` functions. However, some problems have been coming up with increased usage:
- It is baffling that we have to mark private or even unstable functions as `#[rustc_const_stable]` when they are used as helpers in regular stable `const fn`, and often people will rather add `#[rustc_allow_const_fn_unstable]` instead which was not our intention.
- The system has several gaping holes: a private `const fn` without stability attributes whose inherited stability (walking up parent modules) is `#[stable]` is allowed to call *arbitrary* unstable const operations, but can itself be called from stable `const fn`. Similarly, `#[allow_internal_unstable]` on a macro completely bypasses the recursive nature of the check.
Fundamentally, the problem is that we have *three* disjoint categories of functions, and not enough attributes to distinguish them:
1. const-stable functions
2. private/unstable functions that are meant to be callable from const-stable functions
3. functions that can make use of unstable const features
Functions in the first two categories cannot use unstable const features and they can only call functions from the first two categories.
This PR implements the following system:
- `#[rustc_const_stable]` puts functions in the first category. It may only be applied to `#[stable]` functions.
- `#[rustc_const_unstable]` by default puts functions in the third category. The new attribute `#[rustc_const_stable_indirect]` can be added to such a function to move it into the second category.
- `const fn` without a const stability marker are in the second category if they are still unstable. They automatically inherit the feature gate for regular calls, it can now also be used for const-calls.
Also, all the holes mentioned above have been closed. There's still one potential hole that is hard to avoid, which is when MIR building automatically inserts calls to a particular function in stable functions -- which happens in the panic machinery. Those need to be manually marked `#[rustc_const_stable_indirect]` to be sure they follow recursive const stability. But that's a fairly rare and special case so IMO it's fine.
The net effect of this is that a `#[unstable]` or unmarked function can be constified simply by marking it as `const fn`, and it will then be const-callable from stable `const fn` and subject to recursive const stability requirements. If it is publicly reachable (which implies it cannot be unmarked), it will be const-unstable under the same feature gate. Only if the function ever becomes `#[stable]` does it need a `#[rustc_const_unstable]` or `#[rustc_const_stable]` marker to decide if this should also imply const-stability.
Adding `#[rustc_const_unstable]` is only needed for (a) functions that need to use unstable const lang features (including intrinsics), or (b) `#[stable]` functions that are not yet intended to be const-stable. Adding `#[rustc_const_stable]` is only needed for functions that are actually meant to be directly callable from stable const code. `#[rustc_const_stable_indirect]` is used to mark intrinsics as const-callable and for `#[rustc_const_unstable]` functions that are actually called from other, exposed-on-stable `const fn`. No other attributes are required.
Also see the updated dev-guide at https://github.com/rust-lang/rustc-dev-guide/pull/2098.
I think in the future we may want to tweak this further, so that in the hopefully common case where a public function's const-stability just exactly mirrors its regular stability, we never have to add any attribute. But right now, once the function is stable this requires `#[rustc_const_stable]`.
### Open question
There is one point I could see we might want to do differently, and that is putting `#[rustc_const_unstable]` functions (but not intrinsics) in category 2 by default, and requiring an extra attribute for `#[rustc_const_not_exposed_on_stable]` or so. This would require a bunch of extra annotations, but would have the advantage that turning a `#[rustc_const_unstable]` into `#[rustc_const_stable]` will never change the way the function is const-checked. Currently, we often discover in the const stabilization PR that a function needs some other unstable const things, and then we rush to quickly deal with that. In this alternative universe, we'd work towards getting rid of the `rustc_const_not_exposed_on_stable` before stabilization, and once that is done stabilization becomes a trivial matter. `#[rustc_const_stable_indirect]` would then only be used for intrinsics.
I think I like this idea, but might want to do it in a follow-up PR, as it will need a whole bunch of annotations in the standard library. Also, we probably want to convert all const intrinsics to the "new" form (`#[rustc_intrinsic]` instead of an `extern` block) before doing this to avoid having to deal with two different ways of declaring intrinsics.
