Match against attribute name when validating attributes
Extract attribute name once and match it against symbols that are being
validated, instead of using `Session::check_name` for each symbol
individually.
Assume that all validated attributes are used, instead of marking them
as such, since the attribute check should be exhaustive.
Stablize `non-ascii-idents`
This is the stablization PR for RFC 2457. Currently this is waiting on fcp in [tracking issue](https://github.com/rust-lang/rust/issues/55467).
r? `@Manishearth`
Don't set fast-math for the SIMD operations we set it for previously
Instead of `fast-math`. `fast-math` implies things like functions not
being able to accept as an argument or return as a result, say, `inf`
which made these functions confusingly named or behaving incorrectly,
depending on how you interpret it. It seems that the intended behaviour
was to set a `afn` flag instead. In doing so we also renamed the
intrinsics to say `_approx` so that it is clear these are not precision
oriented and the users can act accordingly.
Fixes#84268
`continue` statements were missing coverage. This was particularly
noticeable in a match pattern that contained only a `continue`
statement, leaving the branch appear uncounted. This PR addresses the
problem and adds tests to prove it.
`fast-math` implies things like functions not being able to accept as an
argument or return as a result, say, `inf` which made these functions
confusingly named or behaving incorrectly, depending on how you
interpret it. Since the time when these intrinsics have been implemented
the intrinsics user's (stdsimd) approach has changed significantly and
so now it is required that these intrinsics operate normally rather than
in "whatever" way.
Fixes#84268
fix incomplete diagnostic notes when closure returns conflicting for genric type
fixes#84128
Correctly report the span on for conflicting return type in closures
Builtin derive macros: fix error with const generics default
This fixes a bug where builtin derive macros (like Clone, Debug) would basically copy-paste the default from a const generic, causing a compile error with very confusing message - it would say defaults are not allowed in impl blocks, while pointing at struct/enum/union definition.
Detect when suggested paths enter extern crates more rigorously
When reporting resolution errors, the compiler tries to avoid suggesting importing inaccessible paths from other crates. However, the search for suggestions only recognized when it was entering a crate root directly, and so failed to recognize a path like `crate::module::private_item`, where `module` was imported from another crate with `use other_crate::module`, as entering another crate.
Fixes#80079Fixes#84081
Compiler error messages: reduce assertiveness of message E0384
This message is emitted as guidance by the compiler when a developer attempts to reassign a value to an immutable variable. Following the message will always currently work, but it may not always be the best course of action; following the 'consider ...' messaging pattern provides a hint to the developer that it could be wise to explore other alternatives.
Resolves#84144
Remove #[main] attribute.
This removes the #[main] attribute support from the compiler according to the decisions within #29634. For existing use cases within test harness generation, replaced it with a newly-introduced internal attribute `#[rustc_main]`.
This is first part extracted from #84062 .
Closes#29634.
r? `@petrochenkov`
Add simd_{round,trunc} intrinsics
LLVM supports many functions from math.h in its IR. Many of these
have SIMD instructions on various platforms. So, let's add round and
trunc so std::arch can use them.
Yes, exact comparison is intentional: rounding must always return a
valid integer-equal value, except for inf/NAN.
Update docs for unsafe_op_in_unsafe_fn stability.
The unsafe_op_in_unsafe_fn lint was stabilized in #79208, but the bottom of this documentation wasn't updated.
I'm just guessing at the reason here, hopefully it is close to correct. The only discussion I found is https://github.com/rust-lang/rust/issues/71668#issuecomment-730399862 which didn't really explain the thought process behind the decision.
LLVM supports many functions from math.h in its IR. Many of these have
single-instruction variants on various platforms. So, let's add them so
std::arch can use them.
Yes, exact comparison is intentional: rounding must always return a
valid integer-equal value, except for inf/NAN.
add lint deref_nullptr detecting when a null ptr is dereferenced
fixes#83856
changelog: add lint that detect code like
```rust
unsafe {
&*core::ptr::null::<i32>()
};
unsafe {
addr_of!(std::ptr::null::<i32>())
};
let x: i32 = unsafe {*core::ptr::null()};
let x: i32 = unsafe {*core::ptr::null_mut()};
unsafe {*(0 as *const i32)};
unsafe {*(core::ptr::null() as *const i32)};
```
```
warning: Dereferencing a null pointer causes undefined behavior
--> src\main.rs:5:26
|
5 | let x: i32 = unsafe {*core::ptr::null()};
| ^^^^^^^^^^^^^^^^^^
| |
| a null pointer is dereferenced
| this code causes undefined behavior when executed
|
= note: `#[warn(deref_nullptr)]` on by default
```
Limitation:
It does not detect code like
```rust
const ZERO: usize = 0;
unsafe {*(ZERO as *const i32)};
```
or code where `0` is not directly a literal
Avoid an `Option<Option<_>>`
By simply swapping the calls to `map` and `and_then` around the complexity of
handling an `Option<Option<_>>` disappears.
