rustc: Fill out remaining parts of C-unwind ABI
This commit intends to fill out some of the remaining pieces of the
C-unwind ABI. This has a number of other changes with it though to move
this design space forward a bit. Notably contained within here is:
* On `panic=unwind`, the `extern "C"` ABI is now considered as "may
unwind". This fixes a longstanding soundness issue where if you
`panic!()` in an `extern "C"` function defined in Rust that's actually
UB because the LLVM representation for the function has the `nounwind`
attribute, but then you unwind.
* Whether or not a function unwinds now mainly considers the ABI of the
function instead of first checking the panic strategy. This fixes a
miscompile of `extern "C-unwind"` with `panic=abort` because that ABI
can still unwind.
* The aborting stub for non-unwinding ABIs with `panic=unwind` has been
reimplemented. Previously this was done as a small tweak during MIR
generation, but this has been moved to a separate and dedicated MIR
pass. This new pass will, for appropriate functions and function
calls, insert a `cleanup` landing pad for any function call that may
unwind within a function that is itself not allowed to unwind. Note
that this subtly changes some behavior from before where previously on
an unwind which was caught-to-abort it would run active destructors in
the function, and now it simply immediately aborts the process.
* The `#[unwind]` attribute has been removed and all users in tests and
such are now using `C-unwind` and `#![feature(c_unwind)]`.
I think this is largely the last piece of the RFC to implement.
Unfortunately I believe this is still not stabilizable as-is because
activating the feature gate changes the behavior of the existing `extern
"C"` ABI in a way that has no replacement. My thinking for how to enable
this is that we add support for the `C-unwind` ABI on stable Rust first,
and then after it hits stable we change the behavior of the `C` ABI.
That way anyone straddling stable/beta/nightly can switch to `C-unwind`
safely.
rustc: Replace `HirId`s with `LocalDefId`s in `AccessLevels` tables
and passes using those tables - primarily privacy checking, stability checking and dead code checking.
All these passes work with definitions rather than with arbitrary HIR nodes.
r? `@cjgillot`
cc `@lambinoo` (#87487)
Trait upcasting coercion (part2)
This is the second part of trait upcasting coercion implementation.
Currently this is blocked on #86264 .
The third part might be implemented using unsafety checking
r? `@bjorn3`
This commit intends to fill out some of the remaining pieces of the
C-unwind ABI. This has a number of other changes with it though to move
this design space forward a bit. Notably contained within here is:
* On `panic=unwind`, the `extern "C"` ABI is now considered as "may
unwind". This fixes a longstanding soundness issue where if you
`panic!()` in an `extern "C"` function defined in Rust that's actually
UB because the LLVM representation for the function has the `nounwind`
attribute, but then you unwind.
* Whether or not a function unwinds now mainly considers the ABI of the
function instead of first checking the panic strategy. This fixes a
miscompile of `extern "C-unwind"` with `panic=abort` because that ABI
can still unwind.
* The aborting stub for non-unwinding ABIs with `panic=unwind` has been
reimplemented. Previously this was done as a small tweak during MIR
generation, but this has been moved to a separate and dedicated MIR
pass. This new pass will, for appropriate functions and function
calls, insert a `cleanup` landing pad for any function call that may
unwind within a function that is itself not allowed to unwind. Note
that this subtly changes some behavior from before where previously on
an unwind which was caught-to-abort it would run active destructors in
the function, and now it simply immediately aborts the process.
* The `#[unwind]` attribute has been removed and all users in tests and
such are now using `C-unwind` and `#![feature(c_unwind)]`.
I think this is largely the last piece of the RFC to implement.
Unfortunately I believe this is still not stabilizable as-is because
activating the feature gate changes the behavior of the existing `extern
"C"` ABI in a way that has no replacement. My thinking for how to enable
this is that we add support for the `C-unwind` ABI on stable Rust first,
and then after it hits stable we change the behavior of the `C` ABI.
That way anyone straddling stable/beta/nightly can switch to `C-unwind`
safely.
CTFE: throw unsupported error when partially overwriting a pointer
Currently, during CTFE, when a write to memory would overwrite parts of a pointer, we make the remaining parts of that pointer "uninitialized". This is probably not what users expect, so if this ever happens they will be quite confused about why some of the data just vanishes for seemingly no good reason.
So I propose we change this to abort CTFE when that happens, to at last avoid silently doing the wrong thing.
