- Closures in external crates may get compiled in because of
monomorphization. We should store names of captured variables
in `optimized_mir`, so that they are written into the metadata
file and we can use them to generate debuginfo.
- If there are breakpoints inside closures, the names of captured
variables stored in `optimized_mir` can be used to print them.
Now the name is more precise when disjoint fields are captured.
Check whether the closure's owner is an ADT in thir-unsafeck
This pull request fixes#85871. The code in `rustc_mir_build/src/check_unsafety.rs` incorrectly assumes that a closure's owner always has a body, but only functions, closures, and constants have bodies, whereas a closure can also appear inside a struct or enum:
```rust
struct S {
arr: [(); match || 1 { _ => 42 }]
}
enum E {
A([(); { || 1; 42 }])
}
```
This pull request fixes the resulting ICE by checking whether the closure's owner is an ADT and only deferring to `thir_check_unsafety(owner)` if it isn't.
Fix `unused_unsafe` around `await`
Enables `unused_unsafe` lint for `unsafe { future.await }`.
The existing test for this is `unsafe { println!() }`, so I assume that `println!` used to contain compiler-generated unsafe but this is no longer true, and so the existing test is broken. I replaced the test with `unsafe { ...await }`. I believe `await` is currently the only instance of compiler-generated unsafe.
Reverts some parts of #85421, but the issue predates that PR.
Add pattern walking support to THIR walker
Suggested in https://github.com/rust-lang/rust/pull/85263#issuecomment-861906730, this splits off the support for pattern walking in THIR from #85263. This has no observable effect on THIR unsafety checking, since it is not currently possible to trigger unsafety from the THIR checker using the additional patterns or constants that are now walked. THIR patterns are walked in source code order.
r? `@LeSeulArtichaut`
Remove some last remants of {push,pop}_unsafe!
These macros have already been removed, but there was still some code handling these macros. That code is now removed.
Remove unused feature gates
The first commit removes a usage of a feature gate, but I don't expect it to be controversial as the feature gate was only used to workaround a limitation of rust in the past. (closures never being `Clone`)
The second commit uses `#[allow_internal_unstable]` to avoid leaking the `trusted_step` feature gate usage from inside the index newtype macro. It didn't work for the `min_specialization` feature gate though.
The third commit removes (almost) all feature gates from the compiler that weren't used anyway.
rustc: Allow safe #[target_feature] on wasm
This commit updates the compiler's handling of the `#[target_feature]`
attribute when applied to functions on WebAssembly-based targets. The
compiler in general requires that any functions with `#[target_feature]`
are marked as `unsafe` as well, but this commit relaxes the restriction
for WebAssembly targets where the attribute can be applied to safe
functions as well.
The reason this is done is that the motivation for this feature of the
compiler is not applicable for WebAssembly targets. In general the
`#[target_feature]` attribute is used to enhance target CPU features
enabled beyond the basic level for the rest of the compilation. If done
improperly this means that your program could execute an instruction
that the CPU you happen to be running on does not understand. This is
considered undefined behavior where it is unknown what will happen (e.g.
it's not a deterministic `SIGILL`).
For WebAssembly, however, the target is different. It is not possible
for a running WebAssembly program to execute an instruction that the
engine does not understand. If this were the case then the program would
not have validated in the first place and would not run at all. Even if
this were allowed in some hypothetical future where engines have some
form of runtime feature detection (which they do not right now) any
implementation of such a feature would generate a trap if a module
attempts to execute an instruction the module does not understand. This
deterministic trap behavior would still not fall into the category of
undefined behavior because the trap is deterministic.
For these reasons the `#[target_feature]` attribute is now allowed on
safe functions, but only for WebAssembly targets. This notably enables
the wasm-SIMD intrinsics proposed for stabilization in #74372 to be
marked as safe generally instead of today where they're all `unsafe` due
to the historical implementation of `#[target_feature]` in the compiler.