`@rustbot` modify labels +C-cleanup +T-compiler
Fix typo in error message
Also tweaked the message a bit by
- removing the hyphen, because in my opinion the hyphen makes the
message a bit harder to read, especially combined with the backticks;
- adding the word "be", because I think it's a bit clearer that way.
This message is emitted as guidance by the compiler when a developer attempts to reassign a value to an immutable variable. Following the message will always currently work, but it may not always be the best course of action; following the 'consider ...' messaging pattern provides a hint to the developer that it could be wise to explore other alternatives.
Also tweaked the message a bit by
- removing the hyphen, because in my opinion the hyphen makes the
message a bit harder to read, especially combined with the backticks;
- adding the word "be", because I think it's a bit clearer that way.
Improve trait/impl method discrepancy errors
* Use more accurate spans
* Clean up some code by removing previous hack
* Provide structured suggestions
Structured suggestions are particularly useful for cases where arbitrary self types are used, like in custom `Future`s, because the way to write `self: Pin<&mut Self>` is not necessarily self-evident when first encountered.
Issue 81508 fix
Fix#81508
**Problem**: When variable name is used incorrectly as path, error and warning point to undeclared/unused name, when in fact the name is used, just incorrectly (should be used as a variable, not part of a path).
**Summary for fix**: When path resolution errs, diagnostics checks for variables in ```ValueNS``` that have the same name (e.g., variable rather than path named Foo), and adds additional suggestion that user may actually intend to use the variable name rather than a path.
The fix does not suppress or otherwise change the *warning* that results. I did not find a straightforward way in the code to modify this, but would love to make changes here as well with any guidance.
This PR modifies the macro expansion infrastructure to handle attributes
in a fully token-based manner. As a result:
* Derives macros no longer lose spans when their input is modified
by eager cfg-expansion. This is accomplished by performing eager
cfg-expansion on the token stream that we pass to the derive
proc-macro
* Inner attributes now preserve spans in all cases, including when we
have multiple inner attributes in a row.
This is accomplished through the following changes:
* New structs `AttrAnnotatedTokenStream` and `AttrAnnotatedTokenTree` are introduced.
These are very similar to a normal `TokenTree`, but they also track
the position of attributes and attribute targets within the stream.
They are built when we collect tokens during parsing.
An `AttrAnnotatedTokenStream` is converted to a regular `TokenStream` when
we invoke a macro.
* Token capturing and `LazyTokenStream` are modified to work with
`AttrAnnotatedTokenStream`. A new `ReplaceRange` type is introduced, which
is created during the parsing of a nested AST node to make the 'outer'
AST node aware of the attributes and attribute target stored deeper in the token stream.
* When we need to perform eager cfg-expansion (either due to `#[derive]` or `#[cfg_eval]`),
we tokenize and reparse our target, capturing additional information about the locations of
`#[cfg]` and `#[cfg_attr]` attributes at any depth within the target.
This is a performance optimization, allowing us to perform less work
in the typical case where captured tokens never have eager cfg-expansion run.
Extract attribute name once and match it against symbols that are being
validated, instead of using `Session::check_name` for each symbol
individually.
Assume that all validated attributes are used, instead of marking them
as such, since the attribute check should be exhaustive.
Expand derive invocations in left-to-right order
While derives were being collected in left-to-order order, the
corresponding `Invocation`s were being pushed in the wrong order.
Avoid `;` -> `,` recovery and unclosed `}` recovery from being too verbose
Those two recovery attempts have a very bad interaction that causes too
unnecessary output. Add a simple gate to avoid interpreting a `;` as a
`,` when there are unclosed braces.
Fix#83498.
Categorize and explain target features support
There are 3 different uses of the `-C target-feature` args passed to rustc:
1. All of the features are passed to LLVM, which uses them to configure code-generation. This is sort-of stabilized since 1.0 though LLVM does change/add/remove target features regularly.