Cc https://github.com/rust-lang/rust/issues/87184
Our CTFE test suite still seems to pass. However, we should probably crater this, and I want to do some tests with Miri as well.
rfc3052 followup: Remove authors field from Cargo manifests
Since RFC 3052 soft deprecated the authors field, hiding it from
crates.io, docs.rs, and making Cargo not add it by default, and it is
not generally up to date/useful information for contributors, we may as well
remove it from crates in this repo.
Bail on any found recursion when expanding opaque types
Fixes#87450. More of a bandaid because it does not fix the exponential complexity of the type folding used for opaque type expansion.
Since RFC 3052 soft deprecated the authors field anyway, hiding it from
crates.io, docs.rs, and making Cargo not add it by default, and it is
not generally up to date/useful information, we should remove it from
crates in this repo.
Support -Z unpretty=thir-tree again
Currently `-Z unpretty=thir-tree` is broken after some THIR refactorings. This re-implements it, making it easier to debug THIR-related issues.
We have to do analyzes before getting the THIR, since trying to create THIR from invalid HIR can ICE. But doing those analyzes requires the THIR to be built and stolen. We work around this by creating a separate query to construct the THIR tree string representation.
Closes https://github.com/rust-lang/project-thir-unsafeck/issues/8, fixes#85552.
get rid of NoMirFor error variant
The only place where we throw that error, it is very quickly caught again and turned into a different error. So raise that other error immediately.
Add flag to configure `large_assignments` lint
The `large_assignments` lints detects moves over specified limit. The
limit is configured through `move_size_limit = "N"` attribute placed at
the root of a crate. When attribute is absent, the lint is disabled.
Make it possible to enable the lint without making any changes to the
source code, through a new flag `-Zmove-size-limit=N`. For example, to
detect moves exceeding 1023 bytes in a cargo crate, including all
dependencies one could use:
```
$ env RUSTFLAGS=-Zmove-size-limit=1024 cargo build -vv
```
Lint tracking issue #83518.
Store all HIR owners in the same container
This replaces the previous storage in a BTreeMap for each of Item/ImplItem/TraitItem/ForeignItem.
This should allow for a more compact storage.
Based on https://github.com/rust-lang/rust/pull/83114
dont provide fwd declared params to cg defaults
Fixes#83938
```rust
#![feature(const_evaluatable_checked, const_generics, const_generics_defaults)]
#![allow(incomplete_features)]
pub struct Bar<const N: usize, const M: usize = { N + 1 }>;
pub fn foo<const N1: usize>() -> Bar<N1> { loop {} }
fn main() {}
```
This PR makes this code no longer ICE, it was ICE'ing previously because when building substs for `Bar<N1>` we would subst the anon ct: `ConstKind::Unevaluated({N + 1}, substs: [N, M])` with substs of `[N1]`. the anon const has forward declared params supplied though so we end up trying to substitute the provided `M` param which causes the ICE.
This PR doesn't handle the predicates of the const so
```rust
trait Foo<const N: usize> { const Assoc: usize; }
pub struct Bar<const N: usize = { <()>::Assoc }> where (): Foo<N>;
```
Resolves to `<() as Foo<N>>::Assoc` which can allow for using fwd declared params indirectly.
```rust
trait Foo<const N: usize> {}
struct Bar<const N: usize = { 2 + 3 }> where (): Foo<N>;
```
This code also ICEs under this PR because instantiating the default's predicates causes an ICE as predicates_of contains predicates with fwd declared params
PR was briefly discussed [in this zulip thread](https://rust-lang.zulipchat.com/#narrow/stream/260443-project-const-generics/topic/evil.20preds.20in.20param.20env.20.2386580)
Fix span when suggesting to add an associated type bound
Fixes#87261
Note that this fix is not perfect, it ~~will still give incorrect~~ won't give suggestions in some situations:
- If the associated type is defined on a supertrait of those contained in the opaque type, it will fallback to the previous behaviour, e.g. if `AssocTy` is defined on the trait `Foo`, `Bar` has `Foo` as supertrait and the opaque type is a `impl Bar + Baz`.
- If the the associated type is defined on a generic trait and the opaque type includes two versions of that generic trait, e.g. the opaque type is `impl Foo<A> + Foo<B>`
Refactor vtable format for upcoming trait_upcasting feature.
This modifies vtable format:
1. reordering occurrence order of methods coming from different traits
2. include `VPtr`s for supertraits where this vtable cannot be directly reused during trait upcasting.
Also, during codegen, the vtables corresponding to these newly included `VPtr` will be requested and generated.
