Commit Graph

645 Commits

Author SHA1 Message Date
AndyJado
057d8e5c43 struct error E0505 2022-11-09 21:15:31 +08:00
AndyJado
abf259cc54 var_subdiag refinement
trim old
2022-11-09 21:15:29 +08:00
AndyJado
a0cee0ab90 remove old var_span_path_only
doc comment
2022-11-09 20:51:43 +08:00
AndyJado
e636af7dfd lint auto pass
Revert "lint auto pass"

This reverts commit e58e4466384924c491a932d3f18ef50ffa5a5065.
2022-11-09 20:42:16 +08:00
Jakob Degen
ba359d8a51 Add support for custom MIR parsing 2022-11-08 23:13:15 -08:00
bors
91385d5776 Auto merge of #104179 - Manishearth:rollup-yvsx5hh, r=Manishearth
Rollup of 7 pull requests

Successful merges:

 - #100508 (avoid making substs of type aliases late bound when used as fn args)
 - #101381 (Test that target feature mix up with homogeneous floats is sound)
 - #103353 (Fix Access Violation when using lld & ThinLTO on windows-msvc)
 - #103521 (Avoid possible infinite  loop when next_point reaching the end of file)
 - #103559 (first move on a nested span_label)
 - #103778 (Update several crates for improved support of the new targets)
 - #103827 (Properly remap and check for substs compatibility in `confirm_impl_trait_in_trait_candidate`)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
2022-11-09 04:43:43 +00:00
Manish Goregaokar
7dfe1e1664
Rollup merge of #103559 - AndyJado:var_span_label, r=davidtwco
first move on a nested span_label

trying not to be smart this time.
2022-11-08 21:03:53 -05:00
bors
bc2504a83c Auto merge of #103171 - jackh726:gen-interior-hrtb-error, r=cjgillot
Better error for HRTB error from generator interior

cc #100013

This is just a first pass at an error. It could be better, and shouldn't really be emitted in the first place. But this is better than what was being emitted before.
2022-11-09 02:02:28 +00:00
yukang
1f21b96dce add 'ty_error_with_guaranteed' and 'const_error_with_guaranteed' 2022-11-08 11:17:46 +08:00
Dylan DPC
77a44ab568
Rollup merge of #103865 - compiler-errors:fallback-has-occurred-tracking, r=eholk
Move `fallback_has_occurred` state tracking to `FnCtxt`

Removes a ton of callsites that defaulted to `false`
2022-11-08 11:23:51 +05:30
Jack Huey
00e314d5ed Add an optional Span to BrAnon and use it to print better error for HRTB error from generator interior 2022-11-07 17:39:29 -05:00
bors
ca08a32655 Auto merge of #103218 - CastilloDel:infer, r=jackh726
Remove #![allow(rustc::potential_query_instability)] from rustc_infer

Related to #84447

This PR probably needs to be benchmarked to check for regressions.
2022-11-07 07:38:05 +00:00
bors
e30fb6a26f Auto merge of #102618 - aliemjay:simplify-closure-promote, r=compiler-errors
rework applying closure requirements in borrowck

Previously the promoted closure constraints were registered under the category `ConstraintCategory::ClosureBounds` in `type_check::prove_closure_bounds()` and then mapped back their original category in `regions_infer::best_blame_constraint` using the complicated map `closure_bounds_mapping`.

Now we're registering promoted constraints under their original category and span earlier in `type_check::prove_closure_bounds`.

See commit messages.

