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3540 Commits

Author SHA1 Message Date
Nilstrieb
ddf7982741 Remove benches from rustc_middle 
These benches benchmark rust langauge features and not the compiler,
so they seem to be in the wrong place here. They also all take <1ns,
making them pretty useless. Looking at their git history, they just
seem to have been carried around for many, many years. This commit
ends their journey.
 2022-09-25 18:35:43 +02:00
bors
d0ece44cfa Auto merge of #102040 - TaKO8Ki:separate-definitions-and-hir-owners, r=cjgillot 
Separate definitions and HIR owners in the type system

Fixes #83158

r? `@cjgillot`
 2022-09-24 22:42:07 +00:00
Takayuki Maeda
8fe936099a separate definitions and HIR owners 
fix a ui test

use `into`

fix clippy ui test

fix a run-make-fulldeps test

implement `IntoQueryParam<DefId>` for `OwnerId`

use `OwnerId` for more queries

change the type of `ParentOwnerIterator::Item` to `(OwnerId, OwnerNode)`
 2022-09-24 23:21:19 +09:00
Matthias Krüger
bf167e0ae5
Rollup merge of #102088 - oli-obk:cleanups, r=bjorn3 
Fix wrongly refactored Lift impl

see https://github.com/rust-lang/rust/pull/101858#issuecomment-1252713639

r? ``@bjorn3``
 2022-09-24 14:29:53 +02:00
bors
bb5a016175 Auto merge of #102064 - cjgillot:revert, r=Mark-Simulacrum 
Revert perf-regression 101620

Reverts #101862 #101620

r? `@Mark-Simulacrum`
 2022-09-24 09:36:29 +00:00
Matthias Krüger
a842357d37
Rollup merge of #102152 - compiler-errors:issue-102140, r=fee1-dead 
Calculate `ProjectionTy::trait_def_id` for return-position `impl Trait` in trait correctly

Fixes #102140
 2022-09-24 07:38:56 +02:00
bors
e1c28e0c85 Auto merge of #102068 - cjgillot:erased-lifetime-print, r=eholk 
Always print '_, even for erased lifetimes.

Explicit lifetime arguments are now the recommended syntax in rust 2018 and rust 2021.  This PR applies this discipline to rustc itself.
 2022-09-24 01:23:17 +00:00
Camille GILLOT
aac2c7ddd8 Always print '_, even for erased lifetimes. 2022-09-23 18:42:14 +02:00
bors
9a963e3bad Auto merge of #102056 - b-naber:unevaluated, r=lcnr 
Introduce mir::Unevaluated

Previously the distinction between unevaluated constants in the type-system and in mir was not explicit and a little confusing. Probably better to introduce its own type for that.

r? `@lcnr`
 2022-09-23 13:39:11 +00:00
b-naber
a705e65605 rename Unevaluated to UnevaluatedConst 2022-09-23 14:27:34 +02:00
bors
4d44e09cb1 Auto merge of #102165 - matthiaskrgr:rollup-n5oquhe, r=matthiaskrgr 
Rollup of 8 pull requests

Successful merges:

 - #100734 (Split out async_fn_in_trait into a separate feature)
 - #101664 (Note if mismatched types have a similar name)
 - #101815 (Migrated the rustc_passes annotation without effect diagnostic infrastructure)
 - #102042 (Distribute rust-docs-json via rustup.)
 - #102066 (rustdoc: remove unnecessary `max-width` on headers)
 - #102095 (Deduplicate two functions that would soon have been three)
 - #102104 (Set 'exec-env:RUST_BACKTRACE=0' in const-eval-select tests)
 - #102112 (Allow full relro on powerpc64-unknown-linux-gnu)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
 2022-09-23 09:33:23 +00:00
Matthias Krüger
c2d2535b84
Rollup merge of #101664 - mejrs:similarity, r=fee1-dead 
Note if mismatched types have a similar name