Cc `@rust-lang/wg-const-eval` `@rust-lang/libs-api`
Part of https://github.com/rust-lang/rust/issues/129815 (but not finished since this is not yet sufficient to safely let us expose `const fn` from hashbrown)
Fixes https://github.com/rust-lang/rust/issues/131073 by making it so that const-stable functions are always stable
try-job: test-various
Rollup of 9 pull requests
Successful merges:
- #122670 (Fix bug where `option_env!` would return `None` when env var is present but not valid Unicode)
- #131095 (Use environment variables instead of command line arguments for merged doctests)
- #131339 (Expand set_ptr_value / with_metadata_of docs)
- #131652 (Move polarity into `PolyTraitRef` rather than storing it on the side)
- #131675 (Update lint message for ABI not supported)
- #131681 (Fix up-to-date checking for run-make tests)
- #131702 (Suppress import errors for traits that couldve applied for method lookup error)
- #131703 (Resolved python deprecation warning in publish_toolstate.py)
- #131710 (Remove `'apostrophes'` from `rustc_parse_format`)
r? `@ghost`
`@rustbot` modify labels: rollup
Move polarity into `PolyTraitRef` rather than storing it on the side
Arguably we could move these modifiers into `TraitRef` instead of `PolyTraitRef`, but I see `TraitRef` as simply the *path* part of the trait ref. It doesn't really matter -- refactoring this further is much easier now.
Fix bug where `option_env!` would return `None` when env var is present but not valid Unicode
Fixes#122669 by making `option_env!` emit an error when the value of the environment variable is not valid Unicode.
Autodiff Upstreaming - enzyme frontend
This is an upstream PR for the `autodiff` rustc_builtin_macro that is part of the autodiff feature.
For the full implementation, see: https://github.com/rust-lang/rust/pull/129175
**Content:**
It contains a new `#[autodiff(<args>)]` rustc_builtin_macro, as well as a `#[rustc_autodiff]` builtin attribute.
The autodiff macro is applied on function `f` and will expand to a second function `df` (name given by user).
It will add a dummy body to `df` to make sure it type-checks. The body will later be replaced by enzyme on llvm-ir level,
we therefore don't really care about the content. Most of the changes (700 from 1.2k) are in `compiler/rustc_builtin_macros/src/autodiff.rs`, which expand the macro. Nothing except expansion is implemented for now.
I have a fallback implementation for relevant functions in case that rustc should be build without autodiff support. The default for now will be off, although we want to flip it later (once everything landed) to on for nightly. For the sake of CI, I have flipped the defaults, I'll revert this before merging.
**Dummy function Body:**
The first line is an `inline_asm` nop to make inlining less likely (I have additional checks to prevent this in the middle end of rustc. If `f` gets inlined too early, we can't pass it to enzyme and thus can't differentiate it.
If `df` gets inlined too early, the call site will just compute this dummy code instead of the derivatives, a correctness issue. The following black_box lines make sure that none of the input arguments is getting optimized away before we replace the body.
**Motivation:**
The user facing autodiff macro can verify the user input. Then I write it as args to the rustc_attribute, so from here on I can know that these values should be sensible. A rustc_attribute also turned out to be quite nice to attach this information to the corresponding function and carry it till the backend.
This is also just an experiment, I expect to adjust the user facing autodiff macro based on user feedback, to improve usability.
As a simple example of what this will do, we can see this expansion:
From:
```
#[autodiff(df, Reverse, Duplicated, Const, Active)]
pub fn f1(x: &[f64], y: f64) -> f64 {
unimplemented!()
}
```
to
```
#[rustc_autodiff]
#[inline(never)]
pub fn f1(x: &[f64], y: f64) -> f64 {
::core::panicking::panic("not implemented")
}
#[rustc_autodiff(Reverse, Duplicated, Const, Active,)]
#[inline(never)]
pub fn df(x: &[f64], dx: &mut [f64], y: f64, dret: f64) -> f64 {
unsafe { asm!("NOP"); };
::core::hint::black_box(f1(x, y));
::core::hint::black_box((dx, dret));
::core::hint::black_box(f1(x, y))
}
```
I will add a few more tests once I figured out why rustc rebuilds every time I touch a test.
Tracking:
- https://github.com/rust-lang/rust/issues/124509
try-job: dist-x86_64-msvc
Special treatment empty tuple when suggest adding a string literal in format macro.