Make `Step` trait safe to implement
This PR makes a few modifications to the `Step` trait that I believe better position it for stabilization in the short term. In particular,
1. `unsafe trait TrustedStep` is introduced, indicating that the implementation of `Step` for a given type upholds all stated invariants (which have remained unchanged). This is gated behind a new `trusted_step` feature, as stabilization is realistically blocked on min_specialization.
2. The `Step` trait is internally specialized on the `TrustedStep` trait, which avoids a serious performance regression.
3. `TrustedLen` is implemented for `T: TrustedStep` as the latter's invariants subsume the former's.
4. The `Step` trait is no longer `unsafe`, as the invariants must not be relied upon by unsafe code (unless the type implements `TrustedStep`).
5. `TrustedStep` is implemented for all types that implement `Step` in the standard library and compiler.
6. The `step_trait_ext` feature is merged into the `step_trait` feature. I was unable to find any reasoning for the features being split; the `_unchecked` methods need not necessarily be stabilized at the same time, but I think it is useful to have them under the same feature flag.
All existing implementations of `Step` will be broken, as it is not possible to `unsafe impl` a safe trait. Given this trait only exists on nightly, I feel this breakage is acceptable. The blanket `impl<T: Step> TrustedLen for T` will likely cause some minor breakage, but this should be covered by the equivalent impl for `TrustedStep`.
Hopefully these changes are sufficient to place `Step` in decent position for stabilization, which would allow user-defined types to be used with `a..b` syntax.
This commit updates the compiler's handling of the `#[target_feature]`
attribute when applied to functions on WebAssembly-based targets. The
compiler in general requires that any functions with `#[target_feature]`
are marked as `unsafe` as well, but this commit relaxes the restriction
for WebAssembly targets where the attribute can be applied to safe
functions as well.
The reason this is done is that the motivation for this feature of the
compiler is not applicable for WebAssembly targets. In general the
`#[target_feature]` attribute is used to enhance target CPU features
enabled beyond the basic level for the rest of the compilation. If done
improperly this means that your program could execute an instruction
that the CPU you happen to be running on does not understand. This is
considered undefined behavior where it is unknown what will happen (e.g.
it's not a deterministic `SIGILL`).
For WebAssembly, however, the target is different. It is not possible
for a running WebAssembly program to execute an instruction that the
engine does not understand. If this were the case then the program would
not have validated in the first place and would not run at all. Even if
this were allowed in some hypothetical future where engines have some
form of runtime feature detection (which they do not right now) any
implementation of such a feature would generate a trap if a module
attempts to execute an instruction the module does not understand. This
deterministic trap behavior would still not fall into the category of
undefined behavior because the trap is deterministic.
For these reasons the `#[target_feature]` attribute is now allowed on
safe functions, but only for WebAssembly targets. This notably enables
the wasm-SIMD intrinsics proposed for stabilization in #74372 to be
marked as safe generally instead of today where they're all `unsafe` due
to the historical implementation of `#[target_feature]` in the compiler.
readd capture disjoint fields gate
This readds a feature gate guard that was added in PR #83521. (Basically, there were unintended consequences to the code exposed by removing the feature gate guard.)
The root bug still remains to be resolved, as discussed in issue #85561. This is just a band-aid suitable for a beta backport.
Cc issue #85435
Note that the latter issue is unfixed until we backport this (or another fix) to 1.53 beta
Bump bootstrap compiler to beta 1.53.0
This PR bumps the bootstrap compiler to version 1.53.0 beta, as part of our usual release process (this was supposed to be Wednesday's step, but creating the beta release took longer than expected).
The PR also includes the "Bootstrap: skip rustdoc fingerprint for building docs" commit, see the reasoning [on Zulip](https://zulip-archive.rust-lang.org/241545trelease/88450153betabootstrap.html).
r? `@Mark-Simulacrum`
Make building THIR a stealable query
This PR creates a stealable `thir_body` query so that we can build the THIR only once for THIR unsafeck and MIR build.