Fixes #99245
2022-11-06 05:26:09 +00:00
Michael Goulet
bc345d7bd0 Move fallback_has_occurred to FnCtxt 2022-11-06 02:40:25 +00:00
AndyJado
e49d10db14 first move on a nested span_label
Apply suggestions from code review

Co-authored-by: David Wood <agile.lion3441@fuligin.ink>
2022-11-05 19:43:48 +08:00
Ali MJ Al-Nasrawy
02f78fdb94 use spans in TypeTest rather than mir::Location
Spans are independent of the body being borrow-checked, so they don't
need remapping when promoting type-tests and they yield more specific
error spans inside bodies of closures/inline consts.
2022-11-05 07:36:47 +03:00
Ali MJ Al-Nasrawy
df668b9fb9 simplify applying closure requirements
Don't use `ConstraintCategory::ClosureBounds`!
Set the category and the span for the promoted constraints to that of
the original constraint earlier than before.
This eliminates the need for `closure_bounds_mapping`.
2022-11-05 07:36:42 +03:00
Matthias Krüger
ad01a37ca9
Rollup merge of #103868 - compiler-errors:trait-engine-less, r=jackh726
Use `TraitEngine` (by itself) less

Replace `TraitEngine` in favor of `ObligationCtxt` or `fully_solve_*`, improving code readability.
2022-11-05 00:02:04 +01:00
Matthias Krüger
d10187f040
Rollup merge of #103780 - compiler-errors:bound-closure-lifetimes, r=jackh726
Fix late-bound lifetime closure ICEs in HIR typeck and MIR borrowck

During HIR typeck, we need to teach astconv to treat late-bound regions within a closure body as free, fixing escaping bound vars ICEs in both of the issues below.

However, this then gets us to MIR borrowck, which itself needs to be taught how to instantiate free region vids for late-bound regions that come from items that _aren't_ the typeck root (for now, just closures).

Fixes #103771
Fixes #103736
2022-11-04 12:18:01 +01:00
Michael Goulet
41e4218d2a Use TraitEngine less 2022-11-02 04:11:05 +00:00
Manish Goregaokar
69e705564d
Rollup merge of #103575 - Xiretza:suggestions-style-attr, r=davidtwco
Change #[suggestion_*] attributes to use style="..."

As discussed [on Zulip](https://rust-lang.zulipchat.com/#narrow/stream/336883-i18n/topic/.23100717.20tool_only_span_suggestion), this changes `#[(multipart_)suggestion_{short,verbose,hidden}(...)]` attributes to plain `#[(multipart_)suggestion(...)]` attributes with a `style = "{short,verbose,hidden}"` parameter.

It also adds a new style, `tool-only`, that corresponds to `tool_only_span_suggestion`/`tool_only_multipart_suggestion` and causes the suggestion to not be shown in human-readable output at all.

Best reviewed commit-by-commit, there's a bit of noise in there.

cc #100717 `@compiler-errors`
r? `@davidtwco`
2022-11-01 20:00:38 -04:00
bors
e70cbef0c5 Auto merge of #103590 - compiler-errors:ocx-more, r=lcnr
(almost) Always use `ObligationCtxt` when dealing with canonical queries

Hope this is a step in the right direction. cc rust-lang/types-team#50.

r? `@lcnr`
2022-11-01 12:15:10 +00:00
Michael Goulet
2768c2fb25 Add bug! back to late_bound_vars query 2022-10-31 21:25:08 +00:00
Michael Goulet
4427af0827 Make external/local late-bound region registration more explicit 2022-10-31 21:25:08 +00:00
Michael Goulet
f27bdf1750 Collect late-bound regions from all closure parents in closure_mapping 2022-10-31 21:25:08 +00:00
Michael Goulet
5ba1556e0d Create NLL infer vars for late-bound regions from closures 2022-10-31 21:25:08 +00:00
Guillaume Gomez
2414a4c31a
Rollup merge of #103625 - WaffleLapkin:no_tyctxt_dogs_allowed, r=compiler-errors
Accept `TyCtxt` instead of `TyCtxtAt` in `Ty::is_*` functions

Functions in answer:

- `Ty::is_freeze`
- `Ty::is_sized`
- `Ty::is_unpin`
- `Ty::is_copy_modulo_regions`

