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733 Commits

Author SHA1 Message Date
Michael Goulet
6e6fe30d0f Comment why normalization is needed for debug assertions 2022-10-23 17:23:35 +00:00
Nilstrieb
c65ebae221
Migrate all diagnostics 2022-10-23 10:09:44 +02:00
Matthias Krüger
801e32647e
Rollup merge of #103315 - RalfJung:interpret-switchint-ice, r=bjorn3 
interpret: remove an incorrect assertion

This fixes an ICE in Miri, [reported](https://rust-lang.zulipchat.com/#narrow/stream/269128-miri/topic/SwitchInt.20with.20no.20targets.3F) by `@saethlin.` The faulty assertion was introduced by 432535da2b, when a previously correct assertion checking that the `otherwise` target exists got replaced by this assertion checking that at least one more target beyond `otherwise` exists.

Sadly we don't have a small reproducer so I don't think we can easily add a testcase.
 2022-10-20 22:42:41 +02:00
Ralf Jung
bf14e3196b interpret: remove an incorrect assertion 2022-10-20 19:06:34 +02:00
Gimgim
49f34bd814
Surround type with backticks 2022-10-15 15:28:29 +05:30
Dylan DPC
77064b7f0a
Rollup merge of #103018 - Rageking8:more-dupe-word-typos, r=TaKO8Ki 
More dupe word typos

I only picked those changes (from the regex search) that I am pretty certain doesn't change meaning and is just a typo fix. Do correct me if any fix is undesirable and I can revert those. Thanks.
 2022-10-14 16:19:15 +05:30
Rageking8
7122abaddf more dupe word typos 2022-10-14 12:57:56 +08:00
Michael Goulet
af3c6f9a03 Delay intrinsic call until after we've determined the callee is a function 2022-10-13 03:10:00 +00:00
Dylan DPC
c763ebc72f
Rollup merge of #102830 - compiler-errors:constness-parity, r=fee1-dead 
Unify `tcx.constness` query and param env constness checks

The checks that we do in the `constness` query seem inconsistent with the checks that we do to determine if an item's param-env is const, so I merged them into the `constness` query and call that from the `param_env` query.

I'm not sure if this totally makes sense -- is there a case where `tcx.param_env()` would return a const param-env for an item whose `tcx.constness()` is `Constness::NotConst`? Because if not, it seems a bit dangerous that these two differ.

Luckily, not many places actually use `tcx.constness()`, and the checks in `tcx.param_env()` seem stricter than the checks in `tcx.constness()` (at least for the types of items we type-check).

Also, due to the way that `tcx.param_env()` is implemented, it _never_ used to return a const param-env for a item coming from a different crate, which also seems dangerous (though also probably not weaponizable currently, because we seldom actually compute the param-env for a non-local item).
 2022-10-12 22:13:25 +05:30
Nilstrieb
7bfef19844 Use tidy-alphabetical in the compiler 2022-10-12 17:49:10 +05:30
Michael Goulet
c646c4d403 Unify tcx.constness and param env constness checks 2022-10-12 04:04:09 +00:00
Matthias Krüger
c731646d6a
Rollup merge of #102675 - ouz-a:mir-technical-debt, r=oli-obk 
Remove `mir::CastKind::Misc`

As discussed in #97649 `mir::CastKind::Misc` is not clear, this PR addresses that by creating a new enum variant for every valid cast.

r? ````@oli-obk````
 2022-10-08 14:38:18 +02:00
bors
8b0c05d9ad Auto merge of #102091 - RalfJung:const_err, r=oli-obk 
make const_err a hard error

This lint has been deny-by-default with future incompat wording since [Rust 1.51](https://github.com/rust-lang/rust/pull/80394) and the stable release of this week starts showing it in cargo's future compat reports. I can't wait to finally get rid of at least some of the mess in our const-err-reporting-code. ;)

r? `@oli-obk`
Fixes https://github.com/rust-lang/rust/issues/71800
Fixes https://github.com/rust-lang/rust/issues/100114
 2022-10-07 20:50:51 +00:00
Ralf Jung
fd59d44f58 make const_err a hard error 2022-10-07 18:08:49 +02:00
Cameron Steffen
283abbf0e7 Change InferCtxtBuilder from enter to build 2022-10-07 07:10:40 -05:00
Cameron Steffen
4a68373217 Introduce TypeErrCtxt 
TypeErrCtxt optionally has a TypeckResults so that InferCtxt doesn't
need to.
 2022-10-07 07:06:16 -05:00
ouz-a
d59c7ff000 Remove mir::CastKind::Misc 2022-10-06 15:32:41 +03:00
bors
0152393048 Auto merge of #99324 - reez12g:issue-99144, r=jyn514 
Enable doctests in compiler/ crates

Helps with https://github.com/rust-lang/rust/issues/99144
 2022-10-06 03:01:57 +00:00
Ralf Jung
a0131f0a36 change might_permit_raw_init to fully detect LLVM UB, but not more than that 2022-10-05 09:22:50 +02:00
Dylan DPC
32dde232d8
Rollup merge of #102559 - compiler-errors:issue-102553, r=oli-obk 
Don't ICE when trying to copy unsized value in const prop

When we have a trivially false where-clause predicate like `Self: Sized` where `Self = dyn Trait`, we sometimes don't throw an error during typeck for an illegal operation such as copying an unsized type.

This, unfortunately, cannot be made into an error (at least not without some migration -- see #95611 for example), but we should at least not ICE, since this function will never actually be reachable from main, for example.

r? `@RalfJung` since I think you added these assertions? but feel free to reassign.