2. Target features which are in [the compiler's allowlist](69e1d22ddb/compiler/rustc_codegen_ssa/src/target_features.rs (L12-L34)) can be used in `cfg!(target_feature)` etc. These may have different names than in LLVM and are renamed before passing them to LLVM.
3. Target features which are in the allowlist and which are stabilized or feature-gate-enabled can be used in `#[target_feature]`.
It can be confusing that `rustc --print target-features` just prints out the LLVM features without separating out the rustc features or even mentioning that the dichotomy exists.
This improves the situation by separating out the rustc and LLVM target features and adding a brief explanation about the difference.
Abbreviated Example Output:
```
$ rustc --print target-features
Features supported by rustc for this target:
adx - Support ADX instructions.
aes - Enable AES instructions.
...
xsaves - Support xsaves instructions.
crt-static - Enables libraries with C Run-time Libraries(CRT) to be statically linked.
Code-generation features supported by LLVM for this target:
16bit-mode - 16-bit mode (i8086).
32bit-mode - 32-bit mode (80386).
...
x87 - Enable X87 float instructions.
xop - Enable XOP instructions.
Use +feature to enable a feature, or -feature to disable it.
For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2
Code-generation features cannot be used in cfg or #[target_feature],
and may be renamed or removed in a future version of LLVM or rustc.
```
Motivated by #83975.
CC https://github.com/rust-lang/rust/issues/49653
Those two recovery attempts have a very bad interaction that causes too
unnecessary output. Add a simple gate to avoid interpreting a `;` as a
`,` when there are unclosed braces.
Don't concatenate binders across types
Partially addresses #83737
There's actually two issues that I uncovered in #83737. The first is that we are concatenating bound vars across types, i.e. in
```
F: Fn(&()) -> &mut (dyn Future<Output = ()> + Unpin)
```
the bound vars on `Future` get set as `for<anon>` since those are the binders on `Fn(&()`. This is obviously wrong, since we should only concatenate directly nested trait refs. This is solved here by introducing a new `TraitRefBoundary` scope, that we put around the "syntactical" trait refs and basically don't allow concatenation across.
Now, this alone *shouldn't* be a super terrible problem. At least not until you consider the other issue, which is a much more elusive and harder to design a "perfect" fix. A repro can be seen in:
```
use core::future::Future;
async fn handle<F>(slf: &F)
where
F: Fn(&()) -> &mut (dyn for<'a> Future<Output = ()> + Unpin),
{
(slf)(&()).await;
}
```
Notice the `for<'a>` around `Future`. Here, `'a` is unused, so the `for<'a>` Binder gets changed to a `for<>` Binder in the generator witness, but the "local decl" still has it. This has heavy intersections with region anonymization and erasing. Luckily, it's not *super* common to find this unique set of circumstances. It only became apparently because of the first issue mentioned here. However, this *is* still a problem, so I'm leaving #83737 open.
r? `@nikomatsakis`
The issue was that the resulting debuginfo was too complex for LLVM to
translate into CodeView records correctly. As a result, it simply
ignored the debuginfo which meant Windows debuggers could not display
any closed over variables when stepping inside a closure.
This fixes that by spilling additional variables to the stack so that
the resulting debuginfo is simple (just `*my_variable.dbg.spill`) and
LLVM can generate the correct CV records.
This commit implements the idea of a new ABI for the WebAssembly target,
one called `"wasm"`. This ABI is entirely of my own invention
and has no current precedent, but I think that the addition of this ABI
might help solve a number of issues with the WebAssembly targets.
When `wasm32-unknown-unknown` was first added to Rust I naively
"implemented an abi" for the target. I then went to write `wasm-bindgen`
which accidentally relied on details of this ABI. Turns out the ABI
definition didn't match C, which is causing issues for C/Rust interop.
Currently the compiler has a "wasm32 bindgen compat" ABI which is the
original implementation I added, and it's purely there for, well,
`wasm-bindgen`.
Another issue with the WebAssembly target is that it's not clear to me
when and if the default C ABI will change to account for WebAssembly's
multi-value feature (a feature that allows functions to return multiple
values). Even if this does happen, though, it seems like the C ABI will
be guided based on the performance of WebAssembly code and will likely
not match even what the current wasm-bindgen-compat ABI is today. This
leaves a hole in Rust's expressivity in binding WebAssembly where given
a particular import type, Rust may not be able to import that signature
with an updated C ABI for multi-value.