For example:
```rust
let s = "123";
println!({}, "sss", s);
```
Suggest:
`println!("{:?} {} {}", {}, "sss", s);`
fixes#130170
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
Don't allow the `#[pointee]` attribute where it doesn't belong
Error if the `#[pointee]` attribute is applied to anything but generic type parameters.
Closes#128485
Related to #123430
- fix for divergence
- fix error message
- fix another cranelift test
- fix some cranelift things
- don't set the NORETURN option for naked asm
- fix use of naked_asm! in doc comment
- fix use of naked_asm! in run-make test
- use `span_bug` in unreachable branch
Fix error span if arg to `asm!()` is a macro call
Fixes#129503
When the argument to `asm!()` is a macro call, e.g. `asm!(concat!("abc", "{} pqr"))`, and there's an error in the resulting template string, we do not take into account the presence of this macro call while computing the error span. This PR fixes that. Now we will use the entire thing between the parenthesis of `asm!()` as the error span in this situation e.g. for `asm!(concat!("abc", "{} pqr"))` the error span will be `concat!("abc", "{} pqr")`.
When the template string passed to asm!() is produced by
a macro call like concat!() we were producing wrong error
spans. Now in the case of a macro call we just use the entire
arg to asm!(), macro call and all, as the error span.
- Replace non-standard names like 's, 'p, 'rg, 'ck, 'parent, 'this, and
'me with vanilla 'a. These are cases where the original name isn't
really any more informative than 'a.
- Replace names like 'cx, 'mir, and 'body with vanilla 'a when the lifetime
applies to multiple fields and so the original lifetime name isn't
really accurate.
- Put 'tcx last in lifetime lists, and 'a before 'b.
Simplify some nested `if` statements
Applies some but not all instances of `clippy::collapsible_if`. Some ended up looking worse afterwards, though, so I left those out. Also applies instances of `clippy::collapsible_else_if`
Review with whitespace disabled please.
Fix false positive with `missing_docs` and `#[test]`
Since #130025, the compiler don't ignore missing_docs when compiling the tests. But there is now a false positive warning for every `#[test]`
For example, this code
```rust
//! Crate docs
fn just_a_test() {}
```
Would emit this warning when running `cargo test`
```
warning: missing documentation for a constant
--> src/lib.rs:5:1
|
4 | #[test]
| ------- in this procedural macro expansion
5 | fn just_a_test() {}
| ^^^^^^^^^^^^^^^^^^^
```
Since #130025, the compiler don't ignore missing_docs when compiling the tests.
But there is now a false positive warning for every `#[test]`
For example, this code
```rust
//! Crate docs
fn just_a_test() {}
```
Would emit this warning when running `cargo test`
```
warning: missing documentation for a constant
--> src/lib.rs:5:1
|
4 | #[test]
| ------- in this procedural macro expansion
5 | fn just_a_test() {}
| ^^^^^^^^^^^^^^^^^^^
```
Also emit `missing_docs` lint with `--test` to fulfil expectations
This PR removes the "test harness" suppression of the `missing_docs` lint to be able to fulfil `#[expect]` (expectations) as it is now "relevant".
I think the goal was to maybe avoid false-positive while linting on public items under `#[cfg(test)]` but with effective visibility we should no longer have any false-positive.
Another possibility would be to query the lint level and only emit the lint if it's of expect level, but that is even more hacky.
Fixes https://github.com/rust-lang/rust/issues/130021
try-job: x86_64-gnu-aux
in this commit, `naked_asm!` is an alias for `asm!` with one difference: `options(noreturn)` is always enabled by `naked_asm!`. That makes it future-compatible for when `naked_asm!` starts disallowing `options(noreturn)` later.
debug-fmt-detail option
I'd like to propose a new option that makes `#[derive(Debug)]` generate no-op implementations that don't print anything, and makes `{:?}` in format strings a no-op.
There are a couple of motivations for this:
1. A more thorough stripping of debug symbols. Binaries stripped of debug symbols still retain some of them through `Debug` implementations. It's hard to avoid that without compiler's help, because debug formatting can be used in many places, including dependencies, and their loggers, asserts, panics, etc.
* In my testing it gives about 2% binary size reduction on top of all other binary-minimizing best practices (including `panic_immediate_abort`). There are targets like Web WASM or embedded where users pay attention to binary sizes.