For the cases where this vtable can directly used, now the super trait vtable has exactly the same content to some prefix of this one.
r? `@bjorn3`
cc `@RalfJung`
cc `@rust-lang/wg-traits`
Support HIR wf checking for function signatures
During function type-checking, we normalize any associated types in
the function signature (argument types + return type), and then
create WF obligations for each of the normalized types. The HIR wf code
does not currently support this case, so any errors that we get have
imprecise spans.
This commit extends `ObligationCauseCode::WellFormed` to support
recording a function parameter, allowing us to get the corresponding
HIR type if an error occurs. Function typechecking is modified to
pass this information during signature normalization and WF checking.
The resulting code is fairly verbose, due to the fact that we can
no longer normalize the entire signature with a single function call.
As part of the refactoring, we now perform HIR-based WF checking
for several other 'typed items' (statics, consts, and inherent impls).
As a result, WF and projection errors in a function signature now
have a precise span, which points directly at the responsible type.
If a function signature is constructed via a macro, this will allow
the error message to point at the code 'most responsible' for the error
(e.g. a user-supplied macro argument).
When pretty printing, name placeholders as bound regions
Split from #85499
When we see a placeholder that we are going to print, treat it as a bound var (and add it to a `for<...>`
During function type-checking, we normalize any associated types in
the function signature (argument types + return type), and then
create WF obligations for each of the normalized types. The HIR wf code
does not currently support this case, so any errors that we get have
imprecise spans.
This commit extends `ObligationCauseCode::WellFormed` to support
recording a function parameter, allowing us to get the corresponding
HIR type if an error occurs. Function typechecking is modified to
pass this information during signature normalization and WF checking.
The resulting code is fairly verbose, due to the fact that we can
no longer normalize the entire signature with a single function call.
As part of the refactoring, we now perform HIR-based WF checking
for several other 'typed items' (statics, consts, and inherent impls).
As a result, WF and projection errors in a function signature now
have a precise span, which points directly at the responsible type.
If a function signature is constructed via a macro, this will allow
the error message to point at the code 'most responsible' for the error
(e.g. a user-supplied macro argument).
Better diagnostics with mismatched types due to implicit static lifetime
Fixes#78113
I think this is my first diagnostics PR...definitely happy to hear thoughts on the direction/implementation here.
I was originally just trying to solve the error above, where the lifetime on a GAT was causing a cryptic "mismatched types" error. But as I was writing this, I realized that this (unintentionally) also applied to a different case: `wf-in-foreign-fn-decls-issue-80468.rs`. I'm not sure if this diagnostic should get a new error code, or even reuse an existing one. And, there might be some ways to make this even more generalized. Also, the error is a bit more lengthy and verbose than probably needed. So thoughts there are welcome too.
This PR essentially ended up adding a new nice region error pass that triggers if a type doesn't match the self type of an impl which is selected because of a predicate because of an implicit static bound on that self type.
r? `@estebank`
Don't create references to uninitialized data in `List::from_arena`
Previously `result` and `arena_slice` were references pointing to uninitialized data, which is technically UB. They may have been fine because the pointed data is `Copy` and and they were only written to, but the semantics of this aren't clearly defined yet, and since we have a sound way to do the same thing I don't think we should keep the possibly-unsound way.
Remove nondeterminism in multiple-definitions test
Compare all fields in `DllImport` when sorting to avoid nondeterminism in the error for multiple inconsistent definitions of an extern function. Restore the multiple-definitions test.
Resolves#87084.
Make expansions stable for incr. comp.
This PR aims to make expansions stable for incr. comp. by using the same architecture as definitions:
- the interned identifier `ExpnId` contains a `CrateNum` and a crate-local id;
- bidirectional maps `ExpnHash <-> ExpnId` are setup;
- incr. comp. on-disk cache saves and reconstructs expansions using their `ExpnHash`.
I tried to use as many `LocalExpnId` as I could in the resolver code, but I may have missed a few opportunities.
All this will allow to use an `ExpnId` as a query key, and to force this query without recomputing caller queries. For instance, this will be used to implement #85999.
r? `@petrochenkov`
CTFE/Miri engine Pointer type overhaul
This fixes the long-standing problem that we are using `Scalar` as a type to represent pointers that might be integer values (since they point to a ZST). The main problem is that with int-to-ptr casts, there are multiple ways to represent the same pointer as a `Scalar` and it is unclear if "normalization" (i.e., the cast) already happened or not. This leads to ugly methods like `force_mplace_ptr` and `force_op_ptr`.
