Disallow function pointers to #[rustc_args_required_const]
This commit disallows acquiring a function pointer to functions tagged as
`#[rustc_args_required_const]`. This is intended to be used as future-proofing
for the stdsimd crate to avoid taking a function pointer to any intrinsic which
has a hard requirement that one of the arguments is a constant value.
Note that the first commit here isn't related specifically to this feature, but was necessary to get this working in stdsimd!
NLL: Limit two-phase borrows to autoref-introduced borrows
This imposes a restriction on two-phase borrows so that it only applies to autoref-introduced borrows.
The goal is to ensure that our initial deployment of two-phase borrows is very conservative. We want it to still cover the `v.push(v.len());` example, but we do not want it to cover cases like `let imm = &v; let mu = &mut v; mu.push(imm.len());`
(Why do we want it to be conservative? Because when you are not conservative, then the results you get, at least with the current analysis, are tightly coupled to details of the MIR construction that we would rather remain invisible to the end user.)
Fix#46747
I decided, for this PR, to add a debug-flag `-Z two-phase-beyond-autoref`, to re-enable the more general approach. But my intention here is *not* that we would eventually turn on that debugflag by default; the main reason I added it was that I thought it was useful for writing tests to be able to write source that looks like desugared MIR.
This commit disallows acquiring a function pointer to functions tagged as
`#[rustc_args_required_const]`. This is intended to be used as future-proofing
for the stdsimd crate to avoid taking a function pointer to any intrinsic which
has a hard requirement that one of the arguments is a constant value.
Namely, the mutable borrows also carries a flag indicating whether
they should support two-phase borrows.
This allows us to thread down, from the point of the borrow's
introduction, whether the particular adjustment that created it is one
that yields two-phase mutable borrows.
Warn about more ignored bounds in type aliases
It seems that all bounds in type aliases are entirely ignored, not just type bounds. This extends the warning appropriately.
I assume this should be made a hard error with the next epoch? I can't see any reason to accept these programs. (And suddenly enforcing these type bounds would be a breaking change.)
Previously, when the type of a method receiver could not be determined,
the error message would, potentially confusingly, highlight the span of
the entire method call.
Resolves#36598, resolves#42234.
rustc: prefer ParamEnvAnd and LayoutCx over tuples for LayoutOf.
This PR provides `tcx.layout_of(param_env.and(ty))` as the idiomatic replacement for the existing `(tcx, param_env).layout_of(ty)` and removes fragile (coherence-wise) layout-related tuple impls.
r? @nikomatsakis
Tweak presentation on lifetime trait mismatch
- On trait/impl method discrepancy, add label pointing at trait signature.
- Point only at method definition when referring to named lifetimes on lifetime mismatch.
- When the sub and sup expectations are the same, tweak the output to avoid repeated spans.
Fix#30790, CC #18759.
remove intercrate ambiguity hints
The scheme was causing overflows during coherence checking (e.g. #47139). This is sort of a temporary fix; the proper fix I think involves reworking trait selection in deeper ways.
cc @sgrif -- this *should* fix diesel
cc @qnighy -- I'd like to discuss you with alternative techniques for achieving the same end. =) Actually, it might be good to put some energy into refactoring traits first.
r? @eddyb
- On mismatch between impl and trait method, point at the trait
signature.
- Point only at the method signature instead of the whole body on
trait/impl mismatch errors.
do not ICE when return type includes unconstrained anon region
It turns out that this *can* happen after all, if the region is only
used in projections from the input types.
Fixes https://github.com/rust-lang/rust/issues/47511
r? @eddyb
Fix into() cast paren check precedence
As discussed in #47699 the logic for determining if an expression needs parenthesis when suggesting an `.into()` cast is incorrect. Two broken examples from nightly are:
```
error[E0308]: mismatched types
--> main.rs:4:10
|
4 | test(foo as i8);
| ^^^^^^^^^ expected i32, found i8
help: you can cast an `i8` to `i32`, which will sign-extend the source value
|
4 | test(foo as i8.into());
|
```
```
error[E0308]: mismatched types
--> main.rs:4:10
|
4 | test(*foo);
| ^^^^ expected i32, found i8
help: you can cast an `i8` to `i32`, which will sign-extend the source value
|
4 | test(*foo.into());
|
```
As suggested by @petrochenkov switch the precedence check to `PREC_POSTFIX`. This catches both `as` and unary operators. Fixes#47699.
r? @petrochenkov
On missing method do not suggest private traits
When encountering a method call for an ADT that doesn't have any
implementation of it, we search for traits that could be implemented
that do have that method. Filter out private non-local traits that would
not be able to be implemented.
This doesn't account for public traits that are in a private scope, but
works as a first approximation and is a more correct behavior than the
current one.
Fix#45781.
As discussed in #47699 the logic for determining if an expression needs
parenthesis when suggesting an `.into()` cast is incorrect. Two broken
examples from nightly are:
```
error[E0308]: mismatched types
--> main.rs:4:10
|
4 | test(foo as i8);
| ^^^^^^^^^ expected i32, found i8
help: you can cast an `i8` to `i32`, which will sign-extend the source value
|
4 | test(foo as i8.into());
|
```
```
error[E0308]: mismatched types
--> main.rs:4:10
|
4 | test(*foo);
| ^^^^ expected i32, found i8
help: you can cast an `i8` to `i32`, which will sign-extend the source value
|
4 | test(*foo.into());
|
```
As suggested by @petrochenkov switch the precedence check to
PREC_POSTFIX. This catches both `as` and unary operators. Fixes#47699.
Create the concept of an `StructuredDiagnostic` that is self-contained
with enough knowledge of all variables to create a `DiagnosticBuilder`,
including different possible versions (one line output and expanded
explanations).
When encountering a method call for an ADT that doesn't have any
implementation of it, we search for traits that could be implemented
that do have that method. Filter out private non-local traits that would
not be able to be implemented.
This doesn't account for public traits that are in a private scope, but
works as a first approximation and is a more correct behavior than the
current one.
Implement repr(transparent)
r? @eddyb for the functional changes. The bulk of the PR is error messages and docs, might be good to have a doc person look over those.
cc #43036
cc @nox
