Provide suggestions for some moved value errors
When encountering an used moved value where the previous move happened
in a `match` or `if let` pattern, suggest using `ref`. Fix#63988.
When encountering a `&mut` value that is used in multiple iterations of
a loop, suggest reborrowing it with `&mut *`. Fix#62112.
Emit line info for generator variants
Debuggers should be able to read a generator / async fn state machine and show the line it's suspended at. Eventually, this could grow into an "async stack trace" feature of sorts. While no debugger support this for Rust today, this PR adds the debuginfo necessary for that support to exist.
[This gist](https://gist.github.com/tmandry/6d7004fa008684f76809208847459f9b) shows the resulting debuginfo for a simple example. Here's a snippet:
```
0x00000986: DW_TAG_variant
DW_AT_discr_value (0x03)
0x00000988: DW_TAG_member
DW_AT_name ("3")
DW_AT_type (0x000009bc "Suspend0")
DW_AT_decl_file ("/home/tmandry/code/playground/generator-simple.rs")
DW_AT_decl_line (6)
DW_AT_alignment (8)
DW_AT_data_member_location (0x00)
```
The file and line have been added here. The line currently points to the beginning of the statement containing the yield (or await), because that's what the MIR source info points to for the yield terminator. (We may want to point to the yield or await line specifically, but that can be done independently of this change.)
Debuggers don't know how to use this kind of info yet. However, we're hoping to experiment with adding such support to Fuchsia's debugger. It would be exciting if someone were interested in adding similar to support to gdb/lldb.
r? @oli-obk
cc @eddyb @jonas-schievink
Part of #73524.
Add unstable `core::mem::variant_count` intrinsic
Adds a new `const fn` intrinsic which can be used to determine the number of variants in an `enum`.
I've shown this to a couple of people and they invariably ask 'why on earth?', but there's actually a very neat use case:
At the moment, if you want to create an opaque array type that's indexed by an `enum` with one element for each variant, you either have to hard-code the number of variants, add a `LENGTH` variant or use a `Vec`, none of which are suitable in general (number of variants could change; pattern matching `LENGTH` becomes frustrating; might not have `alloc`). By including this intrinsic, it becomes possible to write the following:
```rust
#[derive(Copy, Clone)]
enum OpaqueIndex {
A = 0,
B,
C,
}
struct OpaqueVec<T>(Box<[T; std::mem::num_variants::<OpaqueIndex>()]>);
impl<T> std::ops::Index<OpaqueIndex> for OpaqueVec<T> {
type Output = T;
fn index(&self, idx: OpaqueIndex) -> &Self::Output {
&self.0[idx as usize]
}
}
```
(We even have a use cases for this in `rustc` and I plan to use it to re-implement the lang-items table.)
Implement mixed script confusable lint.
This implements the mixed script confusable lint defined in RFC 2457.
This is blocked on #72069 and https://github.com/unicode-rs/unicode-security/pull/13, and will need a Cargo.toml version bump after those are resolved.
The lint message warning is sub-optimal for now. We'll need a mechanism to properly output `AugmentScriptSet` to screen, this is to be added in `unicode-security` crate.
r? @Manishearth
When encountering an used moved value where the previous move happened
in a `match` or `if let` pattern, suggest using `ref`. Fix#63988.
When encountering a `&mut` value that is used in multiple iterations of
a loop, suggest reborrowing it with `&mut *`. Fix#62112.
Add UI test for issue 73592
It happens that #72280 accidentally fixed a bug which is later discovered in #73592. This PR adds a UI test to prevent future regression.
Closes#73592
`improper_ctypes_definitions` lint
Addresses #19834, #66220, and #66373.
This PR takes another attempt at #65134 (reverted in #66378). Instead of modifying the existing `improper_ctypes` lint to consider `extern "C" fn` definitions in addition to `extern "C" {}` declarations, this PR adds a new lint - `improper_ctypes_definitions` - which only applies to `extern "C" fn` definitions.
In addition, the `improper_ctype_definitions` lint differs from `improper_ctypes` by considering `*T` and `&T` (where `T: Sized`) FFI-safe (addressing #66220).
There wasn't a clear consensus in #66220 (where the issues with #65134 were primarily discussed) on the approach to take, but there has [been some discussion in Zulip](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/.2366220.20improper_ctypes.20definitions.20vs.20declarations/near/198903086). I fully expect that we'll want to iterate on this before landing.
cc @varkor + @shepmaster (from #19834) @hanna-kruppe (active in discussing #66220), @SimonSapin (#65134 caused problems for Servo, want to make sure that this PR doesn't)
Fixes#70718
This commit allows making associated items (e.g. associated functions
and types) into lang items via the `#[lang]` attribute. This allows such
items to be accessed directly, rather than by iterating over the parent
item's associated items.