Another problem this solves is that in Miri, it would make a lot more sense to have the `Pointer::offset` field represent the full absolute address (instead of being relative to the `AllocId`). This means we can do ptr-to-int casts without access to any machine state, and it means that the overflow checks on pointer arithmetic are (finally!) accurate.
To solve this, the `Pointer` type is made entirely parametric over the provenance, so that we can use `Pointer<AllocId>` inside `Scalar` but use `Pointer<Option<AllocId>>` when accessing memory (where `None` represents the case that we could not figure out an `AllocId`; in that case the `offset` is an absolute address). Moreover, the `Provenance` trait determines if a pointer with a given provenance can be cast to an integer by simply dropping the provenance.
I hope this can be read commit-by-commit, but the first commit does the bulk of the work. It introduces some FIXMEs that are resolved later.
Fixes https://github.com/rust-lang/miri/issues/841
Miri PR: https://github.com/rust-lang/miri/pull/1851
r? `@oli-obk`
Update Rust Float-Parsing Algorithms to use the Eisel-Lemire algorithm.
# Summary
Rust, although it implements a correct float parser, has major performance issues in float parsing. Even for common floats, the performance can be 3-10x [slower](https://arxiv.org/pdf/2101.11408.pdf) than external libraries such as [lexical](https://github.com/Alexhuszagh/rust-lexical) and [fast-float-rust](https://github.com/aldanor/fast-float-rust).
Recently, major advances in float-parsing algorithms have been developed by Daniel Lemire, along with others, and implement a fast, performant, and correct float parser, with speeds up to 1200 MiB/s on Apple's M1 architecture for the [canada](0e2b5d163d/data/canada.txt) dataset, 10x faster than Rust's 130 MiB/s.
In addition, [edge-cases](https://github.com/rust-lang/rust/issues/85234) in Rust's [dec2flt](868c702d0c/library/core/src/num/dec2flt) algorithm can lead to over a 1600x slowdown relative to efficient algorithms. This is due to the use of Clinger's correct, but slow [AlgorithmM and Bellepheron](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.45.4152&rep=rep1&type=pdf), which have been improved by faster big-integer algorithms and the Eisel-Lemire algorithm, respectively.
Finally, this algorithm provides substantial improvements in the number of floats the Rust core library can parse. Denormal floats with a large number of digits cannot be parsed, due to use of the `Big32x40`, which simply does not have enough digits to round a float correctly. Using a custom decimal class, with much simpler logic, we can parse all valid decimal strings of any digit count.
```rust
// Issue in Rust's dec2fly.
"2.47032822920623272088284396434110686182e-324".parse::<f64>(); // Err(ParseFloatError { kind: Invalid })
```
# Solution
This pull request implements the Eisel-Lemire algorithm, modified from [fast-float-rust](https://github.com/aldanor/fast-float-rust) (which is licensed under Apache 2.0/MIT), along with numerous modifications to make it more amenable to inclusion in the Rust core library. The following describes both features in fast-float-rust and improvements in fast-float-rust for inclusion in core.
**Documentation**
Extensive documentation has been added to ensure the code base may be maintained by others, which explains the algorithms as well as various associated constants and routines. For example, two seemingly magical constants include documentation to describe how they were derived as follows:
```rust
// Round-to-even only happens for negative values of q
// when q ≥ −4 in the 64-bit case and when q ≥ −17 in
// the 32-bitcase.
//
// When q ≥ 0,we have that 5^q ≤ 2m+1. In the 64-bit case,we
// have 5^q ≤ 2m+1 ≤ 2^54 or q ≤ 23. In the 32-bit case,we have
// 5^q ≤ 2m+1 ≤ 2^25 or q ≤ 10.
//
// When q < 0, we have w ≥ (2m+1)×5^−q. We must have that w < 2^64
// so (2m+1)×5^−q < 2^64. We have that 2m+1 > 2^53 (64-bit case)
// or 2m+1 > 2^24 (32-bit case). Hence,we must have 2^53×5^−q < 2^64
// (64-bit) and 2^24×5^−q < 2^64 (32-bit). Hence we have 5^−q < 2^11
// or q ≥ −4 (64-bit case) and 5^−q < 2^40 or q ≥ −17 (32-bitcase).