Blocked on #83842.
r? `@nikomatsakis`
Improve error message for non-exhaustive matches on non-exhaustive enums
This pull request fixes#85227. For an enum marked with `#[non_exhaustive]` and not defined in the current crate, the error message for non-exhaustive matches now mentions the fact that the enum is marked as non-exhaustive:
```
error[E0004]: non-exhaustive patterns: `_` not covered
--> main.rs:12:11
|
12 | match e {
| ^ pattern `_` not covered
|
= help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
= note: the matched value is of type `E`, which is marked as non-exhaustive
```
Store VariantIdx to distinguish enum variants
This saves ~24% of the instructions on the match-stress-enum benchmark, but I'm not 100% sure that this is OK - if we ever compare two constructors across enums (e.g., a Result and an Option), then this is obviously insufficient; I can experiment with continuing to store the DefId for comparison purposes in that case.
further split up const_fn feature flag
This continues the work on splitting up `const_fn` into separate feature flags:
* `const_fn_trait_bound` for `const fn` with trait bounds
* `const_fn_unsize` for unsizing coercions in `const fn` (looks like only `dyn` unsizing is still guarded here)
I don't know if there are even any things left that `const_fn` guards... at least libcore and liballoc do not need it any more.
`@oli-obk` are you currently able to do reviews?
Add coverage to continue statements
`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.
r? `@tmandry`
cc: `@wesleywiser`
`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.
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.
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.
normalize mir::Constant differently from ty::Const in preparation for valtrees
Valtrees are unable to represent many kind of constant values (this is on purpose). For constants that are used at runtime, we do not need a valtree representation and can thus use a different form of evaluation. In order to make this explicit and less fragile, I added a `fold_constant` method to `TypeFolder` and implemented it for normalization. Normalization can now, when it wants to eagerly evaluate a constant, normalize `mir::Constant` directly into a `mir::ConstantKind::Val` instead of relying on the `ty::Const` evaluation.
In the future we can get rid of the `ty::Const` in there entirely and add our own `Unevaluated` variant to `mir::ConstantKind`. This would allow us to remove the `promoted` field from `ty::ConstKind::Unevaluated`, as promoteds can never occur in the type system.
cc `@rust-lang/wg-const-eval`
r? `@lcnr`
make changes to liveness to use closure_min_captures
use different span
borrow check uses new structures
rename to CapturedPlace
stop using upvar_capture in regionck
remove the bridge
cleanup from rebase + remove the upvar_capture reference from mutability_errors.rs
remove line from livenes test
make our unused var checking more consistent
update tests
adding more warnings to the tests
move is_ancestor_or_same_capture to rustc_middle/ty
update names to reflect the closures
add FIXME
check that all captures are immutable borrows before returning
add surrounding if statement like the original
move var out of the loop and rename
Co-authored-by: Logan Mosier <logmosier@gmail.com>
Co-authored-by: Roxane Fruytier <roxane.fruytier@hotmail.com>
ast/hir: Rename field-related structures
I always forget what `ast::Field` and `ast::StructField` mean despite working with AST for long time, so this PR changes the naming to less confusing and more consistent.
- `StructField` -> `FieldDef` ("field definition")
- `Field` -> `ExprField` ("expression field", not "field expression")
- `FieldPat` -> `PatField` ("pattern field", not "field pattern")
Various visiting and other methods working with the fields are renamed correspondingly too.
The second commit reduces the size of `ExprKind` by boxing fields of `ExprKind::Struct` in preparation for https://github.com/rust-lang/rust/pull/80080.