* Users distributing closed-source binaries may not want to "leak" any symbol names as a matter of principle.
2. Adds ability to test whether code depends on specifics of the `Debug` format implementation in unwise ways (e.g. trying to get data unavailable via public interface, or using it as a serialization format). Because current Rust's debug implementation doesn't change, there's a risk of it becoming a fragile de-facto API that [won't be possible to change in the future](https://www.hyrumslaw.com/). An option that "breaks" it can act as a [grease](https://www.rfc-editor.org/rfc/rfc8701.html).
This implementation is a `-Z fmt-debug=opt` flag that takes:
* `full` — the default, current state.
* `none` — makes derived `Debug` and `{:?}` no-ops. Explicit `impl Debug for T` implementations are left unharmed, but `{:?}` format won't use them, so they may get dead-code eliminated if they aren't invoked directly.
* `shallow` — makes derived `Debug` print only the type's name, without recursing into fields. Fieldless enums print their variant names. `{:?}` works.
The `shallow` option is a compromise between minimizing the `Debug` code, and compatibility. There are popular proc-macro crates that use `Debug::fmt` as a way to convert enum values into their Rust source code.
There's a corresponding `cfg` flag: `#[cfg(fmt_debug = "none")]` that can be used in user code to react to this setting to minimize custom `Debug` implementations or remove unnecessary formatting helper functions.
derive(SmartPointer): assume pointee from the single generic and better error messages
Fix#129465
Actually RFC says that `#[pointee]` can be inferred when there is no ambiguity, or there is only one generic type parameter so to say.
cc ```@Darksonn```
r? ```@compiler-errors```
Add `#[warn(unreachable_pub)]` to a bunch of compiler crates
By default `unreachable_pub` identifies things that need not be `pub` and tells you to make them `pub(crate)`. But sometimes those things don't need any kind of visibility. So they way I did these was to remove the visibility entirely for each thing the lint identifies, and then add `pub(crate)` back in everywhere the compiler said it was necessary. (Or occasionally `pub(super)` when context suggested that was appropriate.) Tedious, but results in more `pub` removal.
There are plenty more crates to do but this seems like enough for a first PR.
r? `@compiler-errors`
Stabilize `unsafe_attributes`
# Stabilization report
## Summary
This is a tracking issue for the RFC 3325: unsafe attributes
We are stabilizing `#![feature(unsafe_attributes)]`, which makes certain attributes considered 'unsafe', meaning that they must be surrounded by an `unsafe(...)`, as in `#[unsafe(no_mangle)]`.
RFC: rust-lang/rfcs#3325
Tracking issue: #123757
## What is stabilized
### Summary of stabilization
Certain attributes will now be designated as unsafe attributes, namely, `no_mangle`, `export_name`, and `link_section` (stable only), and these attributes will need to be called by surrounding them in `unsafe(...)` syntax. On editions prior to 2024, this is simply an edition lint, but it will become a hard error in 2024. This also works in `cfg_attr`, but `unsafe` is not allowed for any other attributes, including proc-macros ones.
```rust
#[unsafe(no_mangle)]
fn a() {}
#[cfg_attr(any(), unsafe(export_name = "c"))]
fn b() {}
```
For a table showing the attributes that were considered to be included in the list to require unsafe, and subsequent reasoning about why each such attribute was or was not included, see [this comment here](https://github.com/rust-lang/rust/pull/124214#issuecomment-2124753464)
## Tests
The relevant tests are in `tests/ui/rust-2024/unsafe-attributes` and `tests/ui/attributes/unsafe`.
Use more slice patterns inside the compiler
Nothing super noteworthy. Just replacing the common 'fragile' pattern of "length check followed by indexing or unwrap" with slice patterns for legibility and 'robustness'.
r? ghost
improve error message when `global_asm!` uses `asm!` operands
follow-up to https://github.com/rust-lang/rust/pull/128207
what was
```
error: expected expression, found keyword `in`
--> src/lib.rs:1:31
|
1 | core::arch::global_asm!("{}", in(reg));
| ^^ expected expression
```
becomes
```
error: the `in` operand cannot be used with `global_asm!`
--> $DIR/parse-error.rs:150:19
|
LL | global_asm!("{}", in(reg));
| ^^ the `in` operand is not meaningful for global-scoped inline assembly, remove it
```
the span of the error is just the keyword, which means that we can't create a machine-applicable suggestion here. The alternative would be to attempt to parse the full operand, but then if there are syntax errors in the operand those would be presented to the user, even though the parser already knows that the output won't be valid. Also that would require more complexity in the parser.