This allows to remove a lot of useless `.at(DUMMY_SP)`, making the code a bit nicer :3

r? `@compiler-errors`
2022-10-29 14:18:03 +02:00
CastilloDel
e9502010b4 Remove #![allow(rustc::potential_query_instability)] from rustc_infer
Change reported_violations to use IndexSet

It is being used to iterate and to insert, without a lot of lookups
so hopefully it won't be a perf hit

Change MiniGraph.nodes to use IndexSet

It is being used to iterate and to insert, without performing lookups
so hopefully it won't be a perf hit

Change RegionConstraintData.givens to a FxIndexSet

This might result in a perf hit. Remove was being used in `givens`,
and `FxIndexSet` doesn't allow calling remove without losing the
fixed iteration order. So it was necessary to change remove to
`shift_remove`, but this method is slower.

Change OpaqueTypesVisitor to use stable sets and maps

This could also be a perf hit.

Make TraitObject visitor use a stable set
2022-10-28 15:32:49 +02:00
Matthias Krüger
84663cee39
Rollup merge of #103641 - compiler-errors:issue-103624, r=cjgillot
Don't carry MIR location in `ConstraintCategory::CallArgument`

It turns out that `ConstraintCategory::CallArgument` cannot just carry a MIR location in it, since we may bubble them up to totally different MIR bodies.

So instead, revert the commit a6b5f95fb0, and instead just erase regions from the original `Option<Ty<'tcx>>` that it carried, so that it doesn't ICE with the changes in #103220.

Best reviewed in parts -- the first is just a revert, and the second is where the meaningful changes happen.

Fixes #103624
2022-10-28 07:06:43 +02:00
Michael Goulet
4e0c27bbfd Erase regions from CallArgument, add test + bless 2022-10-27 16:26:55 +00:00
Michael Goulet
dce44faf5b Revert "Make ClosureOutlivesRequirement not rely on an unresolved type"
This reverts commit a6b5f95fb0.
2022-10-27 16:15:11 +00:00
Michael Goulet
d793d80cf7 (almost) Always use ObligationCtxt when dealing with canonical queries 2022-10-27 15:43:33 +00:00
Matthias Krüger
16e74c78a1
Rollup merge of #103255 - oli-obk:opaque_wrong_eq_relation, r=compiler-errors
Clean up hidden type registration

work on https://github.com/rust-lang/rust/issues/101186

Actually passing down the relation and using it instead of `eq` for the hidden type comparison has *no* effect whatsoever and allows for no further improvements at the call sites. I decided the increased complexity was not worth it and thus did not include that change in this PR.

r? `@compiler-errors`
2022-10-27 15:03:55 +02:00
Maybe Waffle
a17ccfa621 Accept TyCtxt instead of TyCtxtAt in Ty::is_* functions
Functions in answer:

- `Ty::is_freeze`
- `Ty::is_sized`
- `Ty::is_unpin`
- `Ty::is_copy_modulo_regions`
2022-10-27 15:06:08 +04:00
Xiretza
cd621be782 Convert all #[suggestion_*] attributes to #[suggestion(style = "...")]
Using the following command:

find compiler/ -type f -name '*.rs' -exec perl -i -gpe \
    's/(#\[\w*suggestion)_(short|verbose|hidden)\(\s*(\S+,)?/\1(\3style = "\2",/g' \
    '{}' +
2022-10-26 15:04:09 +02:00
Oli Scherer
196a429a67 Use the general type API instead of directly accessing register_hidden_type 2022-10-25 13:27:06 +00:00
Oli Scherer
14caf7396d Pull opaque type handling out of the type relating delegate 2022-10-25 13:27:04 +00:00
Yuki Okushi
6383540130
Rollup merge of #103382 - compiler-errors:anon-apit-lt-region-ice, r=cjgillot
Don't ICE when reporting borrowck errors involving regions from `anonymous_lifetime_in_impl_trait`

The issue here is that when we have:

```
trait Trait<'a> { .. }

fn foo(arg: impl Trait) { .. }
```

The anonymous lifetime `'_` that we generate for `arg: impl Trait` doesn't end up in the argument type (which is a param) but in a where-clause of the function, in a predicate whose self type is that param ty.