//
// Thus we have that we only need to round ties to even when
// we have that q ∈ [−4,23](in the 64-bit case) or q∈[−17,10]
// (in the 32-bit case). In both cases,the power of five(5^|q|)
// fits in a 64-bit word.
const MIN_EXPONENT_ROUND_TO_EVEN: i32;
const MAX_EXPONENT_ROUND_TO_EVEN: i32;
```
This ensures maintainability of the code base.
**Improvements for Disguised Fast-Path Cases**
The fast path in float parsing algorithms attempts to use native, machine floats to represent both the significant digits and the exponent, which is only possible if both can be exactly represented without rounding. In practice, this means that the significant digits must be 53-bits or less and the then exponent must be in the range `[-22, 22]` (for an f64). This is similar to the existing dec2flt implementation.
However, disguised fast-path cases exist, where there are few significant digits and an exponent above the valid range, such as `1.23e25`. In this case, powers-of-10 may be shifted from the exponent to the significant digits, discussed at length in https://github.com/rust-lang/rust/issues/85198.
**Digit Parsing Improvements**
Typically, integers are parsed from string 1-at-a-time, requiring unnecessary multiplications which can slow down parsing. An approach to parse 8 digits at a time using only 3 multiplications is described in length [here](https://johnnylee-sde.github.io/Fast-numeric-string-to-int/). This leads to significant performance improvements, and is implemented for both big and little-endian systems.
**Unsafe Changes**
Relative to fast-float-rust, this library makes less use of unsafe functionality and clearly documents it. This includes the refactoring and documentation of numerous unsafe methods undesirably marked as safe. The original code would look something like this, which is deceptively marked as safe for unsafe functionality.
```rust
impl AsciiStr {
#[inline]
pub fn step_by(&mut self, n: usize) -> &mut Self {
unsafe { self.ptr = self.ptr.add(n) };
self
}
}
...
#[inline]
fn parse_scientific(s: &mut AsciiStr<'_>) -> i64 {
// the first character is 'e'/'E' and scientific mode is enabled
let start = *s;
s.step();
...
}
```
The new code clearly documents safety concerns, and does not mark unsafe functionality as safe, leading to better safety guarantees.
```rust
impl AsciiStr {
/// Advance the view by n, advancing it in-place to (n..).
pub unsafe fn step_by(&mut self, n: usize) -> &mut Self {
// SAFETY: same as step_by, safe as long n is less than the buffer length
self.ptr = unsafe { self.ptr.add(n) };
self
}
}
...
/// Parse the scientific notation component of a float.
fn parse_scientific(s: &mut AsciiStr<'_>) -> i64 {
let start = *s;
// SAFETY: the first character is 'e'/'E' and scientific mode is enabled
unsafe {
s.step();
}
...
}
```
This allows us to trivially demonstrate the new implementation of dec2flt is safe.
**Inline Annotations Have Been Removed**
In the previous implementation of dec2flt, inline annotations exist practically nowhere in the entire module. Therefore, these annotations have been removed, which mostly does not impact [performance](https://github.com/aldanor/fast-float-rust/issues/15#issuecomment-864485157).
**Fixed Correctness Tests**
Numerous compile errors in `src/etc/test-float-parse` were present, due to deprecation of `time.clock()`, as well as the crate dependencies with `rand`. The tests have therefore been reworked as a [crate](https://github.com/Alexhuszagh/rust/tree/master/src/etc/test-float-parse), and any errors in `runtests.py` have been patched.
**Undefined Behavior**
An implementation of `check_len` which relied on undefined behavior (in fast-float-rust) has been refactored, to ensure that the behavior is well-defined. The original code is as follows:
```rust
#[inline]
pub fn check_len(&self, n: usize) -> bool {
unsafe { self.ptr.add(n) <= self.end }
}
```
And the new implementation is as follows:
```rust
/// Check if the slice at least `n` length.
fn check_len(&self, n: usize) -> bool {
n <= self.as_ref().len()
}
```
Note that this has since been fixed in [fast-float-rust](https://github.com/aldanor/fast-float-rust/pull/29).
**Inferring Binary Exponents**
Rather than explicitly store binary exponents, this new implementation infers them from the decimal exponent, reducing the amount of static storage required. This removes the requirement to store [611 i16s](868c702d0c/library/core/src/num/dec2flt/table.rs (L8)).
# Code Size
The code size, for all optimizations, does not considerably change relative to before for stripped builds, however it is **significantly** smaller prior to stripping the resulting binaries. These binary sizes were calculated on x86_64-unknown-linux-gnu.