Implement (but don't use) valtree and refactor in preparation of use
This PR does not cause any functional change. It refactors various things that are needed to make valtrees possible. This refactoring got big enough that I decided I'd want it reviewed as a PR instead of trying to make one huge PR with all the changes.
cc `@rust-lang/wg-const-eval` on the following commits:
* 2027184 implement valtree
* eeecea9 fallible Scalar -> ScalarInt
* 042f663 ScalarInt convenience methods
cc `@eddyb` on ef04a6d
cc `@rust-lang/wg-mir-opt` for cf1700c (`mir::Constant` can now represent either a `ConstValue` or a `ty::Const`, and it is totally possible to have two different representations for the same value)
2229: Handle patterns within closures correctly when `capture_disjoint_fields` is enabled
This PR fixes several issues related to handling patterns within closures when `capture_disjoint_fields` is enabled.
1. Matching is always considered a use of the place, even with `_` patterns
2. Compiler ICE when capturing fields in closures through `let` assignments
To do so, we
- Introduced new Fake Reads
- Delayed use of `Place` in favor of `PlaceBuilder`
- Ensured that `PlaceBuilder` can be resolved before attempting to extract `Place` in any of the pattern matching code
Closes rust-lang/project-rfc-2229/issues/27
Closes rust-lang/project-rfc-2229/issues/24
r? `@nikomatsakis`
StructField -> FieldDef ("field definition")
Field -> ExprField ("expression field", not "field expression")
FieldPat -> PatField ("pattern field", not "field pattern")
Also rename visiting and other methods working on them.
Eagerly construct bodies of THIR
With this PR:
- the THIR is no longer constructed lazily, but is entirely built before being passed to the MIR Builder
- the THIR is now allocated in arenas instead of `Box`es
However, this PR doesn't make any changes to the way patterns are constructed: they are still boxed, and exhaustiveness checking is unchanged.
Implements MCP rust-lang/compiler-team#409.
Closesrust-lang/project-thir-unsafeck#1.
r? `@ghost` cc `@nikomatsakis` `@oli-obk`
Implement RFC 2945: "C-unwind" ABI
## Implement RFC 2945: "C-unwind" ABI
This branch implements [RFC 2945]. The tracking issue for this RFC is #74990.
The feature gate for the issue is `#![feature(c_unwind)]`.
This RFC was created as part of the ffi-unwind project group tracked at rust-lang/lang-team#19.
### Changes
Further details will be provided in commit messages, but a high-level overview
of the changes follows:
* A boolean `unwind` payload is added to the `C`, `System`, `Stdcall`,
and `Thiscall` variants, marking whether unwinding across FFI boundaries is
acceptable. The cases where each of these variants' `unwind` member is true
correspond with the `C-unwind`, `system-unwind`, `stdcall-unwind`, and
`thiscall-unwind` ABI strings introduced in RFC 2945 [3].
* This commit adds a `c_unwind` feature gate for the new ABI strings.
Tests for this feature gate are included in `src/test/ui/c-unwind/`, which
ensure that this feature gate works correctly for each of the new ABIs.
A new language features entry in the unstable book is added as well.
* We adjust the `rustc_middle::ty::layout::fn_can_unwind` function,
used to compute whether or not a `FnAbi` object represents a function that
should be able to unwind when `panic=unwind` is in use.
* Changes are also made to
`rustc_mir_build::build::should_abort_on_panic` so that the function ABI is
used to determind whether it should abort, assuming that the `panic=unwind`
strategy is being used, and no explicit unwind attribute was provided.
[RFC 2945]: https://github.com/rust-lang/rfcs/blob/master/text/2945-c-unwind-abi.md
### Add debug assertion to check `AbiDatas` ordering
This makes a small alteration to `Abi::index`, so that we include a
debug assertion to check that the index we are returning corresponds
with the same abi in our data array.
This will help prevent ordering bugs in the future, which can
manifest in rather strange errors.
### Using exhaustive ABI matches
This slightly modifies the changes from our previous commits,
favoring exhaustive matches in place of `_ => ...` fall-through
arms.
This should help with maintenance in the future, when additional
ABI's are added, or when existing ABI's are modified.
### List all `-unwind` ABI's in unstable book
This updates the `c-unwind` page in the unstable book to list _all_
of the other ABI strings that are introduced by this feature gate.