Fixes #101660

r? ``@cjgillot``
2022-10-25 08:01:28 +09:00
Nilstrieb
c65ebae221
Migrate all diagnostics 2022-10-23 10:09:44 +02:00
Michael Goulet
e025306fa0 Don't ICE on regions from anonymous_lifetime_in_impl_trait 2022-10-22 03:00:58 +00:00
b4den
c87567cbfa Add context to compiler error message
Changed `creates a temporary which is freed while still in use` to
`creates a temporary value which is freed while still in use`
2022-10-20 15:44:25 +01:00
bors
542febd2d3 Auto merge of #103290 - matthiaskrgr:rollup-ngozai3, r=matthiaskrgr
Rollup of 6 pull requests

Successful merges:

 - #103197 (Stabilize proc_macro::Span::source_text)
 - #103251 (Fix item declaration highlighting)
 - #103262 (Adjusting test to needs-unwind, with linking issue)
 - #103268 (rustdoc: remove no-op CSS `nav.sub { font-size: 1rem }`)
 - #103272 (Remove extra spaces in docs)
 - #103276 (Erase regions before checking for `Default` in uninitialized binding error)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
2022-10-20 13:33:50 +00:00
Matthias Krüger
e29ecb70af
Rollup merge of #103276 - compiler-errors:default-on-uninit-ice, r=TaKO8Ki
Erase regions before checking for `Default` in uninitialized binding error

Fixes #103250
2022-10-20 07:58:58 +02:00
bors
4b3b731b55 Auto merge of #103220 - compiler-errors:deny-infers, r=lcnr
Deny hashing ty/re/ct inference variables

cc `@cjgillot` and https://github.com/rust-lang/rust/pull/102695#issuecomment-1275706528
r? `@lcnr`

best reviewed one commit at a time, mostly because the second commit that fixes `ClosureOutlivesRequirement` is mostly noise because of losing its `<'tcx>` lifetime parameter.
2022-10-20 05:56:56 +00:00
bors
cb9467515b Auto merge of #102417 - oli-obk:opaque_lifetimes2, r=jackh726
Require lifetime bounds for opaque types in order to allow hidden types to capture said lifetimes

fixes #96996

cc `@aliemjay`
2022-10-20 00:22:17 +00:00
Michael Goulet
c5c9f74829 Erase regions before checking for default in uninitialized binding error 2022-10-19 23:36:28 +00:00
Michael Goulet
a6b5f95fb0 Make ClosureOutlivesRequirement not rely on an unresolved type 2022-10-19 17:10:59 +00:00
lcnr
e8150fa60c mir constants: type traversing bye bye 2022-10-17 10:54:01 +02:00
bors
11432fe952 Auto merge of #102080 - yanchen4791:issue-99824-fix, r=cjgillot
Fix missing explanation of where the borrowed reference is used when the same borrow occurs multiple times due to loop iterations

Fix #99824.

Problem of the issue:
If a borrow occurs in a loop, the borrowed reference could be invalidated at the same place at next iteration of the loop. When this happens, the point where the borrow occurs is the same as the intervening point that might invalidate the reference in the loop. This causes a problem for the current code finding the point where the resulting reference is used, so that the explanation of the cause will be missing. As the second point of "explain all errors in terms of three points" (see [leveraging intuition framing errors in terms of points"](https://rust-lang.github.io/rfcs/2094-nll.html#leveraging-intuition-framing-errors-in-terms-of-points), this explanation is very helpful for user to understand the error.

