Remove restriction on type parameters preceding consts w/ feature const-generics
Removed the restriction on type parameters preceding const parameters when the feature const-generics is enabled.
Builds on #74676, which deals with unsorted generic parameters. This just lifts the check in lowering the AST to HIR that permits consts and types to be reordered with respect to each other. Lifetimes still must precede both
This change is not intended for min-const-generics, and is gated behind the `#![feature(const_generics)]`.
One thing is that it also permits type parameters without a default to come after consts, which I expected to not work, and was hoping to get more guidance on whether that should be permitted or how to prevent it otherwise.
I did not go through the RFC process for this pull request because there was prior work to get this feature added. In the previous PR that was cited, work was done to enable this change.
r? @lcnr
Rollup of 8 pull requests
Successful merges:
- #74200 (Std panicking unsafe block in unsafe fn)
- #75286 (Add additional case for Path starts with)
- #75318 (Resolve `char` as a primitive even if there is a module in scope)
- #75320 (Detect likely `for foo of bar` JS syntax)
- #75328 (Cleanup E0749)
- #75344 (Rename "Important traits" to "Notable traits")
- #75348 (Move to intra-doc links in library/core/src/time.rs)
- #75350 (Do not ICE when lowering invalid extern fn with bodies)
Failed merges:
r? @ghost
Fixes#74800
The definition of `is_x86_feature_detected!` (and similar macros)
depends on the platform - it is produced by a `cfg_if!` invocation on
x86, and a plain `#[cfg]` on other platforms. Since it is part of the
prelude, we will end up importing different hygiene information
depending on the platform. This previously required us to avoid printing raw
`SyntaxContext` ids in any tests that uses the standard library, since
the captured output will be platform-dependent.
Previously, we replaced all `SyntaxContext` ids with "#CTXT", and the
raw `Span` lo/hi bytes with "LO..HI".
This commit adds `#![no_std]` and `extern crate std` to all proc-macro
tests that print spans. This suppresses the prelude import, while
still using lang items from `std` (which gives us a buildable binary).
With this apporach, we will only load hygiene information for things
which we explicitly import. This lets us re-add
`-Z unpretty=expanded,hygiene`, since its output can now be made stable
across all platforms.
Additionally, we use `-Z span-debug` in more places, which lets us avoid
the "LO..HI" normalization hack.
Updated tests and error msgs
Update stderr from test
Update w/ lcnr comments
Change some tests around, and also updated Ord implementation for ParamKindOrd
Update w/ nits from lcnr
Added this test to ensure that reordering the parameters only works with the feature const
generics enabled.
Fixed nits
Also added another test to verify that intermixed lifetimes are forbidden
polymorphize: unevaluated constants
This PR makes polymorphization visit the promoted MIR of unevaluated constants with available promoted MIR instead of visiting the substitutions of that constant - which will mark all of the generic parameters as used; in addition polymorphization will now visit non-promoted unevaluated constants rather than visit their substs.
r? @lcnr
Emit == null instead of <= null for niche check
When the niche maximum is zero, emit a "== zero" check instead of a "<= zero" check. In particular, this avoids the awkward case of "<= null". While LLVM does canonicalize this to "== null", this apparently doesn't happen for constant expressions, leading to the issue in #74425. While that can be addressed on the LLVM side, it still seems prudent to emit sensible IR here, because this will allow null checks to be optimized earlier in the pipeline.
Fixes#74425.
When the niche maximum is zero, emit a "== zero" check instead of
a "<= zero" check. In particular, this avoid the awkward case of
"<= null". While LLVM does canonicalize this to "!= null", this
appently doesn't happen for constant expressions, leading to the
issue in #74425. While that can be addressed on the LLVM side, it
still seems prudent to emit sensible IR here, because this will
allow null checks to be optimized earlier in the pipeline.
Fixes#74425.
Display elided lifetime for non-reference type in doc
In edition 2018 we encourage writing `<'_>` explicitly, so rustdoc should display like such as well.
Fixes#75225
~~Somehow when I run the compiled rustdoc using `cargo +stage2 doc` on other crates, it correctly produces `<'_>`, but I couldn't get the std doc to do the same with `./x.py doc --stage 2`. Might this be related to the recent change to x.py about how the doc is built?~~
Don't call a function in function-arguments-naked.rs
Fixes#75096
It's U.B. to use anything other than inline assmebling in a naked
function. Fortunately, the `#break` directive works fine without
anything in the function body.
By moving `{known,used}_attrs` from `SessionGlobals` to `Session`. This
means they are accessed via the `Session`, rather than via TLS. A few
`Attr` methods and `librustc_ast` functions are now methods of
`Session`.
All of this required passing a `Session` to lots of functions that didn't
already have one. Some of these functions also had arguments removed, because
those arguments could be accessed directly via the `Session` argument.
`contains_feature_attr()` was dead, and is removed.