**new**
Using rustc version 1.55.0-dev.
opt-level|size|size(stripped)
|:-:|:-:|:-:|
0|400k|300K
1|396k|292K
2|392k|292K
3|392k|296K
s|396k|292K
z|396k|292K
**old**
Using rustc version 1.53.0-nightly.
opt-level|size|size(stripped)
|:-:|:-:|:-:|
0|3.2M|304K
1|3.2M|292K
2|3.1M|284K
3|3.1M|284K
s|3.1M|284K
z|3.1M|284K
# Correctness
The dec2flt implementation passes all of Rust's unittests and comprehensive float parsing tests, along with numerous other tests such as Nigel Toa's comprehensive float [tests](https://github.com/nigeltao/parse-number-fxx-test-data) and Hrvoje Abraham [strtod_tests](https://github.com/ahrvoje/numerics/blob/master/strtod/strtod_tests.toml). Therefore, it is unlikely that this algorithm will incorrectly round parsed floats.
# Issues Addressed
This will fix and close the following issues:
- resolves#85198
- resolves#85214
- resolves#85234
- fixes#31407
- fixes#31109
- fixes#53015
- resolves#68396
- closes https://github.com/aldanor/fast-float-rust/issues/15
Implementation is based off fast-float-rust, with a few notable changes.
- Some unsafe methods have been removed.
- Safe methods with inherently unsafe functionality have been removed.
- All unsafe functionality is documented and provably safe.
- Extensive documentation has been added for simpler maintenance.
- Inline annotations on internal routines has been removed.
- Fixed Python errors in src/etc/test-float-parse/runtests.py.
- Updated test-float-parse to be a library, to avoid missing rand dependency.
- Added regression tests for #31109 and #31407 in core tests.
- Added regression tests for #31109 and #31407 in ui tests.
- Use the existing slice primitive to simplify shared dec2flt methods
- Remove Miri ignores from dec2flt, due to faster parsing times.
- resolves#85198
- resolves#85214
- resolves#85234
- fixes#31407
- fixes#31109
- fixes#53015
- resolves#68396
- closes https://github.com/aldanor/fast-float-rust/issues/15
Add initial implementation of HIR-based WF checking for diagnostics
During well-formed checking, we walk through all types 'nested' in
generic arguments. For example, WF-checking `Option<MyStruct<u8>>`
will cause us to check `MyStruct<u8>` and `u8`. However, this is done
on a `rustc_middle::ty::Ty`, which has no span information. As a result,
any errors that occur will have a very general span (e.g. the
definintion of an associated item).
This becomes a problem when macros are involved. In general, an
associated type like `type MyType = Option<MyStruct<u8>>;` may
have completely different spans for each nested type in the HIR. Using
the span of the entire associated item might end up pointing to a macro
invocation, even though a user-provided span is available in one of the
nested types.
This PR adds a framework for HIR-based well formed checking. This check
is only run during error reporting, and is used to obtain a more precise
span for an existing error. This is accomplished by individually
checking each 'nested' type in the HIR for the type, allowing us to
find the most-specific type (and span) that produces a given error.
The majority of the changes are to the error-reporting code. However,
some of the general trait code is modified to pass through more
information.
Since this has no soundness implications, I've implemented a minimal
version to begin with, which can be extended over time. In particular,
this only works for HIR items with a corresponding `DefId` (e.g. it will
not work for WF-checking performed within function bodies).
During well-formed checking, we walk through all types 'nested' in
generic arguments. For example, WF-checking `Option<MyStruct<u8>>`
will cause us to check `MyStruct<u8>` and `u8`. However, this is done
on a `rustc_middle::ty::Ty`, which has no span information. As a result,
any errors that occur will have a very general span (e.g. the
definintion of an associated item).
This becomes a problem when macros are involved. In general, an
associated type like `type MyType = Option<MyStruct<u8>>;` may
have completely different spans for each nested type in the HIR. Using
the span of the entire associated item might end up pointing to a macro
invocation, even though a user-provided span is available in one of the
nested types.
This PR adds a framework for HIR-based well formed checking. This check
is only run during error reporting, and is used to obtain a more precise
span for an existing error. This is accomplished by individually
checking each 'nested' type in the HIR for the type, allowing us to
find the most-specific type (and span) that produces a given error.
The majority of the changes are to the error-reporting code. However,
some of the general trait code is modified to pass through more
information.