In the current implementation, the searching region for finding the location where the borrowed reference is used is limited to between the place where the borrow occurs and the place where the reference is invalidated. If those two places happen to be the same, which indicates that the borrow and invalidation occur at the same place in a loop, the search will fail.

One solution to the problem is when these two places are the same,  find the terminator of the loop, and then use the location of the loop terminator instead of the location of the borrow for the region to find the place where the borrowed reference is used.
2022-10-16 07:40:56 +00:00
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
Oli Scherer
1dc2119c03 Require lifetime bounds for opaque types in order to allow hidden types to capture said lifetimes 2022-10-14 08:15:51 +00:00
Rageking8
7122abaddf more dupe word typos 2022-10-14 12:57:56 +08:00
bors
60bd3f9677 Auto merge of #102700 - oli-obk:0xDEAD_TAIT, r=compiler-errors
Check hidden types in dead code

fixes #99490

r? `@compiler-errors`

best reviewed commit by commit
2022-10-13 22:39:05 +00:00
Dylan DPC
5e04567ac7
Rollup merge of #102187 - b-naber:inline-const-source-info, r=eholk
Use correct location for type tests in promoted constants

Previously we forgot to remap the location in a type test collected when visiting the body of a promoted constant back to the usage location, causing an ICE when trying to get span information for that type test.

Fixes https://github.com/rust-lang/rust/issues/102117
2022-10-12 11:11:24 +05:30
Michael Howell
bf37054b1f
Rollup merge of #99818 - aliemjay:fix-closure-normalize, r=jackh726
don't ICE when normalizing closure input tys

We were ICEing while rendering diagnostics because `universe_causes` is expected to track every universe created in the typeck's infcx.

`normalize_and_add_constraints` doesn't update `universe_causes`
when creating new universes, causing an ICE. Remove it!

Add spans to better track normalization constraints.

Fix couple places where `universe_causes` is not updated correctly to
track newly added universes.

Fixes #102800

~Fixess #99665~ (UPDATE: no longer true; the issue has a different failure path than when this PR was created and should be fixed by #101708, but the changes in this PR are still correct and should prevent potential future ICEs)
2022-10-08 18:14:59 -07:00
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
Ali MJ Al-Nasrawy
fc3d7eb91d don't ICE when normalizing closure input tys
`normalize_and_add_constraints` doesn't add entries in `universe_causes`
when creating new universes, causing an ICE. Remove it!

Add spans to track normalization constraints.

Fix couple places where `universe_causes` is not updated correctly to
track newly added universes.
2022-10-08 04:56:25 +03:00
Oli Scherer
70d39abbc2 Remap hidden types from typeck before storing them in the TypeckResult 2022-10-07 19:43:46 +00:00
Oli Scherer
9eb69e82e0 Move ReverseMapper logic onto OpaqueHiddenType 2022-10-07 19:43:46 +00:00
Oli Scherer
d643ae1bbf Remove some dead code 2022-10-07 19:36:32 +00:00
Cameron Steffen
283abbf0e7 Change InferCtxtBuilder from enter to build 2022-10-07 07:10:40 -05:00
Cameron Steffen
349415d1c6 Remove TypeckResults from InferCtxt 2022-10-07 07:06:19 -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
Oli Scherer
c7b6ebdf7c It's not about types or consts, but the lack of regions 2022-10-04 14:10:44 +00:00
reez12g
ebcec30182 Remove 'E0312' from 'compile_fail,E0312' statement temporarily 2022-10-02 11:00:43 +09:00
Michael Goulet
c1c3dacc78 Generate synthetic impl region even in closure body in associated fn 2022-09-29 22:32:28 +00:00
reez12g
cf31a29492 Mark ignore on error code docs in compiler/rustc_borrowck/src/region_infer/mod.rs 2022-09-29 16:49:16 +09:00
reez12g
c2ad8d2551 Mark ignore on error code docs in compiler/rustc_borrowck/src/diagnostics/region_errors.rs 2022-09-29 16:49:15 +09:00
Yan Chen
b3bf931aa2 Fix missing explanation of where borrowed reference is used when the borrow occurs in loop iteration 2022-09-28 15:27:56 -07:00
bors
e1d7dec558 Auto merge of #102051 - pietroalbini:pa-bootstrap-update, r=Mark-Simulacrum
Update bootstrap compiler to 1.65.0