If users get a type error between similarly named types, it will point out that these are actually different types, and where they were defined.
 2022-09-23 04:29:16 +02:00
Michael Goulet
79c665b2a3 Calculate ProjectionTy::trait_def_id correctly 2022-09-22 19:49:18 +00:00
Matthias Krüger
aa384834d7
Rollup merge of #102133 - b-naber:use-valtrees-in-fast-reject, r=lcnr 
Use valtrees for comparison

r? `@lcnr`
 2022-09-22 21:34:54 +02:00
Matthias Krüger
b93c9a7d37
Rollup merge of #102128 - oli-obk:const_unification, r=lcnr 
Const unification is already infallible, remove the error handling logic

r? `@lcnr`

is this expected to be used in the future? Right now it is dead code.
 2022-09-22 21:34:53 +02:00
Camille GILLOT
fc43df0333 Revert "Auto merge of #101620 - cjgillot:compute_lint_levels_by_def, r=oli-obk" 
This reverts commit 2cb9a65684, reversing
changes made to 750bd1a7ff.
 2022-09-22 19:36:11 +02:00
Camille GILLOT
381bd2a836 Revert "Auto merge of #101862 - cjgillot:lint-regression, r=oli-obk" 
This reverts commit bc7b17cfe3, reversing
changes made to 5253b0a0a1.
 2022-09-22 19:34:01 +02:00
b-naber
e8594257f6 use valtrees for comparison 2022-09-22 13:10:53 +02:00
b-naber
efb908991b address review 2022-09-22 12:35:29 +02:00
b-naber
9f3784df89 introduce mir::Unevaluated 2022-09-22 12:35:28 +02:00
Oli Scherer
13438ee29c Const unification is already infallible, remove the error handling logic 2022-09-22 08:20:13 +00:00
bors
7a8636c843 Auto merge of #100982 - fee1-dead-contrib:const-impl-requires-const-trait, r=oli-obk 
Require `#[const_trait]` on `Trait` for `impl const Trait`

r? `@oli-obk`
 2022-09-22 04:22:24 +00:00
Jhonny Bill Mena
e52e2344dc FIX - adopt new Diagnostic naming in newly migrated modules 
FIX - ambiguous Diagnostic link in docs

UPDATE - rename diagnostic_items to IntoDiagnostic and AddToDiagnostic

[Gardening] FIX - formatting via `x fmt`

FIX - rebase conflicts. NOTE: Confirm wheather or not we want to handle TargetDataLayoutErrorsWrapper this way

DELETE - unneeded allow attributes in Handler method

FIX - broken test

FIX - Rebase conflict

UPDATE - rename residual _SessionDiagnostic and fix LintDiag link
 2022-09-21 11:43:22 -04:00
Jhonny Bill Mena
5f91719f75 UPDATE - rename SessionSubdiagnostic macro to Subdiagnostic 
Also renames:
- sym::AddSubdiagnostic to sym:: Subdiagnostic
- rustc_diagnostic_item = "AddSubdiagnostic" to rustc_diagnostic_item = "Subdiagnostic"
 2022-09-21 11:39:53 -04:00
Jhonny Bill Mena
a3396b2070 UPDATE - rename DiagnosticHandler macro to Diagnostic 2022-09-21 11:39:53 -04:00
Jhonny Bill Mena
19b348fed4 UPDATE - rename DiagnosticHandler trait to IntoDiagnostic 2022-09-21 11:39:52 -04:00
Oli Scherer
3e6c9e5a19 Fix wrongly refactored Lift impl 2022-09-21 08:29:19 +00:00
bors
432abd86f2 Auto merge of #102061 - notriddle:rollup-kwu9vp8, r=notriddle 
Rollup of 12 pull requests

Successful merges:

 - #100250 (Manually cleanup token stream when macro expansion aborts.)
 - #101014 (Fix -Zmeta-stats ICE by giving `FileEncoder` file read permissions)
 - #101958 (Improve error for when query is unsupported by crate)
 - #101976 (MirPhase: clarify that linting is not a semantic change)
 - #102001 (Use LLVM C-API to build atomic cmpxchg and fence)
 - #102008 (Add GUI test for notable traits element position)
 - #102013 (Simplify rpitit handling on lower_fn_decl)
 - #102021 (some post-valtree cleanup)
 - #102027 (rustdoc: remove `docblock` class from `item-decl`)
 - #102034 (rustdoc: remove no-op CSS `h1-6 { border-bottom-color }`)
 - #102038 (Make the `normalize-overflow` rustdoc test actually do something)
 - #102053 (⬆️ rust-analyzer)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
 2022-09-20 19:10:11 +00:00
Michael Howell
b149c48186
Rollup merge of #102021 - lcnr:tyConst-fun, r=b-naber,BoxyUwU 
some post-valtree cleanup

r? project-const-generics cc ```@b-naber```
 2022-09-20 10:13:01 -07:00
Michael Howell
0d2e57cb04
Rollup merge of #101976 - RalfJung:mir-semantic-phases, r=oli-obk 
MirPhase: clarify that linting is not a semantic change

r? ```@JakobDegen```
 2022-09-20 10:12:58 -07:00
Michael Howell
2c893737a6
Rollup merge of #101958 - hanar3:101666/enhance-error-message, r=oli-obk 
Improve error for when query is unsupported by crate

