Elaborate trait assumption in `receiver_is_dispatchable`
Fixes#138172. See comment on the linked test.
Probably not a fix for the general problem, bc I think this may still be incomplete for other weird `where` clauses on the receiver. But 🤷, supertraits seems like an obvious one to fix.
Consolidate and improve error messaging for `CoerceUnsized` and `DispatchFromDyn`
Firstly, this PR consolidates and reworks the error diagnostics for `CoercePointee` and `DispatchFromDyn`. There was a ton of duplication for no reason -- this reworks both the errors and also the error codes, since they can be shared between both traits since they report the same thing.
Secondly, when encountering a struct with multiple fields that must be coerced, point out the field spans, rather than mentioning the fields by name. This makes the error message clearer, but also means that we don't mention the `__S` dummy parameter for `derive(CoercePointee)`.
Thirdly, emit a custom error message when we encounter a trait error that comes from the recursive field `CoerceUnsized`/`DispatchFromDyn` trait check. **Note:** This is the only one I'm not too satisfied with -- I think it could use some more refinement, but ideally it explains that the field must be an unsize-able pointer... Feedback welcome.
Finally, don't emit `DispatchFromDyn` validity errors if we detect `CoerceUnsized` validity errors from an impl of the same ADT.
This is best reviewed per commit.
r? `@oli-obk` perhaps?
cc `@dingxiangfei2009` -- sorry for making my own attempt at this PR, but I wanted to see if I could implement a fix for #136796 in a less complicated way, since communicating over github review comments can be a bit slow. I'll leave comments inline to explain my thinking about the diagnostics changes.
Delay bug when method confirmation cannot upcast object pick of self
Justification is on the test comment. Simply delays a bug that we were previously ICEing on.
cc ``@adetaylor`` since this is a `arbitrary_self_types` ICE.
```
error[E0610]: `{integer}` is a primitive type and therefore doesn't have fields
--> $DIR/attempted-access-non-fatal.rs:7:15
|
LL | let _ = 2.l;
| ^
|
help: if intended to be a floating point literal, consider adding a `0` after the period and a `f64` suffix
|
LL - let _ = 2.l;
LL + let _ = 2.0f64;
|
```
Make sure to use `Receiver` trait when extracting object method candidate
In method confirmation, the `extract_existential_trait_ref` function re-extracts the object type by derefing until it reaches an object. If we're assembling methods via the `Receiver` trait, make sure we re-do our work also using the receiver trait.
Fixes#135155
cc ``@adetaylor``
Arbitrary self types v2: recursion test
Add a test for infinite recursion of an arbitrary self type.
These diagnostics aren't perfect (especially the repetition of the statement that there's too much recursion) but for now at least let's add a test to confirm that such diagnostics are emitted.
As suggested by ```@oli-obk```
Relates to #44874
r? ```@wesleywiser```
Add a test for infinite recursion of an arbitrary self type.
These diagnostics aren't perfect (especially the repetition of the
statement that there's too much recursion) but for now at least
let's add a test to confirm that such diagnostics are emitted.
Compiler: Finalize dyn compatibility renaming
Update the Reference link to use the new URL fragment from https://github.com/rust-lang/reference/pull/1666 (this change has finally hit stable). Fixes a FIXME.
Follow-up to #130826.
Part of #130852.
~~Blocking it on #133372.~~ (merged)
r? ghost
This CL makes a number of small changes to dyn compatibility errors:
- "object safety" has been renamed to "dyn-compatibility" throughout
- "Convert to enum" suggestions are no longer generated when there
exists a type-generic impl of the trait or an impl for `dyn OtherTrait`
- Several error messages are reorganized for user readability
Additionally, the dyn compatibility error creation code has been
split out into functions.
cc #132713
cc #133267
Do not consider traits that have unsatisfied const conditions to be conditionally const
This will improve error messages as we continue to constify traits, since we don't want to start calling things "conditionally const" if they aren't implemented with a const impl anyways.
The only case that this affects today is `Deref` since that's one of the only constified traits in the standard library :)
r? RalfJung
Improve `DispatchFromDyn` and `CoerceUnsized` impl validation
* Disallow arbitrary 1-ZST fields in `DispatchFromDyn` -- only `PhantomData`, and 1-ZSTs that mention no params (which is needed to support, e.g., the `Global` alloctor in `Box<T, U = Global>`).
* Don't allow coercing between non-ZSTs to ZSTs (since the previous check wasn't actually checking the field tys were the same before checking the layout...)
* Normalize the field before checking it's `PhantomData`.
Fixes#135215Fixes#135214Fixes#135220
r? ```@BoxyUwU``` or reassign
Arbitrary self types v2: no deshadow pre feature.
The arbitrary self types v2 work introduces a check for shadowed methods, whereby a method in some "outer" smart pointer type may called in preference to a method in the inner referent. This is bad if the outer pointer adds a method later, as it may change behavior, so we ensure we error in this circumstance.
It was intended that this new shadowing detection system only comes into play for users who enable the `arbitrary_self_types` feature (or of course everyone later if it's stabilized). It was believed that the new deshadowing code couldn't be reached without building the custom smart pointers that `arbitrary_self_types` enables, and therefore there was no risk of this code impacting existing users.
However, it turns out that cunning use of `Pin::get_ref` can cause this type of shadowing error to be emitted now. This commit adds a test for this case.
As we want this test to pass without arbitrary_self_types, but fail with it, I've split it into two files (one with run-pass and one without). If there's a better way I can amend it.
Part of #44874
r? ```@wesleywiser```
The arbitrary self types v2 work introduces a check for shadowed
methods, whereby a method in some "outer" smart pointer type may called
in preference to a method in the inner referent. This is bad if the
outer pointer adds a method later, as it may change behavior, so we
ensure we error in this circumstance.