Now, all of the ABI's specified by RFC 2945 are shown.
Co-authored-by: Amanieu d'Antras <amanieu@gmail.com>
Co-authored-by: Niko Matsakis <niko@alum.mit.edu>
### Changes
This commit implements unwind ABI's, specified in RFC 2945.
We adjust the `rustc_middle::ty::layout::fn_can_unwind` function,
used to compute whether or not a `FnAbi` object represents a
function that should be able to unwind when `panic=unwind` is in
use.
Changes are also made to
`rustc_mir_build::build::should_abort_on_panic` so that the
function ABI is used to determind whether it should abort, assuming
that the `panic=unwind` strategy is being used, and no explicit
unwind attribute was provided.
### Tests
Unit tests, checking that the behavior is correct for `C-unwind`,
`stdcall-unwind`, `system-unwind`, and `thiscall-unwind`, are
included. These alternative `unwind` ABI strings are specified in
RFC 2945, in the "_Other `unwind` ABI strings_" section.
Additionally, a test case is included to assert that the LLVM IR
generated for an external function defined with the `C-unwind` ABI
will be appropriately labeled with the `nounwind` LLVM attribute
when the `panic=abort` compilation flag is used.
### Ignore Directives
This commit uses `ignore-*` directives in two of our `*-unwind` ABI
test cases.
Specifically, the `stdcall-unwind` and `thiscall-unwind` test cases
ignore architectures that do not support `stdcall` and `thiscall`,
respectively.
These directives are cribbed from
`src/test/ui/c-variadic/variadic-ffi-1.rs` for `stdcall`, and
`src/test/ui/extern/extern-thiscall.rs` for `thiscall`.
Change x64 size checks to not apply to x32.
Rust contains various size checks conditional on target_arch = "x86_64", but these checks were never intended to apply to x86_64-unknown-linux-gnux32. Add target_pointer_width = "64" to the conditions.
Rust contains various size checks conditional on target_arch = "x86_64",
but these checks were never intended to apply to
x86_64-unknown-linux-gnux32. Add target_pointer_width = "64" to the
conditions.
Implement NOOP_METHOD_CALL lint
Implements the beginnings of https://github.com/rust-lang/lang-team/issues/67 - a lint for detecting noop method calls (e.g, calling `<&T as Clone>::clone()` when `T: !Clone`).
This PR does not fully realize the vision and has a few limitations that need to be addressed either before merging or in subsequent PRs:
* [ ] No UFCS support
* [ ] The warning message is pretty plain
* [ ] Doesn't work for `ToOwned`
The implementation uses [`Instance::resolve`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/instance/struct.Instance.html#method.resolve) which is normally later in the compiler. It seems that there are some invariants that this function relies on that we try our best to respect. For instance, it expects substitutions to have happened, which haven't yet performed, but we check first for `needs_subst` to ensure we're dealing with a monomorphic type.
Thank you to ```@davidtwco,``` ```@Aaron1011,``` and ```@wesleywiser``` for helping me at various points through out this PR ❤️.
Inline hot part of PatStack::head_ctor
When building rustc with `-Codegen-units=1` this inline hint ensures
that obtaining already initialized head constructor does not involve
a function call overhead and reduces the instruction count in
match-stress-enum-check full benchmark from 11.9G to 9.8G.
It shouldn't have significant impact on the currently default
configuration where it reflects existing inlining decisions.
Replace if-let and while-let with `if let` and `while let`
This pull request replaces if-let and while-let with `if let` and `while let`.
closes https://github.com/rust-lang/rust/issues/82205
When building rustc with `-Codegen-units=1` this inline hint ensures
that obtaining already initialized head constructor does not involve
a function call overhead and reduces the instruction count in
match-stress-enum-check full benchmark from 11.9G to 9.8G.
It shouldn't have significant impact on the currently default
configuration where it reflects existing inlining decisions.