This is an improvement to the error message mentioned on #101666.  It seems like a good idea to also add [this link to the rustc-dev-guide](https://rustc-dev-guide.rust-lang.org/query.html), if explaining the query system in detail is a concern here, but I'm unsure if there is any restrictions on adding links to error messages.
 2022-09-20 10:12:58 -07:00
bors
cd8cc91045 Auto merge of #101989 - fee1-dead-contrib:const_trait_impl-assoc-caller-bounds, r=oli-obk 
make projection bounds with const bounds satisfy const

Fixes #101982.
 2022-09-20 16:24:36 +00:00
bors
4136b59b7d Auto merge of #99806 - oli-obk:unconstrained_opaque_type, r=estebank 
Allow patterns to constrain the hidden type of opaque types

fixes #96572

reverts a revert as original PR was a perf regression that was fixed by reverting it: https://github.com/rust-lang/rust/pull/99368#issuecomment-1186587864)

TODO:

* check if https://github.com/rust-lang/rust/issues/99685 is avoided
 2022-09-20 12:09:52 +00:00
Matthias Krüger
7697a244cc
Rollup merge of #101881 - TaKO8Ki:remove-unused-struct-field, r=sanxiyn 
Remove an unused struct field `late_bound`
 2022-09-19 17:55:19 +02:00
mejrs
c65866000e Incorporate feedback 2022-09-19 17:19:45 +02:00
lcnr
c54c5a3c77 DestructuredConst split mir and ty 2022-09-19 17:00:38 +02:00
lcnr
638b612154 remove ty::Const::from_inline_const 2022-09-19 16:10:18 +02:00
lcnr
0c3e01d8f6 extend polymorphization hack comment. 2022-09-19 11:44:29 +02:00
lcnr
647052fc04 remove the Subst trait, always use EarlyBinder 2022-09-19 11:37:27 +02:00
lcnr
d398b54de6 do not implement type traversal for EarlyBinder 2022-09-19 11:28:32 +02:00
bors
efa717bc2d Auto merge of #101924 - jackh726:revert-static-hrtb-error, r=compiler-errors 
Re-add HRTB implied static bug note

r? `@compiler-errors` since you reviewed it previously

I deleted a `normalize` call and forgot about it. Whoops.
 2022-09-19 04:56:14 +00:00
Deadbeef
ee96ae0a32 make projection bounds with const bounds satisfy const 2022-09-18 18:05:30 +00:00
Ralf Jung
eed6fdb0eb clarify that linting is not a semantic change 2022-09-18 14:14:42 +02:00
bors
bc7b17cfe3 Auto merge of #101862 - cjgillot:lint-regression, r=oli-obk 
Do not fetch HIR node when iterating to find lint.

Addresses the regression in https://github.com/rust-lang/rust/pull/101620
 2022-09-18 00:46:14 +00:00
hanar3
0405a5d4e9 improve error message for when a query isn't supported 2022-09-17 20:25:37 -03:00
Matthias Krüger
a6b34cd928
Rollup merge of #101713 - Bryanskiy:AccessLevels, r=petrochenkov 
change AccessLevels representation

Part of RFC (https://github.com/rust-lang/rust/issues/48054). This patch implements effective visibility table with basic methods and change AccessLevels table representation according to it.

r? ``@petrochenkov``
 2022-09-17 23:30:49 +02:00
bors
48de123d7a Auto merge of #101857 - lcnr:make-dyn-again, r=jackh726 
change `FnMutDelegate` to trait objects

cc #100016 as mentioned in the last t-compiler meeting

r? `@jackh726`
 2022-09-17 13:37:48 +00:00
Dylan DPC
3ad81e0dd8
Rollup merge of #93628 - est31:stabilize_let_else, r=joshtriplett 
Stabilize `let else`

🎉  **Stabilizes the `let else` feature, added by [RFC 3137](https://github.com/rust-lang/rfcs/pull/3137).** 🎉

Reference PR: https://github.com/rust-lang/reference/pull/1156

closes #87335 (`let else` tracking issue)