Fixes #102553
 2022-10-04 16:11:02 +05:30
Michael Goulet
c7d1ec009c Don't ICE when trying to copy unsized value in const prop 2022-10-02 19:21:06 +00:00
Cameron Steffen
4f12de0660 Change feature name to is_some_and 2022-10-01 11:45:52 -05:00
Maybe Waffle
a8f7e244b7 Refactor rustc lint API 2022-10-01 10:03:06 +00:00
reez12g
00612e23cb Mark ignore(illustrative) on docs in compiler/rustc_const_eval/src/interpret/validity.rs 2022-09-29 16:49:23 +09:00
reez12g
9a4c5abe45 Remove from compiler/ crates 2022-09-29 16:49:04 +09:00
Pietro Albini
3975d55d98
remove cfg(bootstrap) 2022-09-26 10:14:45 +02:00
fee1-dead
b7d9de72ac
Rollup merge of #102194 - fee1-dead-contrib:improve-const-drop, r=oli-obk 
Note the type when unable to drop values in compile time
 2022-09-25 22:06:39 +08:00
Deadbeef
2ce1cd511f Note the type when unable to drop values in compile time 2022-09-24 20:32:51 +00:00
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
Matthias Krüger
41ad726110
Rollup merge of #102113 - RalfJung:opty-assert-mem, r=oli-obk 
OpTy: fix a method taking self rather than &self

r? `@oli-obk`
 2022-09-22 21:34:49 +02:00
b-naber
9f3784df89 introduce mir::Unevaluated 2022-09-22 12:35:28 +02:00
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
Ralf Jung
0f4d7b6de8 OpTy: fix a method taking self rather than &self 2022-09-21 22:20:40 +02:00
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
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
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
8c0f8a285f
Rollup merge of #101985 - RalfJung:generate_stacktrace, r=oli-obk 
interpret: expose generate_stacktrace without full InterpCx

In Miri we sometimes want to emit diagnostics without having a full `&InterpCx` available. To avoid duplicating code, this adds a way to get a stacktrace from an arbitrary slice of interpreter frames, that Miri can use with access to just a thread manager.
 2022-09-19 17:55:21 +02:00
lcnr
c54c5a3c77 DestructuredConst split mir and ty 2022-09-19 17:00:38 +02:00
lcnr
526856768d ctfe, const_to_op only for mir constants 2022-09-19 16:17:33 +02:00
lcnr
647052fc04 remove the Subst trait, always use EarlyBinder 2022-09-19 11:37:27 +02:00
Ralf Jung
9fa3171015 interpret: expose generate_stacktrace without full InterpCx 2022-09-18 20:51:04 +02:00
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 df9a2e0687895731e12f4a2651e8d70acd08872d (#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 5b95df4bdc330f34213812ad65cae86ced90d80c (#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 bf7c32a4477a76bfd18fdcd8f45a939cbed82d34 (#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 102b9125e1cefbb8ed8408d2db3f9f7d5afddbf0 this got removed in favour of more comprehensive tests.

Added by 856541963ce95ef4f7d4a81784bb5002ccf63c93 (#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 9b45713b6c1775f0103a1ebee6ab7c6d9b781a21:

* [`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 61bcd8d3075471b3867428788c49f54fffe53f52 (#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 102b9125e1cefbb8ed8408d2db3f9f7d5afddbf0 (#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 2715c5f984fda7faa156d1c9cf91aa4934f0e00f (#89841):

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

Added by fec8a507a27de1b08a0b95592dc8ec93bf0a321a (#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 76ea56667703ac06689ff1d6fba5d170fa7392a7 (#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 e7730dcb7eb29a10ee73f269f4dc6e9d606db0da (#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 5bd71063b3810d977aa376d1e6dd7cec359330cc (#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 5374688e1d8cbcff7d1d14bb34e38fe6fe7c233e (#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 6c529ded8674b89c46052da92399227c3b764c6a (#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 9b566401068cb8450912f6ab48f3d0e60f5cb482 (#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 baf9a7cb57120ec1411196214fd0d1c33fb18bf6 (#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 60be2de8b7b8a1c4eee7e065b8cef38ea629a6a3 (#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 47a7a91c969ed2edd12c674ca05c1baf867f6f6f (#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 e3c5bd617d040b5ee0bc79e6e7f01772adce791b (#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 981852677c531d52f701b870bb27b45668a44d52 (#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 e182d12a8493b40a557394325a3a713b6528de60 (#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 e26285603ca8b83b9d06e56f74e10e3d410553ff (#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 2d8460ef43d902f34ba2133fe38f66ee8d2fdafc (#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 1b87ce0d4092045728c1c68282769d555706f273 (#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 af591ebe4d0cf2097a5fdc0bb710442d0f2e7876 (#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
Oli Scherer
40e2de8c41 Revert "Revert "Rollup merge of #98582 - oli-obk:unconstrained_opaque_type, r=estebank"" 
This reverts commit 4a742a691e7dd2522bad68b86fe2fd5a199d5561.
 2022-09-16 11:36:39 +00:00
Deadbeef
f8813cf10e do const trait method bounds check later in rustc_const_eval 2022-09-16 11:48:43 +08:00
est31
173eb6f407 Only enable the let_else feature on bootstrap 
On later stages, the feature is already stable.

Result of running:

rg -l "feature.let_else" compiler/ src/librustdoc/ library/ | xargs sed -s -i "s#\\[feature.let_else#\\[cfg_attr\\(bootstrap, feature\\(let_else\\)#"
 2022-09-15 21:06:45 +02:00
b-naber
6af8fb7936 address review again 2022-09-14 17:30:25 +02:00
Eric Holk
cf04547b0b Address code review comments 2022-09-13 14:50:12 -07:00