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321 Commits

Author SHA1 Message Date
Jack Huey
167b70692b Remove expect_anon and expect_anon_placeholder in favor of var 2023-04-06 23:01:38 -04:00
Jack Huey
4646b3df6a Use BoundTy and BoundRegion instead of kind of PlaceholderTy and PlaceholderRegion 2023-04-06 23:01:35 -04:00
Matthias Krüger
ac229c2819 fix clippy::iter_kv_map 2023-04-01 23:44:16 +02:00
Michael Goulet
3a36a093dd Rename AliasEq -> AliasRelate 2023-03-23 05:56:40 +00:00
Nicholas Nethercote
c09f5b6a6b Add mk_canonical_var_infos_from_iter. 
It's missing, and is useful in two places.
 2023-02-24 07:33:02 +11:00
Nicholas Nethercote
11c2c596e4 Rename mk_{ty,region} as mk_{ty,region}_from_kind. 
To discourage accidental use -- there are more specific `mk_*` functions
for all `Ty` and `Region` kinds.
 2023-02-24 07:33:00 +11:00
Nicholas Nethercote
2200911616 Rename many interner functions. 
(This is a large commit. The changes to
`compiler/rustc_middle/src/ty/context.rs` are the most important ones.)

The current naming scheme is a mess, with a mix of `_intern_`, `intern_`
and `mk_` prefixes, with little consistency. In particular, in many
cases it's easy to use an iterator interner when a (preferable) slice
interner is available.

The guiding principles of the new naming system:
- No `_intern_` prefixes.
- The `intern_` prefix is for internal operations.
- The `mk_` prefix is for external operations.
- For cases where there is a slice interner and an iterator interner,
  the former is `mk_foo` and the latter is `mk_foo_from_iter`.

Also, `slice_interners!` and `direct_interners!` can now be `pub` or
non-`pub`, which helps enforce the internal/external operations
division.

It's not perfect, but I think it's a clear improvement.

The following lists show everything that was renamed.

slice_interners
- const_list
  - mk_const_list -> mk_const_list_from_iter
  - intern_const_list -> mk_const_list
- substs
  - mk_substs -> mk_substs_from_iter
  - intern_substs -> mk_substs
  - check_substs -> check_and_mk_substs (this is a weird one)
- canonical_var_infos
  - intern_canonical_var_infos -> mk_canonical_var_infos
- poly_existential_predicates
  - mk_poly_existential_predicates -> mk_poly_existential_predicates_from_iter
  - intern_poly_existential_predicates -> mk_poly_existential_predicates
  - _intern_poly_existential_predicates -> intern_poly_existential_predicates
- predicates
  - mk_predicates -> mk_predicates_from_iter
  - intern_predicates -> mk_predicates
  - _intern_predicates -> intern_predicates
- projs
  - intern_projs -> mk_projs
- place_elems
  - mk_place_elems -> mk_place_elems_from_iter
  - intern_place_elems -> mk_place_elems
- bound_variable_kinds
  - mk_bound_variable_kinds -> mk_bound_variable_kinds_from_iter
  - intern_bound_variable_kinds -> mk_bound_variable_kinds

direct_interners
- region
  - intern_region (unchanged)
- const
  - mk_const_internal -> intern_const
- const_allocation
  - intern_const_alloc -> mk_const_alloc
- layout
  - intern_layout -> mk_layout
- adt_def
  - intern_adt_def -> mk_adt_def_from_data (unusual case, hard to avoid)
  - alloc_adt_def(!) -> mk_adt_def
- external_constraints
  - intern_external_constraints -> mk_external_constraints