To fix these issues I had the idea of a new ABI for WebAssembly, one
called `wasm`. The definition of this ABI is "what you write
maps straight to wasm". The goal here is that whatever you write down in
the parameter list or in the return values goes straight into the
function's signature in the WebAssembly file. This special ABI is for
intentionally matching the ABI of an imported function from the
environment or exporting a function with the right signature.
With the addition of a new ABI, this enables rustc to:
* Eventually remove the "wasm-bindgen compat hack". Once this
ABI is stable wasm-bindgen can switch to using it everywhere.
Afterwards the wasm32-unknown-unknown target can have its default ABI
updated to match C.
* Expose the ability to precisely match an ABI signature for a
WebAssembly function, regardless of what the C ABI that clang chooses
turns out to be.
* Continue to evolve the definition of the default C ABI to match what
clang does on all targets, since the purpose of that ABI will be
explicitly matching C rather than generating particular function
imports/exports.
Naturally this is implemented as an unstable feature initially, but it
would be nice for this to get stabilized (if it works) in the near-ish
future to remove the wasm32-unknown-unknown incompatibility with the C
ABI. Doing this, however, requires the feature to be on stable because
wasm-bindgen works with stable Rust.
Remove the insta-stable `cfg(wasm)`
The addition of `cfg(wasm)` was an oversight on my end that turns out to have a number
of downsides:
* It was introduced as an insta-stable addition, forgoing the usual
staging mechanism we use for potentially far-reaching changes;
* It is a breaking change for people who are using `--cfg wasm` either
directly or via cargo for other purposes;
* It is not entirely clear if a bare `wasm` cfg is a right option or
whether `wasm` family of targets are special enough to warrant
special-casing these targets specifically.
As for the last point, there appears to be a fair amount of support for
reducing the boilerplate in specifying architectures from the same
family, while ignoring their pointer width. The suggested way forward
would be to propose such a change as a separate RFC as it is potentially
a quite contentious addition.
cc #83879 `@devsnek`
Add more info for common trait resolution and async/await errors
* Suggest `Pin::new`/`Box::new`/`Arc::new`/`Box::pin` in more cases
* Point at `impl` and type defs introducing requirements on E0277
The addition of `cfg(wasm)` was an oversight on my end that has a number
of downsides:
* It was introduced as an insta-stable addition, forgoing the usual
staging mechanism we use for potentially far-reaching changes;
* It is a breaking change for people who are using `--cfg wasm` either
directly or via cargo for other purposes;
* It is not entirely clear if a bare `wasm` cfg is a right option or
whether `wasm` family of targets are special enough to warrant
special-casing these targets specifically.
As for the last point, there appears to be a fair amount of support for
reducing the boilerplate in specifying architectures from the same
family, while ignoring their pointer width. The suggested way forward
would be to propose such a change as a separate RFC as it is potentially
a quite contentious addition.
Stabilize cmp_min_max_by
I would like to propose cmp::{min_by, min_by_key, max_by, max_by_key}
for stabilization.
These are relatively simple and seemingly uncontroversial functions and
have been unchanged in unstable for a while now.
Closes: #64460
Rollup of 8 pull requests
Successful merges:
- #83476 (Add strong_count mutation methods to Rc)
- #83634 (Do not emit the advanced diagnostics on macros)
- #83816 (Trigger `unused_doc_comments` on macros at once)
- #83916 (Use AnonConst for asm! constants)
- #83935 (forbid `impl Trait` in generic param defaults)
- #83936 (Disable using non-ascii identifiers in extern blocks.)
- #83945 (Add suggestion to reborrow mutable references when they're moved in a for loop)
- #83954 (Do not ICE when closure is involved in Trait Alias Impl Trait)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
I would like to propose cmp::{min_by, min_by_key, max_by, max_by_key}
for stabilization.
These are relatively simple and seemingly uncontroversial functions and
have been unchanged in unstable for a while now.
use a `SmallVec` in `impl_or_trait_item`
#83293 showed that this is fairly hot, slightly improves max-rss and cpu cycles, does not noticeably improve instruction counts
forbid `impl Trait` in generic param defaults
Fixes#83929
Forbid using `impl Trait` in the default types of generic parameters, e.g. `struct Foo<T = impl Trait>`. I assume this was never supposed to be allowed - it seems no UI test used it.
