Give `global_asm` a fake body to store typeck results, represent `sym fn` as a hir expr to fix `sym fn` operands with lifetimes
There are a few intertwined problems with `sym fn` operands in both inline and global asm macros.
Specifically, unlike other anon consts, they may evaluate to a type with free regions in them without actually having an item-level type annotation to give them a "proper" type. This is in contrast to named constants, which always have an item-level type annotation, or unnamed constants which are constrained by their position (e.g. a const arg in a turbofish, or a const array length).
Today, we infer the type of the operand by looking at the HIR typeck results; however, those results are region-erased, so during borrowck we ICE since we don't expect to encounter erased regions. We can't just fill this type with something like `'static`, since we may want to use real (free) regions:
```rust
fn foo<'a>() {
asm!("/* ... */", sym bar::<&'a ()>);
}
```
The first idea may be to represent `sym fn` operands using *inline* consts instead of anon consts. This makes sense, since inline consts can reference regions from the parent body (like the `'a` in the example above). However, this introduces a problem with `global_asm!`, which doesn't *have* a parent body; inline consts *must* be associated with a parent body since they are not a body owner of their own. In #116087, I attempted to fix this by using two separate `sym` operands for global and inline asm. However, this led to a lot of confusion and also some unattractive code duplication.
In this PR, I adjust the lowering of `global_asm!` so that it's lowered in a "fake" HIR body. This body contains a single expression which is `ExprKind::InlineAsm`; we don't *use* this HIR body, but it's used in typeck and borrowck so that we can properly infer and validate the the lifetimes of `sym fn` operands.
I then adjust the lowering of `sym fn` to instead be represented with a HIR expression. This is both because it's no longer necessary to represent this operand as an anon const, since it's *just* a path expression, and also more importantly to sidestep yet another ICE (https://github.com/rust-lang/rust/issues/137179), which has to do with the existing code breaking an invariant of def-id creation and anon consts. Specifically, we are not allowed to synthesize a def-id for an anon const when that anon const contains expressions with def-ids whose parent is *not* that anon const. This is somewhat related to https://github.com/rust-lang/rust/pull/130443#issuecomment-2445678945, which is also a place in the compiler where synthesizing anon consts leads to def-id parenting issue.
As a side-effect, this consolidates the type checking for inline and global asm, so it allows us to simplify `InlineAsmCtxt` a bit. It also allows us to delete a bit of hacky code from anon const `type_of` which was there to detect `sym fn` operands specifically. This also could be generalized to support `const` asm operands with types with lifetimes in them. Since we specifically reject these consts today, I'm not going to change the representation of those consts (but they'd just be turned into inline consts).
r? oli-obk -- mostly b/c you're patient and also understand the breadth of the code that this touches, please reassign if you don't want to review this.
Fixes#111709Fixes#96304Fixes#137179
```rust
let mut tmp = vec![1, 2, 3];
for b in &mut tmp {
*b = !*b;
}
```
must not suggest the invalid `tmp.fill(!*b)`.
In addition, there is another commit which cleans up two function calls
with no effect.
Fix#14189
changelog: [`manual_slice_fill`]: ensure that the initialization
expression doesn't reference the iterator
More sophisticated span trimming for suggestions
Previously #136958 only cared about prefixes or suffixes. Now it detects more cases where a suggestion is "sandwiched" by unchanged code on the left or the right. Would be cool if we could detect several insertions, like `ACE` going to `ABCDE`, extracting `B` and `D`, but that seems unwieldy.
r? `@estebank`
- The name of an MSRV alias should describe its functionality, and it is
not appropriate for it to be the same as the name of the lint that uses
it.
- Additionally, while `manual_div_ceil` allows setting MSRV, this is not
correctly reflected in the configuration information.
changelog: none
Simplify `Postorder` customization.
`Postorder` has a `C: Customization<'tcx>` parameter, that gives it flexibility about how it computes successors. But in practice, there are only two `impls` of `Customization`, and one is for the unit type.
This commit simplifies things by removing the generic parameter and replacing it with an `Option`.
r? ````@saethlin````
For some reason, the `todo!` and `unimplemented!` macros were not included in the list of format-supporting macros list. Since they seem to behave exactly the same as all others like `write!` and `assert!`, adding them now.
Roses are red,
Biolets are blue,
A typo happened,
too late now
You might be asking,
what are Biolets now?
And to be honest,
I have no clue
---
The cat of this release is `Vera` nominated by @and-reas-se
<img height=500
src="https://github.com/user-attachments/assets/82e6fccc-1f6d-4d29-b6bb-0bd4f3584593"
alt="The cats of this Clippy release" />
Cats for the next release can be nominated in the comments :D
---
changelog: none
`Postorder` has a `C: Customization<'tcx>` parameter, that gives it
flexibility about how it computes successors. But in practice, there are
only two `impls` of `Customization`, and one is for the unit type.
This commit simplifies things by removing the generic parameter and
replacing it with an `Option`.
Lint `#[must_use]` attributes applied to methods in trait impls
The `#[must_use]` attribute has no effect when applied to methods in trait implementations. This PR adds it to the unused `#[must_use]` lint, and cleans the extra attributes in portable-simd and Clippy.
fixes#13934
I modified the part for checking if the map is used so that it can check
field and index exprs.
changelog: [`map_entry`]: fix FP on struct member
In the case where `iter` is a `DoubleEndedIterator`, replacing a call to
`iter.last()` (which consumes `iter`) by `iter.next_back()` (which
requires a mutable reference to `iter`) cannot be done when `iter` is a
non-mutable binding which is not a mutable reference. When possible, a
local immutable binding is made into a mutable one.
Also, the applicability is switched to `MaybeIncorrect` and a note is
added to the output when the element types have a significant drop,
because the drop order will potentially be modified because
`.next_back()` does not consume the iterator nor the elements before the
last one.
Fix#14139
changelog: [`double_ended_iterator_last`]: do not trigger on
non-reference immutable receiver, and warn about possible drop order
change
`iter.last()` will drop all elements of `iter` in order, while
`iter.next_back()` will drop the non-last elements of `iter` when
`iter` goes out of scope since `.next_back()` does not consume its
argument.
When the transformation proposed by `double_ended_iterator_last` would
concern an iterator whose element type has a significant drop, a note is
added to warn about the possible drop order change, and the suggestion
is switched from `MachineApplicable` to `MaybeIncorrect`.
In the case where `iter` is a `DoubleEndedIterator`, replacing a call to
`iter.last()` (which consumes `iter`) by `iter.next_back()` (which
requires a mutable reference to `iter`) cannot be done when `iter`
Is not a mutable binding or a mutable reference.
When `iter` is a local binding, it can be made mutable by fixing its
definition site.
