`E0229`: Suggest Moving Type Constraints to Type Parameter Declaration
Fixes#113073
This PR suggests `impl<T: Bound> Trait<T> for Foo` when finding `impl Trait<T: Bound> for Foo`. Tangentially, it also improves a handful of other error messages.
It accomplishes this in two steps:
1. Check if constrained arguments and parameter names appear in the same order and delay emitting "incorrect number of generic arguments" error because it can be confusing for the programmer to see `0 generic arguments provided` when there are `n` constrained generic arguments.
2. Inside `E0229`, suggest declaring the type parameter right after the `impl` keyword by finding the relevant impl block's span for type parameter declaration. This also handles lifetime declarations correctly.
Also, the multi part suggestion doesn't use the fluent error mechanism because translating all the errors to fluent style feels outside the scope of this PR. I will handle it in a separate PR if this gets approved.
change method resolution to constrain hidden types instead of rejecting method candidates
Some of these are in probes and may affect inference. This is therefore a breaking change.
This allows new code to compile on stable:
```rust
trait Trait {}
impl Trait for u32 {}
struct Bar<T>(T);
impl Bar<u32> {
fn foo(self) {}
}
fn foo(x: bool) -> Bar<impl Sized> {
if x {
let x = foo(false);
x.foo();
//^ this used to not find the `foo` method, because while we did equate `x`'s type with possible candidates, we didn't allow opaque type inference while doing so
}
todo!()
}
```
r? ```````@compiler-errors```````
fixes #121404
cc https://github.com/rust-lang/rust/issues/116652
const-eval: make lint scope computation consistent
The first commit is some renaming for consistency, but otherwise unrelated. It just didn't feel worth a separate PR, but I can split this up if you prefer.
r? ``@oli-obk``
Tweak output of import suggestions
When both `std::` and `core::` items are available, only suggest the `std::` ones. We ensure that in `no_std` crates we suggest `core::` items.
Ensure that the list of items suggested to be imported are always in the order of local crate items, `std`/`core` items and finally foreign crate items.
Tweak wording of import suggestion: if there are multiple items but they are all of the same kind, we use the kind name and not the generic "items".
Fix#83564.
Add pub struct with allow(dead_code) into worklist
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Fixes#126289
When both `std::` and `core::` items are available, only suggest the
`std::` ones. We ensure that in `no_std` crates we suggest `core::`
items.
Ensure that the list of items suggested to be imported are always in the
order of local crate items, `std`/`core` items and finally foreign crate
items.
Tweak wording of import suggestion: if there are multiple items but they
are all of the same kind, we use the kind name and not the generic "items".
Fix#83564.
Implement lint for obligations broken by never type fallback change
This is the second (and probably last major?) lint required for the never type fallback change.
The idea is to check if the code errors with `fallback = ()` and if it errors with `fallback = !` and if it went from "ok" to "error", lint.
I'm not happy with the diagnostic, ideally we'd highlight what bound is the problem. But I'm really unsure how to do that (cc `@jackh726,` iirc you had some ideas?)
r? `@compiler-errors`
Thanks `@BoxyUwU` with helping with trait solver stuff when I was implementing the initial version of this lint.
Tracking:
- https://github.com/rust-lang/rust/issues/123748
Add a new trait to retrieve StableMir definition Ty
We implement the trait only for definitions that should have a type. It's possible that I missed a few definitions, but we can add them later if needed.
Fixes https://github.com/rust-lang/project-stable-mir/issues/80
Make `try_from_target_usize` method public
There is now no way to create a TyConst from an integer, so I propose making this method public unless there was a reason for keeping it otherwise.
safe transmute: support `Single` enums
Previously, the implementation of `Tree::from_enum` incorrectly treated enums with `Variants::Single` and `Variants::Multiple` identically. This is incorrect for `Variants::Single` enums, which delegate their layout to that of a variant with a particular index (or no variant at all if the enum is empty).
This flaw manifested first as an ICE. `Tree::from_enum` attempted to compute the tag of variants other than the one at `Variants::Single`'s `index`, and fell afoul of a sanity-checking assertion in `compiler/rustc_const_eval/src/interpret/discriminant.rs`. This assertion is non-load-bearing, and can be removed; the routine its in is well-behaved even without it.
With the assertion removed, the proximate issue becomes apparent: calling `Tree::from_variant` on a variant that does not exist is ill-defined. A sanity check the given variant has `FieldShapes::Arbitrary` fails, and the analysis is (correctly) aborted with `Err::NotYetSupported`.