Note that using `impl Trait` in this position did not hit a feature gate error; however, this *shouldn't* be a breaking change as any attempt to use it should have hit the ICE in #83929 and/or failed to provide a defining use of the `impl Trait`.
Use AnonConst for asm! constants
This replaces the old system which used explicit promotion. See #83169 for more background.
The syntax for `const` operands is still the same as before: `const <expr>`.
Fixes#83169
Because the implementation is heavily based on inline consts, we suffer from the same issues:
- We lose the ability to use expressions derived from generics. See the deleted tests in `src/test/ui/asm/const.rs`.
- We are hitting the same ICEs as inline consts, for example #78174. It is unlikely that we will be able to stabilize this before inline consts are stabilized.
Add `FromIterator` and `IntoIterator` impls for `ThinVec`
These should make using `ThinVec` feel much more like using `Vec`.
They will allow users of `Vec` to switch to `ThinVec` while continuing
to use `collect()`, `for` loops, and other parts of the iterator API.
I don't know if there were use cases before for using the iterator API
with `ThinVec`, but I would like to start using `ThinVec` in rustdoc,
and having it conform to the iterator API would make the transition
*a lot* easier.
I added a `FromIterator` impl, an `IntoIterator` impl that yields owned
elements, and `IntoIterator` impls that yield immutable or mutable
references to elements. I also added some unit tests for `ThinVec`.
Find codegen backends in more locations
* Search in the sysroot passed using `--sysroot` in addition to the default sysroot.
* Search for `librustc_codegen_$name.so` in addition to `librustc_codegen_$name-$release.so`.
This combined would allow putting `librustc_codegen_cranelift.so` in the right location of a sysroot passed using `--sysroot`.
Allow specifying alignment for functions
Fixes#75072
This allows the user to specify alignment for functions, which can be useful for low level work where functions need to necessarily be aligned to a specific value.
I believe the error cases not covered in the match are caught earlier based on my testing so I had them just return `None`.
These should make using `ThinVec` feel much more like using `Vec`.
They will allow users of `Vec` to switch to `ThinVec` while continuing
to use `collect()`, `for` loops, and other parts of the iterator API.
I don't know if there were use cases before for using the iterator API
with `ThinVec`, but I would like to start using `ThinVec` in rustdoc,
and having it conform to the iterator API would make the transition
*a lot* easier.
I added a `FromIterator` impl, an `IntoIterator` impl that yields owned
elements, and `IntoIterator` impls that yield immutable or mutable
references to elements. I also added some unit tests for `ThinVec`.
Set dso_local for hidden, private and local items
This should probably have no real effect in most cases, as e.g. `hidden`
visibility already implies `dso_local` (or at least LLVM IR does not
preserve the `dso_local` setting if the item is already `hidden`), but
it should fix `-Crelocation-model=static` and improve codegen in
executables.
Note that this PR does not exhaustively port the logic in [clang], only the
portion that is necessary to fix a regression from LLVM 12 that relates to
`-Crelocation_model=static`.
Fixes#83335
[clang]: 3001d080c8/clang/lib/CodeGen/CodeGenModule.cpp (L945-L1039)
Rollup of 8 pull requests
Successful merges:
- #83370 (Add `x.py setup tools` which enables `download-rustc` by default)
- #83489 (Properly suggest deref in else block)
- #83734 (Catch a bad placeholder type error for statics in `extern`s)
- #83814 (expand: Do not ICE when a legacy AST-based macro attribute produces and empty expression)
- #83835 (rustdoc: sort search index items for compression)
- #83849 (rustdoc: Cleanup handling of associated items for intra-doc links)
- #83881 (⬆️ rust-analyzer)
- #83885 (Document compiler/ with -Aprivate-intra-doc-links)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
rustdoc: Cleanup handling of associated items for intra-doc links
Helps with https://github.com/rust-lang/rust/issues/83761 (right now the uses of the resolver are all intermingled with uses of the tyctxt). Best reviewed one commit at a time.
r? ```@bugadani``` maybe? Feel free to reassign :)
expand: Do not ICE when a legacy AST-based macro attribute produces and empty expression
Fixes https://github.com/rust-lang/rust/issues/80251
The reported error is the same as for `let _ = #[cfg(FALSE)] EXPR;`
Use tikv-jemallocator in rustc/rustdoc in addition to jemalloc-sys when enabled.
