make generalization code create new variables in correct universe
In our type inference system, when we "generalize" a type T to become
a suitable value for a type variable V, we sometimes wind up creating
new inference variables. So, for example, if we are making V be some
subtype of `&'X u32`, then we might instantiate V with `&'Y u32`.
This generalized type is then related `&'Y u32 <: &'X u32`, resulting
in a region constriant `'Y: 'X`. Previously, however, we were making
these fresh variables like `'Y` in the "current universe", but they
should be created in the universe of V. Moreover, we sometimes cheat
in an invariant context and avoid creating fresh variables if we know
the result must be equal -- we can only do that when the universes
work out.
Fixes#57843
r? @pnkfelix
Add specific feature gate error for const-unstable features
Before:
```
error: `impl Trait` in const fn is unstable
--> src/lib.rs:7:19
|
7 | const fn foo() -> impl T {
| ^^^^^^
error: aborting due to previous error
```
After:
```
error[E0723]: `impl Trait` in const fn is unstable (see issue #57563)
--> src/lib.rs:7:19
|
7 | const fn foo() -> impl T {
| ^^^^^^
= help: add #![feature(const_fn)] to the crate attributes to enable
error: aborting due to previous error
```
This improves the situation with https://github.com/rust-lang/rust/issues/57563. Fixes https://github.com/rust-lang/rust/issues/57544. Fixes https://github.com/rust-lang/rust/issues/54469.
r? @oli-obk
In our type inference system, when we "generalize" a type T to become
a suitable value for a type variable V, we sometimes wind up creating
new inference variables. So, for example, if we are making V be some
subtype of `&'X u32`, then we might instantiate V with `&'Y u32`.
This generalized type is then related `&'Y u32 <: &'X u32`, resulting
in a region constriant `'Y: 'X`. Previously, however, we were making
these fresh variables like `'Y` in the "current universe", but they
should be created in the universe of V. Moreover, we sometimes cheat
in an invariant context and avoid creating fresh variables if we know
the result must be equal -- we can only do that when the universes
work out.
Hidden suggestion support
Add way to hide suggestion snippet window from cli output to avoid cluttered spans that don't enhance understanding.
r? @pietroalbini CC @zackmdavis
Tweak "incompatible match arms" error
- Point at the body expression of the match arm with the type error.
- Point at the prior match arms explicitly stating the evaluated type.
- Point at the entire match expr in a secondary span, instead of primary.
- For type errors in the first match arm, the cause is outside of the
match, treat as implicit block error to give a more appropriate error.
Fix#46776, fix#57206.
CC #24157, #38234.
Cosmetic improvements to doc comments
This has been factored out from https://github.com/rust-lang/rust/pull/58036 to only include changes to documentation comments (throughout the rustc codebase).
r? @steveklabnik
Once you're happy with this, maybe we could get it through with r=1, so it doesn't constantly get invalidated? (I'm not sure this will be an issue, but just in case...) Anyway, thanks for your advice so far!
Deduplicate mismatched delimiter errors
Delay unmatched delimiter errors until after the parser has run to deduplicate them when parsing and attempt recovering intelligently.
Second attempt at #54029, follow up to #53949. Fix#31528.
- Point at the body expression of the match arm with the type error.
- Point at the prior match arms explicitely stating the evaluated type.
- Point at the entire match expr in a secondary span, instead of primary.
- For type errors in the first match arm, the cause is outside of the
match, treat as implicit block error to give a more appropriate error.
Overhaul `syntax::fold::Folder`.
This PR changes `syntax::fold::Folder` from a functional style
(where most methods take a `T` and produce a new `T`) to a more
imperative style (where most methods take and modify a `&mut T`), and
renames it `syntax::mut_visit::MutVisitor`.
This makes the code faster and more concise.
This commit changes `syntax::fold::Folder` from a functional style
(where most methods take a `T` and produce a new `T`) to a more
imperative style (where most methods take and modify a `&mut T`), and
renames it `syntax::mut_visit::MutVisitor`.