Since this has no soundness implications, I've implemented a minimal
version to begin with, which can be extended over time. In particular,
this only works for HIR items with a corresponding `DefId` (e.g. it will
not work for WF-checking performed within function bodies).
TAIT: Infer all inference variables in opaque type substitutions via InferCx
The previous algorithm was correct for the example given in its
documentation, but when the TAIT was declared as a free item
instead of an associated item, the generic parameters were the
wrong ones.
cc `@spastorino`
r? `@nikomatsakis`
The previous algorithm was correct for the example given in its
documentation, but when the TAIT was declared as a free item
instead of an associated item, the generic parameters were the
wrong ones.
Replace associated item bound vars with placeholders when projecting
Fixes#76407Fixes#76826
Similar, but more limited, to #85499. This allows us to handle things like `for<'a> <T as Trait>::Assoc<'a>` but not `for<'a> <T as Trait<'a>>::Assoc`, unblocking GATs.
r? `@nikomatsakis`
Add -Zfuture-incompat-test to assist with testing future-incompat reports.
This adds a `-Zfuture-incompat-test` cli flag to assist with testing future-incompatible reports. This flag causes all lints to be treated as a future-incompatible lint, and will emit a report for them. This is being added so that Cargo's testsuite can reliably test the reporting infrastructure. Right now, Cargo relies on using array_into_iter as a test subject. Since the breaking "future incompatible" lints are never intended to last forever, this means Cargo's testsuite would always need to keep changing to choose different lints (for example, #86330 proposed dropping that moniker for array_into_iter). With this flag, Cargo's tests can trigger any lint and check for the report.
This resolves all the problems we had around "normalizing" the representation of a Scalar in case it carries a Pointer value: we can just use Pointer if we want to have a value taht we are sure is already normalized.
CTFE engine: small cleanups
I noticed these while preparing a large PR, and figured I'd better send them ahead to not muddy the diff unnecessarily.
- remove remaining use of Pointer in Allocation API (I missed those in https://github.com/rust-lang/rust/pull/85472)
- remove unnecessary deallocate_local hack (this logic does not seem necessary any more)
r? `@oli-obk`
Simplify future incompatible reporting.
This simplifies the implementation of the future incompatible reporting system. Instead of having a separate field in the future_incompatible definition, this reuses the `FutureIncompatibilityReason` enum. It also drops the "date" field. Cargo does not use the date field, and there isn't much of a need for this to be structured, and I am skeptical that the date can be predicted reliably. The date or release version can be listed in the lint text if desired.
Revert the revert of renaming traits::VTable to ImplSource
As #72114 and #73055 were merged so closely together I think this
accidentally happened while rebasing
Support forwarding caller location through trait object method call
Since PR #69251, the `#[track_caller]` attribute has been supported on
traits. However, it only has an effect on direct (monomorphized) method
calls. Calling a `#[track_caller]` method on a trait object will *not*
propagate caller location information - instead, `Location::caller()` will
return the location of the method definition.
This PR forwards caller location information when `#[track_caller]` is
present on the method definition in the trait. This is possible because
`#[track_caller]` in this position is 'inherited' by any impls of that
trait, so all implementations will have the same ABI.
This PR does *not* change the behavior in the case where
`#[track_caller]` is present only on the impl of a trait.
While all implementations of the method might have an explicit
`#[track_caller]`, we cannot know this at codegen time, since other
crates may have impls of the trait. Therefore, we keep the current
behavior of not forwarding the caller location, ensuring that all
implementations of the trait will have the correct ABI.
See the modified test for examples of how this works
Add support for raw-dylib with stdcall, fastcall functions
Next stage of work for #58713: allow `extern "stdcall"` and `extern "fastcall"` with `#[link(kind = "raw-dylib")]`.
I've deliberately omitted support for vectorcall, as that doesn't currently work, and I wanted to get this out for review. (I haven't really investigated the vectorcall failure much yet, but at first (very cursory) glance it appears that the problem is elsewhere.)
- 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.
Previously, debuggers print closures as something like
```
y::main::closure-0 (0x7fffffffdd34)
```
The pointer actually references to an upvar. It is not
very obvious, especially for beginners.
It's because upvars don't have names before, as they
are packed into a tuple. This commit names the upvars,
so we can expect to see something like
```
y::main::closure-0 {_captured_ref__b: 0x[...]}
```
The `large_assignments` lints detects moves over specified limit. The
limit is configured through `move_size_limit = "N"` attribute placed at
the root of a crate. When attribute is absent, the lint is disabled.