In https://github.com/rust-lang/rust/pull/81782 it was mentioned that one reason rustc may benefit from minimalloc is it doesn't use the `sdallocx` api from jemalloc.
Currently, on unix, rust uses jemalloc by importing its symbols to use them with the default, System (libc) global allocator.
This PR switches its global alloc to `tikv-jemallocator`, which correctly uses sized deallocation (https://docs.rs/tikv-jemallocator/0.4.1/src/tikv_jemallocator/lib.rs.html#121-126). `tikv-jemallocator`, as far as I can tell, is a more up-to-date set of bindings to jemalloc than `jemallocator`
The perf results of this pr are in large part due to the version upgrade of jemalloc, but sized deallocation has a non-trivial improvement, particularly to rustdoc.
This pr also includes changes to bootstrap to correctly pass the jemalloc feature through to the rustdoc build
Prevent very long compilation runtimes in LateBoundRegionNameCollector
Fixes https://github.com/rust-lang/rust/issues/83150
On recursive types such as in the example given in https://github.com/rust-lang/rust/issues/83150, the current implementation of `LateBoundRegionNameCollector` has very long compilation runtimes. To prevent those we store the types visited in the `middle::ty::Visitor` implementation of `LateBoundRegionNameCollector` in a `SsoHashSet`.
Previously, the types looked like this:
- None means this is not an associated item (but may be a variant field)
- Some(Err) means this is known to be an error. I think the only way that can happen is if it resolved and but you had your own anchor.
- Some(Ok(_, None)) was impossible.
Now, this returns a nested Option and does the error handling and
fiddling with the side channel in the caller. As a side-effect, it also
removes duplicate error handling.
This has one small change in behavior, which is that
`resolve_primitive_associated_item` now goes through `variant_field` if
it fails to resolve something. This is not ideal, but since it will be
quickly rejected anyway, I think the performance hit is worth the
cleanup.
This also fixes a bug where struct fields would forget to set the side
channel, adds a test for the bug, and ignores `private_intra_doc_links`
in rustc_resolve (since it's always documented with
--document-private-items).
Use FromStr trait for number option parsing
Replace `parse_uint` with generic `parse_number` based on `FromStr`.
Use it for parsing inlining threshold to avoid casting later.
Let `#[allow(unstable_name_collisions)]` work for things other than function
Fixes#81522
In addition to the report in #81522, currently `#[allow(unstable_name_collisions)]` doesn't suppress the corresponding diagnostics even if this attribute is appended to an expression statement or a let statement. It seems like this is because the wrong `HirId` is passed to `struct_span_lint_hir`.
It's fixed in this PR, and a regression test for it is also added.
Bump bootstrap to 1.52 beta
This includes the standard bump, but also a workaround for new cargo behavior around clearing out the doc directory when the rustdoc version changes.
Allow clobbering unsupported registers in asm!
Previously registers could only be marked as clobbered if the target feature for that register was enabled. This restriction is now removed.
cc #81092
r? ``@nagisa``
resolve/expand: Cache intermediate results of `#[derive]` expansion
Expansion function for `#[derive]` (`rustc_builtin_macros::derive::Expander::expand`) may return an indeterminate result, and therefore can be called multiple times.
Previously we parsed the `#[derive(Foo, Bar)]`'s input and tried to resolve `Foo` and `Bar` on every such call.
Now we maintain a cache `Resolver::derive_data` and take all the necessary data from it if it was computed previously.
So `Foo, Bar` is now parsed at most once, and `Foo` and `Bar` are successfully resolved at most once.
2229: Fix diagnostic issue when using FakeReads in closures
This PR fixes a diagnostic issue caused by https://github.com/rust-lang/rust/pull/82536. A temporary work around was used in this merged PR which involved feature gating the addition of FakeReads introduced as a result of pattern matching in closures.
The fix involves adding an optional closure DefId to ForLet and ForMatchedPlace FakeReadCauses. This DefId will only be added if a closure pattern matches a Place starting with an Upvar.
r? ```@nikomatsakis```
Add an unstable --json=unused-externs flag to print unused externs
This adds an unstable flag to print a list of the extern names not used by cargo.
This PR will enable cargo to collect unused dependencies from all units and provide warnings.
The companion PR to cargo is: https://github.com/rust-lang/cargo/pull/8437
The goal is eventual stabilization of this flag in rustc as well as in cargo.