FCP: https://github.com/rust-lang/rust/pull/93628#issuecomment-1029383585

----------

## Stabilization report

### Summary

The feature allows refutable patterns in `let` statements if the expression is
followed by a diverging `else`:

```Rust
fn get_count_item(s: &str) -> (u64, &str) {
    let mut it = s.split(' ');
    let (Some(count_str), Some(item)) = (it.next(), it.next()) else {
        panic!("Can't segment count item pair: '{s}'");
    };
    let Ok(count) = u64::from_str(count_str) else {
        panic!("Can't parse integer: '{count_str}'");
    };
    (count, item)
}
assert_eq!(get_count_item("3 chairs"), (3, "chairs"));
```

### Differences from the RFC / Desugaring

Outside of desugaring I'm not aware of any differences between the implementation and the RFC. The chosen desugaring has been changed from the RFC's [original](https://rust-lang.github.io/rfcs/3137-let-else.html#reference-level-explanations). You can read a detailed discussion of the implementation history of it in `@cormacrelf` 's [summary](https://github.com/rust-lang/rust/pull/93628#issuecomment-1041143670) in this thread, as well as the [followup](https://github.com/rust-lang/rust/pull/93628#issuecomment-1046598419). Since that followup, further changes have happened to the desugaring, in #98574, #99518, #99954. The later changes were mostly about the drop order: On match, temporaries drop in the same order as they would for a `let` declaration. On mismatch, temporaries drop before the `else` block.

### Test cases

In chronological order as they were merged.

Added by df9a2e0687 (#87688):

* [`ui/pattern/usefulness/top-level-alternation.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/pattern/usefulness/top-level-alternation.rs) to ensure the unreachable pattern lint visits patterns inside `let else`.

Added by 5b95df4bdc (#87688):

* [`ui/let-else/let-else-bool-binop-init.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/let-else-bool-binop-init.rs) to ensure that no lazy boolean expressions (using `&&` or `||`) are allowed in the expression, as the RFC mandates.
* [`ui/let-else/let-else-brace-before-else.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/let-else-brace-before-else.rs) to ensure that no `}` directly preceding the `else` is allowed in the expression, as the RFC mandates.
* [`ui/let-else/let-else-check.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/let-else-check.rs) to ensure that `#[allow(...)]` attributes added to the entire `let` statement apply for the `else` block.
* [`ui/let-else/let-else-irrefutable.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/let-else-irrefutable.rs) to ensure that the `irrefutable_let_patterns` lint fires.
* [`ui/let-else/let-else-missing-semicolon.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/let-else-missing-semicolon.rs) to ensure the presence of semicolons at the end of the `let` statement.
* [`ui/let-else/let-else-non-diverging.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/let-else-non-diverging.rs) to ensure the `else` block diverges.
* [`ui/let-else/let-else-run-pass.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/let-else-run-pass.rs) to ensure the feature works in some simple test case settings.
* [`ui/let-else/let-else-scope.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/let-else-scope.rs) to ensure the bindings created by the outer `let` expression are not available in the `else` block of it.

Added by bf7c32a447 (#89965):

* [`ui/let-else/issue-89960.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/issue-89960.rs) as a regression test for the ICE-on-error bug #89960 . Later in 102b9125e1 this got removed in favour of more comprehensive tests.

Added by 856541963c (#89974):

* [`ui/let-else/let-else-if.rs`](https://github.com/rust-lang/rust/blob/1.58.1/src/test/ui/let-else/let-else-if.rs) to test for the improved error message that points out that `let else if` is not possible.

Added by 9b45713b6c:

* [`ui/let-else/let-else-allow-unused.rs`](https://github.com/rust-lang/rust/blob/1.61.0/src/test/ui/let-else/let-else-allow-unused.rs) as a regression test for #89807, to ensure that `#[allow(...)]` attributes added to the entire `let` statement apply for bindings created by the `let else` pattern.

Added by 61bcd8d307 (#89841):

* [`ui/let-else/let-else-non-copy.rs`](https://github.com/rust-lang/rust/blob/1.61.0/src/test/ui/let-else/let-else-non-copy.rs) to ensure that a copy is performed out of non-copy wrapper types. This mirrors `if let` behaviour. The test case bases on rustc internal changes originally meant for #89933 but then removed from the PR due to the error prior to the improvements of #89841.
* [`ui/let-else/let-else-source-expr-nomove-pass.rs `](https://github.com/rust-lang/rust/blob/1.61.0/src/test/ui/let-else/let-else-source-expr-nomove-pass.rs) to ensure that while there is a move of the binding in the successful case, the `else` case can still access the non-matching value. This mirrors `if let` behaviour.