It was intended that this new shadowing detection system only comes into
play for users who enable the `arbitrary_self_types` feature (or of
course everyone later if it's stabilized). It was believed that the
new deshadowing code couldn't be reached without building the custom
smart pointers that `arbitrary_self_types` enables, and therefore there
was no risk of this code impacting existing users.
However, it turns out that cunning use of `Pin::get_ref` can cause
this type of shadowing error to be emitted now. This commit adds a test
for this case.
Arbitrary self types v2 attempts to detect cases where methods in an
"outer" type (e.g. a smart pointer) might "shadow" methods in the
referent.
There are a couple of cases where the current code makes no attempt to
detect such shadowing. Both of these cases only apply if other unstable
features are enabled.
Add a test, mostly for illustrative purposes, so we can see the
shadowing cases that can occur.
Various types can be used as method receivers, such as Rc<>, Box<> and
Arc<>. The arbitrary self types v2 work allows further types to be made
method receivers by implementing the Receiver trait.
With that in mind, it may come as a surprise to people when certain
common types do not implement Receiver and thus cannot be used as a
method receiver.
The RFC for arbitrary self types v2 therefore proposes emitting specific
lint hints for these cases:
* NonNull
* Weak
* Raw pointers
The code already emits a hint for this third case, in that it advises
folks that the `arbitrary_self_types_pointers` feature may meet their
need. This PR adds diagnostic hints for the Weak and NonNull cases.
The recently landed PR to adjust arbitrary self types was a bit
overenthusiastic, advising folks to use the new Receiver trait even
before it's been stabilized. Revert to the older wording of the lint in
such cases.
There's some discussion on the RFC about whether generic receivers should be
allowed, but in the end the conclusion was that they should be blocked
(at least for some definition of 'generic'). This blocking landed in
an earlier PR; this commit adds additional tests to ensure the
interaction with the rest of the Arbitrary Self Types v2 feature is as
expected. This test may be a little duplicative but it seems better
to land it than not.
In this new version of Arbitrary Self Types, we no longer use the Deref trait
exclusively when working out which self types are valid. Instead, we follow a
chain of Receiver traits. This enables methods to be called on smart pointer
types which fundamentally cannot support Deref (for instance because they are
wrappers for pointers that don't follow Rust's aliasing rules).
This includes:
* Changes to tests appropriately
* New tests for:
* The basics of the feature
* Ensuring lifetime elision works properly
* Generic Receivers
* A copy of the method subst test enhanced with Receiver
This is really the heart of the 'arbitrary self types v2' feature, and
is the most critical commit in the current PR.
Subsequent commits are focused on:
* Detecting "shadowing" problems, where a smart pointer type can hide
methods in the pointee.
* Diagnostics and cleanup.
Naming: in this commit, the "Autoderef" type is modified so that it no
longer solely focuses on the "Deref" trait, but can now consider the
"Receiver" trait instead. Should it be renamed, to something like
"TraitFollower"? This was considered, but rejected, because
* even in the Receiver case, it still considers built-in derefs
* the name Autoderef is short and snappy.
The RFC for arbitrary self types v2 declares that we should reject
"generic" self types. This commit does so.
The definition of "generic" was unclear in the RFC, but has been
explored in
https://github.com/rust-lang/rust/issues/129147
and the conclusion is that "generic" means any `self` type which
is a type parameter defined on the method itself, or references
to such a type.
This approach was chosen because other definitions of "generic"
don't work. Specifically,
* we can't filter out generic type _arguments_, because that would
filter out Rc<Self> and all the other types of smart pointer
we want to support;
* we can't filter out all type params, because Self itself is a
type param, and because existing Rust code depends on other
type params declared on the type (as opposed to the method).
This PR decides to make a new error code for this case, instead of
reusing the existing E0307 error. This makes the code a
bit more complex, but it seems we have an opportunity to provide
specific diagnostics for this case so we should do so.
This PR filters out generic self types whether or not the
'arbitrary self types' feature is enabled. However, it's believed
that it can't have any effect on code which uses stable Rust, since
there are no stable traits which can be used to indicate a valid
generic receiver type, and thus it would have been impossible to
write code which could trigger this new error case.
It is however possible that this could break existing code which
uses either of the unstable `arbitrary_self_types` or
`receiver_trait` features. This breakage is intentional; as
we move arbitrary self types towards stabilization we don't want
to continue to support generic such types.
This PR adds lots of extra tests to arbitrary-self-from-method-substs.
Most of these are ways to trigger a "type mismatch" error which
9b82580c73/compiler/rustc_hir_typeck/src/method/confirm.rs (L519)
hopes can be minimized by filtering out generics in this way.
We remove a FIXME from confirm.rs suggesting that we make this change.
It's still possible to cause type mismatch errors, and a subsequent
PR may be able to improve diagnostics in this area, but it's harder
to cause these errors without contrived uses of the turbofish.
This is a part of the arbitrary self types v2 project,
https://github.com/rust-lang/rfcs/pull/3519https://github.com/rust-lang/rust/issues/44874
r? @wesleywiser
Compiler & its UI tests: Rename remaining occurrences of "object safe" to "dyn compatible"
Follow-up to #130826.
Part of #130852.
1. 1st commit: Fix stupid oversights. Should've been part of #130826.
2. 2nd commit: Rename the unstable feature `object_safe_for_dispatch` to `dyn_compatible_for_dispatch`. Might not be worth the churn, you decide.
3. 3rd commit: Apply the renaming to all UI tests (contents and paths).