Discussion of this feature is mostly contained inside these threads: #57274#72342#72603
The feature builds upon the internal datastructures added by #72342
Externs are uniquely identified by name and the information is sufficient for cargo.
If the mode is enabled, rustc will print json messages like:
```
{"unused_extern_names":["byteorder","openssl","webpki"]}
```
For a crate that got passed byteorder, openssl and webpki dependencies but needed none of them.
### Q: Why not pass -Wunused-crate-dependencies?
A: See [ehuss's comment here](https://github.com/rust-lang/rust/issues/57274#issuecomment-624839355)
TLDR: it's cleaner. Rust's warning system wasn't built to be filtered or edited by cargo.
Even a basic implementation of the feature would have to change the "n warnings emitted" line that rustc prints at the end.
Cargo ideally wants to synthesize its own warnings anyways. For example, it would be hard for rustc to emit warnings like
"dependency foo is only used by dev targets", suggesting to make it a dev-dependency instead.
### Q: Make rustc emit used or unused externs?
A: Emitting used externs has the advantage that it simplifies cargo's collection job.
However, emitting unused externs creates less data to be communicated between rustc and cargo.
Often you want to paste a cargo command obtained from `cargo build -vv` for doing something
completely unrelated. The message is emitted always, even if no warning or error is emitted.
At that point, even this tiny difference in "noise" matters. That's why I went with emitting unused externs.
### Q: One json msg per extern or a collective json msg?
A: Same as above, the data format should be concise. Having 30 lines for the 30 crates a crate uses would be disturbing to readers.
Also it helps the cargo implementation to know that there aren't more unused deps coming.
### Q: Why use names of externs instead of e.g. paths?
A: Names are both sufficient as well as neccessary to uniquely identify a passed `--extern` arg.
Names are sufficient because you *must* pass a name when passing an `--extern` arg.
Passing a path is optional on the other hand so rustc might also figure out a crate's location from the file system.
You can also put multiple paths for the same extern name, via e.g. `--extern hello=/usr/lib/hello.rmeta --extern hello=/usr/local/lib/hello.rmeta`,
but rustc will only ever use one of those paths.
Also, paths don't identify a dependency uniquely as it is possible to have multiple different extern names point to the same path.
So paths are ill-suited for identification.
### Q: What about 2015 edition crates?
A: They are fully supported.
Even on the 2015 edition, an explicit `--extern` flag is is required to enable `extern crate foo;` to work (outside of sysroot crates, which this flag doesn't warn about anyways).
So the lint would still fire on 2015 edition crates if you haven't included a dependency specified in Cargo.toml using `extern crate foo;` or similar.
The lint won't fire if your sole use in the crate is through a `extern crate foo;` statement, but that's not its job.
For detecting unused `extern crate foo` statements, there is the `unused_extern_crates` lint
which can be enabled by `#![warn(unused_extern_crates)]` or similar.
cc ```@jsgf``` ```@ehuss``` ```@petrochenkov``` ```@estebank```
Remove nightly features in rustc_type_ir
`rustc_type_ir` will be used as a type library by Chalk, which we want to be able to build on stable, so this PR removes the current nightly features used.
Add an Mmap wrapper to rustc_data_structures
This wrapper implements StableAddress and falls back to directly reading the file on wasm32.
Taken from #83640, which I will close due to the perf regression.
Translate counters from Rust 1-based to LLVM 0-based counter ids
A colleague contacted me and asked why Rust's counters start at 1, when
Clangs appear to start at 0. There is a reason why Rust's internal
counters start at 1 (see the docs), and I tried to keep them consistent
when codegenned to LLVM's coverage mapping format. LLVM should be
tolerant of missing counters, but as my colleague pointed out,
`llvm-cov` will silently fail to generate a coverage report for a
function based on LLVM's assumption that the counters are 0-based.
See:
https://github.com/llvm/llvm-project/blob/main/llvm/lib/ProfileData/Coverage/CoverageMapping.cpp#L170
Apparently, if, for example, a function has no branches, it would have
exactly 1 counter. `CounterValues.size()` would be 1, and (with the
1-based index), the counter ID would be 1. This would fail the check
and abort reporting coverage for the function.
It turns out that by correcting for this during coverage map generation,
by subtracting 1 from the Rust Counter ID (both when generating the
counter increment intrinsic call, and when adding counters to the map),
some uncovered functions (including in tests) now appear covered! This
corrects the coverage for a few tests!
r? `@tmandry`
FYI: `@wesleywiser`