Added by 102b9125e1 (#89841):

* [`ui/let-else/let-else-ref-bindings.rs`](https://github.com/rust-lang/rust/blob/1.61.0/src/test/ui/let-else/let-else-ref-bindings.rs) and [`ui/let-else/let-else-ref-bindings-pass.rs `](https://github.com/rust-lang/rust/blob/1.61.0/src/test/ui/let-else/let-else-ref-bindings-pass.rs) to check `ref` and `ref mut` keywords in the pattern work correctly and error when needed.

Added by 2715c5f984 (#89841):

* Match ergonomic tests adapted from the `rfc2005` test suite.

Added by fec8a507a2 (#89841):

* [`ui/let-else/let-else-deref-coercion-annotated.rs`](https://github.com/rust-lang/rust/blob/1.61.0/src/test/ui/let-else/let-else-deref-coercion-annotated.rs) and [`ui/let-else/let-else-deref-coercion.rs`](https://github.com/rust-lang/rust/blob/1.61.0/src/test/ui/let-else/let-else-deref-coercion.rs) to check deref coercions.

#### Added since this stabilization report was originally written (2022-02-09)

Added by 76ea566677 (#94211):

* [`ui/let-else/let-else-destructuring.rs`](https://github.com/rust-lang/rust/blob/1.63.0/src/test/ui/let-else/let-else-destructuring.rs) to give a nice error message if an user tries to do an assignment with a (possibly refutable) pattern and an `else` block, like asked for in #93995.

Added by e7730dcb7e (#94208):

* [`ui/let-else/let-else-allow-in-expr.rs`](https://github.com/rust-lang/rust/blob/1.61.0/src/test/ui/let-else/let-else-allow-in-expr.rs) to test whether `#[allow(unused_variables)]` works in the expr, as well as its non presence, as well as putting it on the entire `let else` *affects* the expr, too. This was adding a missing test as pointed out by the stabilization report.
* Expansion of `ui/let-else/let-else-allow-unused.rs` and `ui/let-else/let-else-check.rs` to ensure that non-presence of `#[allow(unused)]` does issue the unused lint. This was adding a missing test case as pointed out by the stabilization report.

Added by 5bd71063b3 (#94208):

* [`ui/let-else/let-else-slicing-error.rs`](https://github.com/rust-lang/rust/blob/1.61.0/src/test/ui/let-else/let-else-slicing-error.rs), a regression test for #92069, which got fixed without addition of a regression test. This resolves a missing test as pointed out by the stabilization report.

Added by 5374688e1d (#98574):

* [`src/test/ui/async-await/async-await-let-else.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui/async-await/async-await-let-else.rs) to test the interaction of async/await with `let else`

Added by 6c529ded86 (#98574):

* [`src/test/ui/let-else/let-else-temporary-lifetime.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui/let-else/let-else-temporary-lifetime.rs) as a (partial) regression test for #98672

Added by 9b56640106 (#99518):

* [`src/test/ui/let-else/let-else-temp-borrowck.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui/let-else/let-else-temporary-lifetime.rs) as a regression test for #93951
* Extension of `src/test/ui/let-else/let-else-temporary-lifetime.rs` to include a partial regression test for #98672 (especially regarding `else` drop order)

Added by baf9a7cb57 (#99518):

* Extension of `src/test/ui/let-else/let-else-temporary-lifetime.rs` to include a partial regression test for #93951, similar to `let-else-temp-borrowck.rs`

Added by 60be2de8b7 (#99518):

* Extension of `src/test/ui/let-else/let-else-temporary-lifetime.rs` to include a program that can now be compiled thanks to borrow checker implications of #99518

Added by 47a7a91c96 (#100132):

* [`src/test/ui/let-else/issue-100103.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui/let-else/issue-100103.rs), as a regression test for #100103, to ensure that there is no ICE when doing `Err(...)?` inside else blocks.

Added by e3c5bd617d (#100443):

* [`src/test/ui/let-else/let-else-then-diverge.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui/let-else/let-else-then-diverge.rs), to verify that there is no unreachable code error with the current desugaring.

Added by 981852677c (#100443):

* [`src/test/ui/let-else/issue-94176.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui/let-else/issue-94176.rs), to make sure that a correct span is emitted for a missing trailing expression error. Regression test for #94176.