Some functions were moved from `librustc_ast` elsewhere because they now need
to access `Session`, which isn't available in that crate.
- `entry_point_type()` --> `librustc_builtin_macros`
- `global_allocator_spans()` --> `librustc_metadata`
- `is_proc_macro_attr()` --> `Session`
Implement the `min_const_generics` feature gate
Implements both https://github.com/rust-lang/lang-team/issues/37 and https://github.com/rust-lang/compiler-team/issues/332.
Adds the new feature gate `#![feature(min_const_generics)]`.
This feature gate adds the following limitations to using const generics:
- generic parameters must only be used in types if they are trivial. (either `N` or `{ N }`)
- generic parameters must be either integers, `bool` or `char`.
We do allow arbitrary expressions in associated consts though, meaning that the following is allowed,
even if `<[u8; 0] as Foo>::ASSOC` is not const evaluatable.
```rust
trait Foo {
const ASSOC: usize;
}
impl<const N: usize> Foo for [u8; N] {
const ASSOC: usize = 64 / N;
}
```
r? @varkor cc @eddyb @withoutboats
Prevent `__rust_begin_short_backtrace` frames from being tail-call optimised away
I've stumbled across some situations where there (unexpectedly) was no `__rust_begin_short_backtrace` frame on the stack during unwinding.
On closer examination, it appeared that the calls to that function had been tail-call optimised away.
This PR follows [@bjorn3's suggestion on Zulip](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Disabling.20tail.20call.20optimisation.3F/near/205699133), by adding calls to `black_box` that hint to rustc not to perform TCO.
Fixes#47429
instance: polymorphize upvar closures/generators
This PR modifies how instances are polymorphized so that closures and generators have any closures or generators captured within their upvars also polymorphized.
With the new symbol mangling, a fully polymorphised closure will produce the same symbol regardless of what it was instantiated with. However, when that polymorphised closure captures another closure as an upvar, then the type of that other closure in the upvar substitution wouldn't have been polymorphised. The other closure will still refer to the initial substitutions. Therefore, the polymorphised closure will end up hashing differently but producing the same symbol - triggering `assert_symbols_are_distinct` in MIR partitioning. The old mangling scheme had a hash at the end that meant this didn't happen (this would still have been an issue, we just didn't have a way to notice).
See [this Zulip discussion for further elaboration](https://rust-lang.zulipchat.com/#narrow/stream/216091-t-compiler.2Fwg-polymorphization/topic/symbol.20mangling.20v0.20.E2.9C.95.20polymorphisation/near/206152008).
r? @eddyb
cc @lcnr
By always polymorphizing substitutions, functions which take closures as
arguments (e.g. `impl Fn()`) can have fewer mono items when some of the
argument closures can be polymorphized.
Signed-off-by: David Wood <david@davidtw.co>
This commit modifies how instances are polymorphized so that closures
and generators have any closures or generators captured within their
upvars also polymorphized - this avoids symbol clashes with the new
symbol mangling scheme.
Signed-off-by: David Wood <david@davidtw.co>
This commit makes polymorphization visit non-promoted unevaluated
constants rather than visit their substs directly.
Signed-off-by: David Wood <david@davidtw.co>
Check whether locals are too large instead of whether accesses into them are too large
Essentially this stops const prop from attempting to optimize
```rust
let mut x = [0_u8; 5000];
x[42] = 3;
```
I don't expect this to be a perf improvement without #73656 (which is also where the lack of this PR will be a perf regression).
r? @wesleywiser
This commit makes polymorphization visited the MIR of unevaluated
constants with available promoted MIR instead of visiting the
substitutions of that constant - which will mark all of the generic
parameters as used.
Signed-off-by: David Wood <david@davidtw.co>
rustc_ast: Stop using "string typing" for doc comment tokens
Explicitly store their kind and style retrieved during lexing in the `token::DocComment`.
Also don't "beautify" doc comments before converting them to `#[doc]` attributes when passing them to macros (both declarative and procedural).
The trimming of empty lines, lines containing only `*`s, etc is purely a rustdoc's job as a part of its presentation of doc strings to users, rustc must not do this and must pass tokens as precisely as possible internally.
Make `IntoIterator` lifetime bounds of `&BTreeMap` match with `&HashMap`
This is a pretty small change on the lifetime bounds of `IntoIterator` implementations of both `&BTreeMap` and `&mut BTreeMap`. This is loosening the lifetime bounds, so more code should be accepted with this PR. This is lifetime bounds will still be implicit since we have `type Item = (&'a K, &'a V);` in the implementation. This change will make the HashMap and BTreeMap share the same signature, so we can share the same function/trait with both HashMap and BTreeMap in the code.
Fixes#74034.
r? @dtolnay hey, I was touching this file on my previous PR and wanted to fix this on the way. Would you mind taking a look at this, or redirecting it if you are busy?