This PR updates the bootstrap compiler to Rust 1.65.0, removing the various `cfg(bootstrap)`s.

r? `@Mark-Simulacrum`
2022-09-26 14:22:43 +00:00
bors
84946fe241 Auto merge of #102184 - chenyukang:fix-102087-add-binding-sugg, r=nagisa
Suggest Default::default() when binding isn't initialized

Fixes #102087
2022-09-26 11:41:58 +00:00
Pietro Albini
3975d55d98
remove cfg(bootstrap) 2022-09-26 10:14:45 +02:00
yukang
672e3f4d77 fix #102087, Suggest Default::default() when binding isn't initialized 2022-09-26 07:56:26 +08:00
bors
f5193a9fcc Auto merge of #95474 - oli-obk:tait_ub, r=jackh726
Neither require nor imply lifetime bounds on opaque type for well formedness

The actual hidden type can live arbitrarily longer than any individual lifetime and arbitrarily shorter than all but one of the lifetimes.

fixes #86218
fixes #84305

This is a **breaking change** but it is a necessary soundness fix
2022-09-25 19:15:26 +00:00
fee1-dead
084029f39d
Rollup merge of #101431 - compiler-errors:move-place-ty-for-move-place-sugg, r=cjgillot
Look at move place's type when suggesting mutable reborrow

Not sure why we are looking at the use site's ty instead of the move site's ty in order to suggest reborrowing the move site, but it was suppressing a perfectly valid reborrow suggestion.

r? `@estebank` who i think touched this last in 520461f1fb, though that was quite a while ago so feel free to reassign.
2022-09-25 22:06:37 +08:00
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
b-naber
72b3347d00 use correct location for type tests in promoted consts 2022-09-23 14:03:49 +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
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
37928f5986 Neither require nor imply lifetime bounds on opaque type for well formedness 2022-09-21 13:11:54 +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
lcnr
647052fc04 remove the Subst trait, always use EarlyBinder 2022-09-19 11:37:27 +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
Jack Huey
e7ca6e1b47 Use Predicate ConstraintCategory when normalizing 2022-09-17 11:46:05 -04:00
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
e09242d5b8 Final bits 2022-09-16 17:47:53 -04:00
Jack Huey
f1767dbb42 Add ExtraConstraintInfo 2022-09-16 17:33:12 -04:00
Jack Huey
ec17be2656 Add outlives_constraint to BlameConstraint 2022-09-16 17:08:35 -04:00
Jack Huey
6075877c89 Pass ConstraintCategory thorough a few more places 2022-09-16 16:44:18 -04:00
Jack Huey
a46376e247 Make QueryOutlivesConstraint contain a ConstraintCategory 2022-09-16 16:15:41 -04:00
Jack Huey
92b759f517 Revert "Better errors for implied static bound"
This reverts commit c75817b0a7.
2022-09-16 09:47:07 -04:00
Jack Huey
bba514b7b4 Revert "Use Predicate ConstraintCategory when normalizing"
This reverts commit aae37f8763.
2022-09-16 09:01:28 -04:00
Oli Scherer
40e2de8c41 Revert "Revert "Rollup merge of #98582 - oli-obk:unconstrained_opaque_type, r=estebank""
This reverts commit 4a742a691e.
2022-09-16 11:36:39 +00:00
Deadbeef
5ead742e18 remap ParamEnv with obligation 2022-09-16 12:08:46 +08:00
Deadbeef
08aeb1aa9b unconditionally remap to nonconst in borrowck 2022-09-16 12:08:46 +08:00