The `rustc_data_structures::sync::OnceCell` is thread-safe when building
a parallel compiler. This is unnecessary for the purposes of pattern
usefulness checking. Use `!Sync` `std::lazy::OnceCell` instead.
Use debug log level for developer oriented logs
The information logged here is of limited general interest, while at the
same times makes it impractical to simply enable logging and share the
resulting logs due to the amount of the output produced.
Reduce log level from info to debug for developer oriented information.
For example, when building cargo, this reduces the amount of logs
generated by `RUSTC_LOG=info cargo build` from 265 MB to 79 MB.
Continuation of changes from 81350.
The information logged here is of limited general interest, while at the
same times makes it impractical to simply enable logging and share the
resulting logs due to the amount of the output produced.
Reduce log level from info to debug for developer oriented information.
For example, when building cargo, this reduces the amount of logs
generated by `RUSTC_LOG=info cargo build` from 265 MB to 79 MB.
Continuation of changes from 81350.
Reduce log level used by tracing instrumentation from info to debug
Restore log level to debug to avoid make info log level overly verbose (the uses of instrument attribute modified there, were for the most part a replacement for `debug!`; one use was novel).
This renames the variants in HIR UnOp from
enum UnOp {
UnDeref,
UnNot,
UnNeg,
}
to
enum UnOp {
Deref,
Not,
Neg,
}
Motivations:
- This is more consistent with the rest of the code base where most enum
variants don't have a prefix.
- These variants are never used without the `UnOp` prefix so the extra
`Un` prefix doesn't help with readability. E.g. we don't have any
`UnDeref`s in the code, we only have `UnOp::UnDeref`.
- MIR `UnOp` type variants don't have a prefix so this is more
consistent with MIR types.
- "un" prefix reads like "inverse" or "reverse", so as a beginner in
rustc code base when I see "UnDeref" what comes to my mind is
something like "&*" instead of just "*".
Identify unreachable subpatterns more reliably
In https://github.com/rust-lang/rust/pull/80104 I used `Span`s to identify unreachable sub-patterns in the presence of or-patterns during exhaustiveness checking. In https://github.com/rust-lang/rust/issues/80501 it was revealed that `Span`s are complicated and that this was not a good idea.
Instead, this PR identifies subpatterns logically: as a path in the tree of subpatterns of a given pattern. I made a struct that captures a set of such subpatterns. This is a bit complex, but thankfully self-contained; the rest of the code does not need to know anything about it.
Fixes https://github.com/rust-lang/rust/issues/80501. I think I managed to keep the perf neutral.
r? `@varkor`
2229: Fix issues with move closures and mutability
This PR fixes two issues when feature `capture_disjoint_fields` is used.
1. Can't mutate using a mutable reference
2. Move closures try to move value out through a reference.
To do so, we
1. Compute the mutability of the capture and store it as part of the `CapturedPlace` that is written in TypeckResults
2. Restrict capture precision. Note this is temporary for now, to allow the feature to be used with move closures and ByValue captures and might change depending on discussions with the lang team.
- No Derefs are captured for ByValue captures, since that will result in value behind a reference getting moved.
- No projections are applied to raw pointers since these require unsafe blocks. We capture
them completely.
r? `````@nikomatsakis`````
Support FRU pattern with `[feature(capture_disjoint_fields)]`
In case of a functional record update syntax for creating a structure, `ExprUseVisitor` to only detect the precise use of some of the field in the `..x` part of the syntax. However, when we start building MIR, we
1. First, build the place for `x`
2. and then, add precise field projections so that only some parts of `x` end up getting read.
When `capture_disjoint_fields` is enabled, and FRU is used within a closure `x` won't be completely captured, and therefore the first step will fail. This PR updates `mir_build` to create a place builder in the first step and then create place from the builder only after applying the field projection.
Closes https://github.com/rust-lang/project-rfc-2229/issues/32
r? ``````@nikomatsakis``````