Added by e182d12a84 (#100434):

* [src/test/ui/unpretty/pretty-let-else.rs](https://github.com/rust-lang/rust/blob/master/src/test/ui/unpretty/pretty-let-else.rs), as a regression test to ensure pretty printing works for `let else` (this bug surfaced in many different ways)

Added by e26285603c (#99954):

* [`src/test/ui/let-else/let-else-temporary-lifetime.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui/let-else/let-else-temporary-lifetime.rs) extended to contain & borrows as well, as this was identified as an earlier issue with the desugaring: https://github.com/rust-lang/rust/issues/98672#issuecomment-1200196921

Added by 2d8460ef43 (#99291):

* [`src/test/ui/let-else/let-else-drop-order.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui/let-else/let-else-drop-order.rs) a matrix based test for various drop order behaviour of `let else`. Especially, it verifies equality of `let` and `let else` drop orders, [resolving](https://github.com/rust-lang/rust/pull/93628#issuecomment-1238498468) a [stabilization blocker](https://github.com/rust-lang/rust/pull/93628#issuecomment-1055738523).

Added by 1b87ce0d40 (#101410):

* Edit to `src/test/ui/let-else/let-else-temporary-lifetime.rs` to add the `-Zvalidate-mir` flag, as a regression test for #99228

Added by af591ebe4d (#101410):

* [`src/test/ui/let-else/issue-99975.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui/let-else/issue-99975.rs) as a regression test for the ICE #99975.

Added by this PR:

* `ui/let-else/let-else.rs`, a simple run-pass check, similar to `ui/let-else/let-else-run-pass.rs`.

### Things not currently tested

* ~~The `#[allow(...)]` tests check whether allow works, but they don't check whether the non-presence of allow causes a lint to fire.~~ → *test added by e7730dcb7eb29a10ee73f269f4dc6e9d606db0da*
* ~~There is no `#[allow(...)]` test for the expression, as there are tests for the pattern and the else block.~~ → *test added by e7730dcb7eb29a10ee73f269f4dc6e9d606db0da*
* ~~`let-else-brace-before-else.rs` forbids the `let ... = {} else {}` pattern and there is a rustfix to obtain `let ... = ({}) else {}`. I'm not sure whether the `.fixed` files are checked by the tooling that they compile. But if there is no such check, it would be neat to make sure that `let ... = ({}) else {}` compiles.~~ → *test added by e7730dcb7eb29a10ee73f269f4dc6e9d606db0da*
* ~~#92069 got closed as fixed, but no regression test was added. Not sure it's worth to add one.~~ → *test added by 5bd71063b3810d977aa376d1e6dd7cec359330cc*
* ~~consistency between `let else` and `if let` regarding lifetimes and drop order: https://github.com/rust-lang/rust/pull/93628#issuecomment-1055738523~~ → *test added by 2d8460ef43d902f34ba2133fe38f66ee8d2fdafc*

Edit: they are all tested now.

### Possible future work / Refutable destructuring assignments

[RFC 2909](https://rust-lang.github.io/rfcs/2909-destructuring-assignment.html) specifies destructuring assignment, allowing statements like `FooBar { a, b, c } = foo();`.
As it was stabilized, destructuring assignment only allows *irrefutable* patterns, which before the advent of `let else` were the only patterns that `let` supported.
So the combination of `let else` and destructuring assignments gives reason to think about extensions of the destructuring assignments feature that allow refutable patterns, discussed in #93995.

A naive mapping of `let else` to destructuring assignments in the form of `Some(v) = foo() else { ... };` might not be the ideal way. `let else` needs a diverging `else` clause as it introduces new bindings, while assignments have a default behaviour to fall back to if the pattern does not match, in the form of not performing the assignment. Thus, there is no good case to require divergence, or even an `else` clause at all, beyond the need for having *some* introducer syntax so that it is clear to readers that the assignment is not a given (enums and structs look similar). There are better candidates for introducer syntax however than an empty `else {}` clause, like `maybe` which could be added as a keyword on an edition boundary:

```Rust
let mut v = 0;
maybe Some(v) = foo(&v);
maybe Some(v) = foo(&v) else { bar() };
```

Further design discussion is left to an RFC, or the linked issue.
 2022-09-17 15:31:06 +05:30
bors
c524c7dd25 Auto merge of #98588 - b-naber:valtrees-cleanup, r=lcnr 
Use only ty::Unevaluated<'tcx, ()> in type system

r? `@lcnr`
 2022-09-17 03:04:22 +00:00
Jack Huey
9929c0ac76 Add AscribeUserTypeProvePredicate 2022-09-16 17:20:11 -04:00