Other
- type_list
  - mk_type_list -> mk_type_list_from_iter
  - intern_type_list -> mk_type_list
- tup
  - mk_tup -> mk_tup_from_iter
  - intern_tup -> mk_tup
 2023-02-24 07:32:24 +11:00
Michael Goulet
298ae8c721 Rename ty_error_with_guaranteed to ty_error, ty_error to ty_error_misc 2023-02-22 22:23:45 +00:00
Alan Egerton
695072daa6
Remove type-traversal trait aliases 2023-02-22 17:04:58 +00:00
Boxy
e919d7e348 Add Clause::ConstArgHasType variant 2023-02-17 09:30:33 +00:00
Kyle Matsuda
c183110cc2 remove bound_type_of query; make type_of return EarlyBinder; change type_of in metadata 2023-02-16 17:05:56 -07:00
Kyle Matsuda
d822b97a27 change usages of type_of to bound_type_of 2023-02-16 17:01:52 -07:00
Nicholas Nethercote
cef9004f5a Add specialized variants of mk_region. 
Much like there are specialized variants of `mk_ty`. This will enable
some optimization in the next commit.

Also rename the existing `re_error*` functions as `mk_re_error*`, for
consistency.
 2023-02-15 09:02:44 +11:00
Alan Egerton
63ad5d0522
Rename folder traits' tcx method to interner 2023-02-13 10:24:51 +00:00
Alan Egerton
9783fcc13b
Make folding traits generic over the Interner 2023-02-13 10:24:49 +00:00
Alan Egerton
dea342d861
Make visiting traits generic over the Interner 2023-02-13 10:24:49 +00:00
Alan Egerton
ba55a453eb
Alias folding/visiting traits instead of re-export 2023-02-13 10:24:46 +00:00
Nicholas Nethercote
7a72560154 Reduce direct mk_ty usage. 
We use more specific `mk_*` functions in most places, might as well use
them as much as possible.
 2023-02-13 09:32:48 +11:00
bors
1623ab0246 Auto merge of #107507 - BoxyUwU:deferred_projection_equality, r=lcnr 
Implement `deferred_projection_equality` for erica solver

Somewhat of a revival of #96912. When relating projections now emit an `AliasEq` obligation instead of attempting to determine equality of projections that may not be as normalized as possible (i.e. because of lazy norm, or just containing inference variables that prevent us from resolving an impl). Only do this when the new solver is enabled
 2023-02-11 05:46:24 +00:00
Boxy
23ab2464be add AliasEq to PredicateKind 2023-02-10 13:44:46 +00:00
bors
d1ac43a9b9 Auto merge of #107652 - estebank:re_error, r=oli-obk 
Introduce `ReError`

CC #69314

r? `@nagisa`
 2023-02-10 10:10:12 +00:00
Jack Huey
0637b6b471 Update implied_outlives_bounds to properly register implied bounds behind normalization 2023-02-09 21:08:11 -05:00
Jack Huey
1a663c0f53 Cleanup free_region_relations a bit 2023-02-09 20:38:27 -05:00
Esteban Küber
861f451235 Change to ReError(ErrorGuaranteed) 2023-02-09 10:26:49 +00:00
Esteban Küber
30cf7a3f51 Introduce ReError 
CC #69314
 2023-02-09 10:26:49 +00:00
klensy
4f5f9f0a13 remove unused imports 2023-02-06 17:40:18 +03:00
Michael Goulet
0e98a162c8 Track bound types like bound regions 2023-01-30 22:18:20 +00:00
bors
d117135f5a Auto merge of #106253 - nbdd0121:upcast, r=compiler-errors 
Skip possible where_clause_object_safety lints when checking `multiple_supertrait_upcastable`

Fix #106247

To achieve this, I lifted the `WhereClauseReferencesSelf` out from `object_safety_violations` and move it into `is_object_safe` (which is changed to a new query).

cc `@dtolnay`
r? `@compiler-errors`
 2023-01-29 10:20:25 +00:00
bors
1e225413a2 Auto merge of #107303 - compiler-errors:intern-canonical-var-values, r=lcnr 
Intern `CanonicalVarValues`