I've added `FnOnce::Output` as a lang item, and updated one old usage to
use the new lang item. The remaining uses can be updated separately.
Add re-exports to use suggestions
In the following example, an inaccessible path is suggested via `use foo::bar::X;` whereas an accessible public exported path can be suggested instead.
```rust
mod foo {
mod bar {
pub struct X;
}
pub use self::bar::X;
}
fn main() { X; }
```
This fixes the issue.
Change heuristic for determining range literal
Currently, rustc uses a heuristic to determine if a range expression is
not a literal based on whether the expression looks like a function call
or struct initialization. This fails for range literals whose
lower/upper bounds are the results of function calls. A possibly-better
heuristic is to check if the expression contains `..`, required in range
literals.
Of course, this is also not perfect; for example, if the range
expression is a struct which includes some text with `..` this will
fail, but in general I believe it is a better heuristic.
A better alternative altogether is to add the `QPath::LangItem` enum
variant suggested in #60607. I would be happy to do this as a precursor
to this patch if someone is able to provide general suggestions on how
usages of `QPath` need to be changed later in the compiler with the
`LangItem` variant.
Closes#73553
This commit changes the improper ctypes lint (when operating on
definitions) to consider raw pointers or references to sized types as
FFI-safe.
Signed-off-by: David Wood <david@davidtw.co>
This commit adds a new lint - `improper_ctypes_definitions` - which
functions identically to `improper_ctypes`, but on `extern "C" fn`
definitions (as opposed to `improper_ctypes`'s `extern "C" {}`
declarations).
Signed-off-by: David Wood <david@davidtw.co>
Always capture tokens for `macro_rules!` arguments
When we invoke a proc-macro, the `TokenStream` we pass to it may contain 'interpolated' AST fragments, represented by `rustc_ast::token::Nonterminal`. In order to correctly, pass a `Nonterminal` to a proc-macro, we need to have 'captured' its `TokenStream` at the time the AST was parsed.
Currently, we perform this capturing when attributes are present on items and expressions, since we will end up using a `Nonterminal` to pass the item/expr to any proc-macro attributes it is annotated with. However, `Nonterminal`s are also introduced by the expansion of metavariables in `macro_rules!` macros. Since these metavariables may be passed to proc-macros, we need to have tokens available to avoid the need to pretty-print and reparse (see https://github.com/rust-lang/rust/issues/43081).
This PR unconditionally performs token capturing for AST items and expressions that are passed to a `macro_rules!` invocation. We cannot know in advance if captured item/expr will be passed to proc-macro, so this is needed to ensure that tokens will always be available when they are needed.
This ensures that proc-macros will receive tokens with proper `Spans` (both location and hygiene) in more cases. Like all work on https://github.com/rust-lang/rust/issues/43081, this will cause regressions in proc-macros that were relying on receiving tokens with dummy spans.
In this case, Crater revealed only one regression: the [Pear](https://github.com/SergioBenitez/Pear) crate (a helper for [rocket](https://github.com/SergioBenitez/Rocket)), which was previously [fixed](https://github.com/SergioBenitez/Pear/pull/25) as part of https://github.com/rust-lang/rust/pull/73084.
This regression manifests itself as the following error:
```
[INFO] [stdout] error: proc macro panicked
[INFO] [stdout] --> /opt/rustwide/cargo-home/registry/src/github.com-1ecc6299db9ec823/rocket_http-0.4.5/src/parse/uri/parser.rs:119:34
[INFO] [stdout] |
[INFO] [stdout] 119 | let path_and_query = pear_try!(path_and_query(is_pchar));
[INFO] [stdout] | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] |
[INFO] [stdout] = help: message: called `Option::unwrap()` on a `None` value
[INFO] [stdout] = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
```
It can be fixed by running `cargo update -p pear`, which updates your `Cargo.lock` to use the latest version of Pear (which includes a bugfix for the regression).
Split out from https://github.com/rust-lang/rust/pull/73084/
The const propagator cannot trace references.
Thus we avoid propagation of a local the moment we encounter references to it.
fixes#73609
cc @RalfJung
r? @wesleywiser
Point at the call span when overflow occurs during monomorphization
This improves the output for issue #72577, but there's still more work
to be done.