Make it possible to enable the lint without making any changes to the
source code, through a new flag `-Zmove-size-limit=N`. For example, to
detect moves exceeding 1023 bytes in a cargo crate, including all
dependencies one could use:
```
$ env RUSTFLAGS=-Zmove-size-limit=1024 cargo build -vv
```
Query-ify global limit attribute handling
Currently, we read various 'global limits' from inner attributes the crate root (`recursion_limit`, `move_size_limit`, `type_length_limit`, `const_eval_limit`). These limits are then stored in `Sessions`, allowing them to be access from a `TyCtxt` without registering a dependency on the crate root attributes.
This PR moves the calculation of these global limits behind queries, so that we properly track dependencies on crate root attributes. During the setup of macro expansion (before we've created a `TyCtxt`), we need to access the recursion limit, which is now done by directly calling into the code shared by the normal query implementations.
Hack: Ignore inference variables in certain queries
Fixes#84841Fixes#86753
Some queries are not built to accept types with inference variables, which can lead to ICEs. These queries probably ought to be converted to canonical form, but as a quick workaround, we can return conservative results in the case that inference variables are found.
We should file a follow-up issue (and update the FIXMEs...) to do the proper refactoring.
cc `@arora-aman`
r? `@oli-obk`
Support allocation failures when interpreting MIR
This closes#79601 by handling the case where memory allocation fails during MIR interpretation, and translates that failure into an `InterpError`. The error message is "tried to allocate more memory than available to compiler" to make it clear that the memory shortage is happening at compile-time by the compiler itself, and that it is not a runtime issue.
Now that memory allocation can fail, it would be neat if Miri could simulate low-memory devices to make it easy to see how much memory a Rust program needs.
Note that this breaks Miri because it assumes that allocation can never fail.
Fix ICE when `main` is declared in an `extern` block
Changes in #84401 to implement `imported_main` changed how the crate entry point is found, and a declared `main` in an `extern` block was detected erroneously. This was causing the ICE described in #86110.
This PR adds a check for this case and emits an error instead. Previously a `main` declaration in an `extern` block was not detected as an entry point at all, so emitting an error shouldn't break anything that worked previously. In 1.52.1 stable this is demonstrated, with a `` `main` function not found`` error.
Fixes#86110
Remove unused dependencies from compiler crates
Various compiler crates have dependencies that they don't appear to use. I used some scripting to detect such dependencies, filtered them based on some manual review, and removed those that do indeed appear to be entirely unused.
Introduce -Zprofile-closures to evaluate the impact of 2229
This creates a CSV with name "closure_profile_XXXXX.csv", where the
variable part is the process id of the compiler.
To profile a cargo project you can run one of the following depending on
if you're compiling a library or a binary:
```
cargo +nightly rustc --lib -- -Zprofile-closures
cargo +nightly rustc --bin {binary_name} -- -Zprofile-closures
```
r? `@nikomatsakis`
Change vtable memory representation to use tcx allocated allocations.
This fixes https://github.com/rust-lang/rust/issues/86324. However i suspect there's more to change before it can land.
r? `@bjorn3`
cc `@rust-lang/miri`
Turn non_fmt_panic into a future_incompatible edition lint.
This turns the `non_fmt_panic` lint into a future_incompatible edition lint, so it becomes part of the `rust_2021_compatibility` group. See https://github.com/rust-lang/rust/issues/85894.
This lint produces both warnings about semantical changes (e.g. `panic!("{{")`) and things that will become hard errors (e.g. `panic!("{")`). So I added a `explain_reason: false` that supresses the default "this will become a hard error" or "the semantics will change" message, and instead added a note depending on the situation. (cc `@rylev)`
r? `@nikomatsakis`
This creates a CSV with name "closure_profile_XXXXX.csv", where the
variable part is the process id of the compiler.
To profile a cargo project you can run one of the following depending on
if you're compiling a library or a binary:
```
cargo +stage1 rustc --lib -- -Zprofile-closures
cargo +stage1 rustc --bin -- -Zprofile-closures
```
Use HTTPS links where possible
While looking at #86583, I wondered how many other (insecure) HTTP links were in `rustc`. This changes most other `http` links to `https`. While most of the links are in comments or documentation, there are a few other HTTP links that are used by CI that are changed to HTTPS.
Notes:
- I didn't change any to or in licences
- Some links don't support HTTPS :(
- Some `http` links were dead, in those cases I upgraded them to their new places (all of which used HTTPS)