So that they are copy ✨
 2023-01-28 19:41:21 +00:00
Gary Guo
94e59cb6e2 Rename is_object_safe to check_is_object_safe to hint side effects 2023-01-28 15:07:57 +00:00
Camille GILLOT
1974b6b68d Introduce GeneratorWitnessMIR. 2023-01-27 18:58:44 +00:00
Camille GILLOT
cb873b2d93 Separate trait selection from ambiguity reporting. 2023-01-27 18:57:10 +00:00
Kyle Matsuda
c2414dfaa4 change fn_sig query to use EarlyBinder; remove bound_fn_sig query; add EarlyBinder to fn_sig in metadata 2023-01-26 20:28:25 -07:00
Michael Goulet
4ff674f942 Intern CanonicalVarValues 2023-01-26 20:33:40 +00:00
Vincenzo Palazzo
7d2c1103d7 fix: use LocalDefId instead of HirId in trait res 
use LocalDefId instead of HirId in trait resolution to simplify
the obligation clause resolution

Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
 2023-01-23 11:42:18 +00:00
Ali MJ Al-Nasrawy
a7a842027c even more unify Projection/Opaque in outlives code 2023-01-19 15:31:53 +03:00
Matthias Krüger
68f12338af
Rollup merge of #104505 - WaffleLapkin:no-double-spaces-in-comments, r=jackh726 
Remove double spaces after dots in comments

Most of the comments do not have double spaces, so I assume these are typos.
 2023-01-17 20:21:25 +01:00
Maybe Waffle
6a28fb42a8 Remove double spaces after dots in comments 2023-01-17 08:09:33 +00:00
Matthias Krüger
6b49435480
Rollup merge of #106829 - compiler-errors:more-alias-combine, r=spastorino 
Unify `Opaque`/`Projection` handling in region outlives code

They share basically identical paths in most places which are even easier to unify now that they're both `ty::Alias`

r? types
 2023-01-17 05:25:22 +01:00
Michael Goulet
90df86f474 Remove bound_{explicit,}_item_bounds 2023-01-15 15:36:06 +00:00
Michael Goulet
9b28edb6d7 Make InstantiatedPredicates impl IntoIterator 2023-01-15 15:36:06 +00:00
Kyle Matsuda
f29a334c90 change impl_trait_ref query to return EarlyBinder; remove bound_impl_trait_ref query; add EarlyBinder to impl_trait_ref in metadata 2023-01-14 00:29:56 -07:00
Kyle Matsuda
be130b57d4 change usages of impl_trait_ref to bound_impl_trait_ref 2023-01-14 00:23:32 -07:00
Michael Goulet
1ea6862db3 Unify Opaque/Projection handling in region outlives code 2023-01-13 23:53:28 +00:00
Yuki Okushi
e5e116dca9
Rollup merge of #106204 - compiler-errors:no-take-opaques-in-compare, r=oli-obk 
No need to take opaques in `check_type_bounds`

`InferCtxt` already has its defining use anchor set to err

r? ``@oli-obk``
 2023-01-10 08:05:34 +09:00
Michael Goulet
f769d34291 Assert defining anchor is set in take_opaque_types 2023-01-09 18:14:28 +00:00
Ali MJ Al-Nasrawy
c6a17bf8bc make ascribe_user_type a TypeOp 
Projection types in user annotations may contain inference variables.
This makes the normalization depend on the unification with the actual
type and thus requires a separate TypeOp to track the obligations.
Otherwise simply calling `TypeChecker::normalize` would ICE with
"unexpected ambiguity"
 2023-01-07 13:41:41 +03:00
Ali MJ Al-Nasrawy
d227506683 don't normalize in astconv 
We delay projection normalization to further stages in order to
register user type annotations before normalization in HIR typeck.

There are two consumers of astconv: ItemCtxt and FnCtxt.
The former already expects unnormalized types from astconv, see its
AstConv trait impl.
The latter needs `RawTy` for a cleaner interface.