Currently, an overflow error during monomorphization results in an error
that points at the function we were unable to monomorphize. However, we
don't point at the call that caused the monomorphization to happen. In
the overflow occurs in a large recursive function, it may be difficult
to determine where the issue is.
This commit tracks and `Span` information during collection of
`MonoItem`s, which is used when emitting an overflow error. `MonoItem`
itself is unchanged, so this only affects
`src/librustc_mir/monomorphize/collector.rs`
rustdoc: Fix doc aliases with crate filtering
Fix a crash when searching for an alias contained in the currently selected filter crate.
Also remove alias search results for crates that should be filtered out.
The test suite needed to be fixed to actually take into account the crate filtering and check that there are no results when none are expected.
Needs to be backported to beta to fix the `std` docs.
Fixes#73620
r? @GuillaumeGomez
In the following example, an inaccessible path is suggested via
`use foo::bar::X;` whereas an accessible public exported path can
be suggested instead.
```
mod foo {
mod bar {
pub struct X;
}
pub use self::bar::X;
}
fn main() { X; }
```
This fixes the issue.
Fix a crash when searching for an alias contained in the currently selected filter crate.
Also remove alias search results for crates that should be filtered out.
The test suite needed to be fixed to actually take into account the crate filtering and check that there are no results when none are expected.
Add second message for LiveDrop errors
This is an attempt to fix https://github.com/rust-lang/rust/issues/72907 by adding a second message to the `LiveDrop` diagnostics. Changing from this
```
error[E0493]: destructors cannot be evaluated at compile-time
--> src/lib.rs:7:9
|
7 | let mut always_returned = None;
| ^^^^^^^^^^^^^^^^^^^ constants cannot evaluate destructors
error: aborting due to previous error
```
to this
```
error[E0493]: destructors cannot be evaluated at compile-time
--> foo.rs:6:9
|
6 | let mut always_returned = None;
| ^^^^^^^^^^^^^^^^^^^ constants cannot evaluate destructors
...
10 | always_returned = never_returned;
| --------------- value is dropped here
error: aborting due to previous error
```
r? @RalfJung @ecstatic-morse
Account for multiple impl/dyn Trait in return type when suggesting `'_`
Make `impl` and `dyn` Trait lifetime suggestions a bit more resilient.
Follow up to #72804.
r? @nikomatsakis
move leak-check to during coherence, candidate eval
Implementation of MCP https://github.com/rust-lang/compiler-team/issues/295.
I'd like to do a crater run on this.
Note to @rust-lang/lang: This PR is a breaking change (bugfix). It causes tests like the following to go from a future-compatibility warning #56105 to a hard error:
```rust
trait Trait {}
impl Trait for for<'a, 'b> fn(&'a u32, &'b u32) {}
impl Trait for for<'c> fn(&'c u32, &'c u32) {} // now rejected, used to warn
```
I am not aware of any instances of this code in the wild, but that is why we are doing a crater run. The reason for this change is that those two types are, in fact, the same type, and hence the two impls are overlapping.
There will still be impls that trigger #56105 after this lands, however -- I hope that we will eventually just accept those impls without warning, for the most part. One example of such an impl is this pattern, which is used by wasm-bindgen and other crates as well:
```rust
trait Trait {}
impl<T> Trait for fn(&T) { }
impl<T> Trait for fn(T) { } // still accepted, but warns
```
Improve compiler error message for wrong generic parameter order
- Added optional "help" parameter that shows a help message on the compiler error if required.
- Added a simple ordered parameter as a sample help.
@varkor will make more changes as required. Let me know if I'm heading in the right direction.
Fixes#68437
r? @varkor
Currently, rustc uses a heuristic to determine if a range expression is
not a literal based on whether the expression looks like a function call
or struct initialization. This fails for range literals whose
lower/upper bounds are the results of function calls. A possibly-better
heuristic is to check if the expression contains `..`, required in range
literals.
Of course, this is also not perfect; for example, if the range
expression is a struct which includes some text with `..` this will
fail, but in general I believe it is a better heuristic.
A better alternative altogether is to add the `QPath::LangItem` enum
variant suggested in #60607. I would be happy to do this as a precursor
to this patch if someone is able to provide general suggestions on how
usages of `QPath` need to be changed later in the compiler with the
`LangItem` variant.
Closes#73553
Fix spurious 'value moved here in previous iteration of loop' messages
Fixes#46099
Previously, we would check the 'move' and 'use' spans to see if we
should emit this message. However, this can give false positives when
macros are involved, since two distinct expressions may end up with the
same span.
Instead, we check the actual MIR `Location`, which eliminates false
positives.