The first benefit is speed. The functional style does not require any
reallocations, due to the use of `P::map` and
`MoveMap::move_{,flat_}map`. However, every field in the AST must be
overwritten; even those fields that are unchanged are overwritten with
the same value. This causes a lot of unnecessary memory writes. The
imperative style reduces instruction counts by 1--3% across a wide range
of workloads, particularly incremental workloads.
The second benefit is conciseness; the imperative style is usually more
concise. E.g. compare the old functional style:
```
fn fold_abc(&mut self, abc: ABC) {
ABC {
a: fold_a(abc.a),
b: fold_b(abc.b),
c: abc.c,
}
}
```
with the imperative style:
```
fn visit_abc(&mut self, ABC { a, b, c: _ }: &mut ABC) {
visit_a(a);
visit_b(b);
}
```
(The reductions get larger in more complex examples.)
Overall, the patch removes over 200 lines of code -- even though the new
code has more comments -- and a lot of the remaining lines have fewer
characters.
Some notes:
- The old style used methods called `fold_*`. The new style mostly uses
methods called `visit_*`, but there are a few methods that map a `T`
to something other than a `T`, which are called `flat_map_*` (`T` maps
to multiple `T`s) or `filter_map_*` (`T` maps to 0 or 1 `T`s).
- `move_map.rs`/`MoveMap`/`move_map`/`move_flat_map` are renamed
`map_in_place.rs`/`MapInPlace`/`map_in_place`/`flat_map_in_place` to
reflect their slightly changed signatures.
- Although this commit renames the `fold` module as `mut_visit`, it
keeps it in the `fold.rs` file, so as not to confuse git. The next
commit will rename the file.
Add suggestion for duplicated import.
Fixes#52891.
This PR adds a suggestion when a import is duplicated (ie. the same name
is used twice trying to import the same thing) to remove the second
import.
Currently, the target of a use statement will be updated with
the visibility of the use statement itself (if the use statement was
visible).
This commit ensures that if the path to the target item is via another
use statement then that intermediate use statement will also have the
visibility updated like the target. This silences incorrect
`unreachable_pub` lints with inactionable suggestions.
This commit adds a suggestion when a import is duplicated (ie. the same name
is used twice trying to import the same thing) to remove the second
import.
Add information to higher-ranked lifetimes conflicts error messages
Make these errors go through the new "placeholder error" code path, to have self tys displayed and make them hopefully less confusing.
Should fix#57362.
r? @nikomatsakis — so we can iterate on the specific wording you wanted.
add typo suggestion to unknown attribute error
Provides a suggestion using Levenshtein distance to suggest built-in attributes and attribute macros.
Fixes#49270.
This commit extends existing suggestions to prefix unused variable
bindings in match arms with an underscore so that it applies to all
patterns in a match arm.
When mentioning lifetimes, only invert wording between the expected trait and the self type when the self type has the vid.
This way, the lifetimes always stay close to the self type or trait ref that actually contains them.
Suggest removing leading left angle brackets.
Fixes#57819.
This PR adds errors and accompanying suggestions as below:
```
bar::<<<<<T as Foo>::Output>();
^^^ help: remove extra angle brackets
```
r? @estebank
[NLL] Clean up handling of type annotations
* Renames (Canonical)?UserTypeAnnotation -> (Canonical)?UserType so that the name CanonicalUserTypeAnnotation is free.
* Keep the inferred type associated to user type annotations in the MIR, so that it can be compared against the annotated type, even when the annotated expression gets removed from the MIR. (#54943)
* Use the inferred type to allow infallible handling of user type projections (#57531)
* Uses revisions for the tests in #56993
* Check the types of `Unevaluated` constants with no annotations (#46702)
* Some drive-by cleanup
Closes#46702Closes#54943Closes#57531Closes#57731
cc #56993 leaving this open to track the underlying issue: we are not running tests with full NLL enabled on CI at the moment
r? @nikomatsakis