Unfortunately astconv still needs the normalization machinery in
order to resolve enum variants that have projections in the self type,
e.g. `<<T as Trait>::Assoc>::StructVariant {}`.
This is why `AstConv::normalize_ty_2` is necessary.
 2023-01-07 13:38:38 +03:00
nils
fd7a159710 Fix uninlined_format_args for some compiler crates 
Convert all the crates that have had their diagnostic migration
completed (except save_analysis because that will be deleted soon and
apfloat because of the licensing problem).
 2023-01-05 19:01:12 +01:00
Jeremy Stucki
3dde32ca97
rustc: Remove needless lifetimes 2022-12-20 22:10:40 +01:00
Oli Scherer
a5cd3bde95 Ensure no one constructs AliasTys themselves 2022-12-14 15:36:39 +00:00
Michael Goulet
7196973c3e Remove chalk lowering for AliasTy 2022-12-13 17:48:55 +00:00
Michael Goulet
96cb18e864 Combine identical alias arms 2022-12-13 17:48:55 +00:00
Michael Goulet
61adaf8187 Combine projection and opaque into alias 2022-12-13 17:48:55 +00:00
Michael Goulet
c13bd83528 squash OpaqueTy and ProjectionTy into AliasTy 2022-12-13 17:40:27 +00:00
Michael Goulet
5c6afb850c ProjectionTy.item_def_id -> ProjectionTy.def_id 2022-12-13 17:34:44 +00:00
Michael Goulet
7f3af72606 Use ty::OpaqueTy everywhere 2022-12-13 17:29:26 +00:00
Michael Goulet
3b9daac6a2 Move some suggestions from error_reporting to error_reporting::suggest 2022-12-08 05:58:30 +00:00
Michael Goulet
25a6daccab Move codegen_select_candidate to a rustc_traits 2022-12-08 05:16:57 +00:00
Michael Goulet
1e236acd05 Make ObligationCtxt::normalize take cause by borrow 2022-11-28 17:35:40 +00:00
Michael Goulet
fc710832ea partially_normalize_... -> At::normalize 2022-11-28 17:35:39 +00:00
Michael Goulet
f12e772b83 Rename At::normalize to At::query_normalize 2022-11-28 17:32:35 +00:00
Matthias Krüger
1fe18a5dad
Rollup merge of #104906 - spastorino:remove-ascribeusertypecx, r=compiler-errors 
Remove AscribeUserTypeCx

r? ``@compiler-errors``

This basically inlines `AscribeUserTypeCx::relate_mir_and_user_ty` into `type_op_ascribe_user_type_with_span` which is the only place where it's used and makes direct use of `ObligationCtxt` API.
 2022-11-26 10:39:12 +01:00
Santiago Pastorino
3c9b30e658
Define all clauses as dummy_with_span as the usages are all equivalent 2022-11-25 16:00:08 -03:00
Santiago Pastorino
aaa1db63ce
Remove AscribeUserTypeCx 2022-11-25 15:25:00 -03:00
Santiago Pastorino
974e2837bb
Introduce PredicateKind::Clause 2022-11-25 00:04:54 -03:00
bors
b3bc6bf312 Auto merge of #103693 - HKalbasi:master, r=oli-obk 
Make rustc_target usable outside of rustc

I'm working on showing type size in rust-analyzer (https://github.com/rust-lang/rust-analyzer/pull/13490) and I currently copied rustc code inside rust-analyzer, which works, but is bad. With this change, I would become able to use `rustc_target` and `rustc_index` directly in r-a, reducing the amount of copy needed.

This PR contains some feature flag to put nightly features behind them to make crates buildable on the stable compiler + makes layout related types generic over index type + removes interning of nested layouts.
 2022-11-24 20:29:13 +00:00
hkalbasi
27fb904d68 move some layout logic to rustc_target::abi::layout 2022-11-24 16:26:12 +03:30
Arpad Borsos
9f36f988ad
Avoid GenFuture shim when compiling async constructs 
Previously, async constructs would be lowered to "normal" generators,
with an additional `from_generator` / `GenFuture` shim in between to
convert from `Generator` to `Future`.

The compiler will now special-case these generators internally so that
async constructs will *directly* implement `Future` without the need
to go through the `from_generator` / `GenFuture` shim.