This commit corrects this chain of failures by ensuring that `Tree::from_variant` is not called on variants that are, as far as layout is concerned, nonexistent. Specifically, the implementation of `Tree::from_enum` is now partitioned into three cases:
1. enums that are uninhabited
2. enums for which all but one variant is uninhabited
3. enums with multiple inhabited variants
`Tree::from_variant` is now only invoked in the third case. In the first case, `Tree::uninhabited()` is produced. In the second case, the layout is delegated to `Variants::Single`'s index.
Fixes#125811
docs(rustc): Improve discoverable of Cargo docs
In preparing Cargo's blog post for 1.80, I tried to find the documentation for the lint configuration and I couldn't. The link is only visible from the lint itself, which isn't where I started, and the side bar, which was collapsed for me.
The first place I went was the docs for `unexpected_cfgs` because this is configuration for that lint. If using lint configuration were a one off, I could see skipping it here. However, when we discussed this with at least one T-compiler member, there was interest in using this for other lints in the future. To that end, it seems like we should be exposing this with the lint itself.
The second place I checked was the `check-cfg` documentation. This now has a call out for the sub-page.
Urls to docs in rust_hir
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Harmonize using root or leaf obligation in trait error reporting
When #121826 changed the error reporting to use root obligation and not the leafmost obligation, it didn't actually make sure that all the other diagnostics helper functions used the right obligation.
Specifically, when reporting similar impl candidates we are looking for impls of the root obligation, but trying to match them against the trait ref of the leaf obligation.
This does a few other miscellaneous changes. There's a lot more clean-up that could be done here, but working with this code is really grief-inducing due to how messy it has become over the years. Someone really needs to show it love. 😓
r? ``@estebank``
Fixes#126129
Walk into alias-eq nested goals even if normalization fails
Somewhat broken due to the fact that we don't handle aliases well, nor do we handle ambiguities well. Still want to put up this incremental piece, since it improves type errors for projections whose trait refs are not satisfied.
r? lcnr
Previously, the implementation of `Tree::from_enum` incorrectly
treated enums with `Variants::Single` and `Variants::Multiple`
identically. This is incorrect for `Variants::Single` enums,
which delegate their layout to that of a variant with a particular
index (or no variant at all if the enum is empty).
This flaw manifested first as an ICE. `Tree::from_enum` attempted
to compute the tag of variants other than the one at
`Variants::Single`'s `index`, and fell afoul of a sanity-checking
assertion in `compiler/rustc_const_eval/src/interpret/discriminant.rs`.
This assertion is non-load-bearing, and can be removed; the routine
its in is well-behaved even without it.
With the assertion removed, the proximate issue becomes apparent:
calling `Tree::from_variant` on a variant that does not exist is
ill-defined. A sanity check the given variant has
`FieldShapes::Arbitrary` fails, and the analysis is (correctly)
aborted with `Err::NotYetSupported`.
This commit corrects this chain of failures by ensuring that
`Tree::from_variant` is not called on variants that are, as far as
layout is concerned, nonexistent. Specifically, the implementation
of `Tree::from_enum` is now partitioned into three cases:
1. enums that are uninhabited
2. enums for which all but one variant is uninhabited
3. enums with multiple inhabited variants
`Tree::from_variant` is now only invoked in the third case. In the
first case, `Tree::uninhabited()` is produced. In the second case,
the layout is delegated to `Variants::Single`'s index.
Fixes#125811
We implement the trait only for definitions that should have a type.
It's possible that I missed a few definitions, but we can add them later
if needed.
Extend SCC construction to enable extra functionality
Do YOU feel like your SCC construction doesn't do enough? Then I have a patch for you! SCCs can now do *everything*! Well, almost.
This patch has been extracted from #123720. It specifically enhances
`Sccs` to allow tracking arbitrary commutative properties (think min/max mappings on nodes vs arbitrary closures) of strongly connected components, including
- reachable values (max/min)
- SCC-internal values (max/min)
This helps with among other things universe computation. We can now identify
SCC universes as a reasonably straightforward "find max/min" operation during SCC construction. This is also included in this patch.
It's also more or less zero-cost; don't use the new features, don't pay for them.
This commit also vastly extends the documentation of the SCCs module, which I had a very hard time following. It may or may not have gotten easier to read for someone else.
I believe this logic can also be used in leak check, but haven't checked. Ha. ha. Ha.