So I think this is a nice improvement at very low cost.
More unsafe attr verification
This code denies unsafe on attributes such as `#[test]` and `#[ignore]`, while also changing the `MetaItem` parsing so `unsafe` in args like `#[allow(unsafe(dead_code))]` is not accidentally allowed.
Tracking:
- https://github.com/rust-lang/rust/issues/123757
When collecting tokens there are two kinds of range:
- a range relative to the parser's full token stream (which we get when
we are parsing);
- a range relative to a single AST node's token stream (which we use
within `LazyAttrTokenStreamImpl` when replacing tokens).
These are currently both represented with `Range<u32>` and it's easy to
mix them up -- until now I hadn't properly understood the difference.
This commit introduces `ParserRange` and `NodeRange` to distinguish
them. This also requires splitting `ReplaceRange` in two, giving the new
types `ParserReplacement` and `NodeReplacement`. (These latter two names
reduce the overloading of the word "range".)
The commit also rewrites some comments to be clearer.
The end result is a little more verbose, but much clearer.
derive(SmartPointer): rewrite bounds in where and generic bounds
Fix#127647
Due to the `Unsize` bounds, we need to commute the bounds on the pointee type to the new self type.
cc ```@Darksonn```
This makes it possible for the `unsafe(...)` syntax to only be
valid at the top level, and the `NestedMetaItem`s will automatically
reject `unsafe(...)`.
Mark `Parser::eat`/`check` methods as `#[must_use]`
These methods return a `bool`, but we probably should either use these values or explicitly throw them away (e.g. when we just want to unconditionally eat a token if it exists).
I changed a few places from `eat` to `expect`, but otherwise I tried to leave a comment explaining why the `eat` was okay.
This also adds a test for the `pattern_type!` macro, which used to silently accept a missing `is` token.
`#[naked]`: report incompatible attributes
tracking issue: https://github.com/rust-lang/rust/issues/90957
this is a re-implementation of https://github.com/rust-lang/rust/pull/93809 by ``@bstrie`` which was closed 2 years ago due to inactivity.
This PR takes some of the final comments into account, specifically providing a little more context in error messages, and using an allow list to determine which attributes are compatible with `#[naked]`.
Notable attributes that are incompatible with `#[naked]` are:
* `#[inline]`
* `#[track_caller]`
* ~~`#[target_feature]`~~ (this is now allowed, see PR discussion)
* `#[test]`, `#[ignore]`, `#[should_panic]`
These attributes just directly conflict with what `#[naked]` should do.
Naked functions are still important for systems programming, embedded, and operating systems, so I'd like to move them forward.
improve error message when `global_asm!` uses `asm!` options
specifically, what was
error: expected one of `)`, `att_syntax`, or `raw`, found `preserves_flags`
--> $DIR/bad-options.rs:45:25
|
LL | global_asm!("", options(preserves_flags));
| ^^^^^^^^^^^^^^^ expected one of `)`, `att_syntax`, or `raw`
is now
error: the `preserves_flags` option cannot be used with `global_asm!`
--> $DIR/bad-options.rs:45:25
|
LL | global_asm!("", options(preserves_flags));
| ^^^^^^^^^^^^^^^ the `preserves_flags` option is not meaningful for global-scoped inline assembly
mirroring the phrasing of the [reference](https://doc.rust-lang.org/reference/inline-assembly.html#options).
This is also a bit of a refactor for a future `naked_asm!` macro (for use in `#[naked]` functions). Currently this sort of error can come up when switching from inline to global asm, or when a user just isn't that experienced with assembly. With `naked_asm!` added to the mix hitting this error is more likely.
- merge error codes
- use attribute name that is incompatible in error message
- add test for conditional incompatible attribute
- add `linkage` to the allowlist