The primary motivation for this change was hiding this implementation
detail in stack traces and debuginfo, but it can in theory also help
the optimizer as there is less abstractions to see through.
 2022-11-24 10:04:27 +01:00
Santiago Pastorino
859b147d4f
Pass ObligationCtxt from enter_canonical_trait_query and use ObligationCtxt API 2022-11-23 09:36:03 -03:00
Manish Goregaokar
53eab246db
Rollup merge of #103488 - oli-obk:impl_trait_for_tait, r=lcnr 
Allow opaque types in trait impl headers and rely on coherence to reject unsound cases

r? ````@lcnr````

fixes #99840
 2022-11-22 22:54:38 -05:00
Oli Scherer
ec8d01fdcc Allow iterators instead of requiring slices that will get turned into iterators 2022-11-21 20:33:55 +00:00
Oli Scherer
ae80c764d4 Add an always-ambiguous predicate to make sure that we don't accidentlally allow trait resolution to prove false things during coherence 2022-11-21 16:35:04 +00:00
Matthias Krüger
844e3fb928
Rollup merge of #104595 - compiler-errors:poly-existential-predicate, r=lcnr 
Add `PolyExistentialPredicate` type alias

Wrapping `ExistentialPredicate`s in a binder is very common, and this alias already exists for the `PolyExistential{TraitRef,Projection}` types.
 2022-11-21 14:11:11 +01:00
bors
7477c1f4f7 Auto merge of #104522 - RalfJung:try_normalize_after_erasing_regions, r=oli-obk 
try_normalize_after_erasing_regions: promote an assertion to always run

In https://github.com/rust-lang/miri/issues/2433 this assertion has been seen to trigger, so it might be worth actually checking this? Regressing debug assertions are very easy to miss until much later, and then they become quite hard to debug.
 2022-11-20 01:16:52 +00:00
Michael Goulet
c36ff28d42 drive-by: PolyExistentialPredicate 2022-11-19 04:04:27 +00:00
Ralf Jung
99f7e9494e try_normalize_after_erasing_regions: promote an assertion to always run 2022-11-17 09:06:15 +01:00
Oli Scherer
4f11f3b257 Convert predicates into Predicate in the Obligation constructor 2022-11-16 09:25:19 +00:00
Michael Goulet
36a106891a Make rustc build with new chalk 2022-11-13 19:53:44 +00:00
Michael Goulet
6de5f6277e Bump chalk to v0.87 2022-11-13 19:29:38 +00:00
Michael Goulet
63217e08cc make dropck_outlives into a proper canonicalized type query 2022-11-09 22:58:39 +00:00
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
Mateusz
c97fd8183a
Refactor tcx mk_const parameters. 2022-11-04 20:33:32 +00:00
Michael Goulet
2f9794b84a remove _types from ocx method names 2022-10-27 15:43:37 +00:00
Michael Goulet
ce11ae5d0d Address some more nits 2022-10-27 15:43:33 +00:00
Michael Goulet
d793d80cf7 (almost) Always use ObligationCtxt when dealing with canonical queries 2022-10-27 15:43:33 +00:00
lcnr
face090ef1 rm try_normalize_mir_const_after_erasing_regions 2022-10-17 10:54:03 +02:00
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
Oli Scherer
c7b6ebdf7c It's not about types or consts, but the lack of regions 2022-10-04 14:10:44 +00:00
Pietro Albini
3975d55d98
remove cfg(bootstrap) 2022-09-26 10:14:45 +02:00
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
Matthias Krüger
16de1fddee
Rollup merge of #102016 - lcnr:given-OutlivesEnvironment, r=jackh726 
implied_bounds: deal with inference vars

fixes #101951

while computing implied bounds for `<<T as ConstructionFirm>::Builder as BuilderFn<'_>>::Output` normalization replaces a projection with an inference var (adding a `Projection` obligation). Until we prove that obligation, this inference var remains unknown, which caused us to miss an implied bound necessary to prove that the unnormalized projection from the trait method signature is wf.

r? types
 2022-09-25 09:32:07 +02:00
Oli Scherer
37928f5986 Neither require nor imply lifetime bounds on opaque type for well formedness 2022-09-21 13:11:54 +00:00
lcnr
71f8fd5c58 improve infer var handling for implied bounds 2022-09-19 15:13:34 +02:00
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
1eb71f0893 Add back in normalize call 2022-09-17 11:46:04 -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
Jack Huey
e09242d5b8 Final bits 2022-09-16 17:47:53 -04:00