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Nadrierilcuviper
Nadrieril
authored and
cuviper
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Revert warning empty patterns as unreachable
(cherry picked from commit 5b7be14)
1 parent 4976ae4 commit 7410cbf

17 files changed

+86
-447
lines changed

‎compiler/rustc_pattern_analysis/src/usefulness.rs

+5-1
Original file line numberDiff line numberDiff line change
@@ -951,7 +951,11 @@ impl<Cx: PatCx> PlaceInfo<Cx> {
951951
self.is_scrutinee && matches!(ctors_for_ty, ConstructorSet::NoConstructors);
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// Whether empty patterns are counted as useful or not. We only warn an empty arm unreachable if
953953
// it is guaranteed unreachable by the opsem (i.e. if the place is `known_valid`).
954-
let empty_arms_are_unreachable = self.validity.is_known_valid();
954+
// We don't want to warn empty patterns as unreachable by default just yet. We will in a
955+
// later version of rust or under a different lint name, see
956+
// https://github.com/rust-lang/rust/pull/129103.
957+
let empty_arms_are_unreachable = self.validity.is_known_valid()
958+
&& (is_toplevel_exception || cx.is_exhaustive_patterns_feature_on());
955959
// Whether empty patterns can be omitted for exhaustiveness. We ignore place validity in the
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// toplevel exception and `exhaustive_patterns` cases for backwards compatibility.
957961
let can_omit_empty_arms = self.validity.is_known_valid()

‎tests/ui/pattern/usefulness/empty-types.never_pats.stderr

+1-187
Original file line numberDiff line numberDiff line change
@@ -43,30 +43,6 @@ LL + _ => todo!(),
4343
LL + }
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|
4545

46-
error: unreachable pattern
47-
--> $DIR/empty-types.rs:70:9
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|
49-
LL | (_, _) => {}
50-
| ^^^^^^ matches no values because `(u32, !)` is uninhabited
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|
52-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
53-
54-
error: unreachable pattern
55-
--> $DIR/empty-types.rs:76:9
56-
|
57-
LL | _ => {}
58-
| ^ matches no values because `(!, !)` is uninhabited
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|
60-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
61-
62-
error: unreachable pattern
63-
--> $DIR/empty-types.rs:79:9
64-
|
65-
LL | (_, _) => {}
66-
| ^^^^^^ matches no values because `(!, !)` is uninhabited
67-
|
68-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
69-
7046
error: unreachable pattern
7147
--> $DIR/empty-types.rs:83:9
7248
|
@@ -94,22 +70,6 @@ LL + Ok(_) => todo!(),
9470
LL + }
9571
|
9672

97-
error: unreachable pattern
98-
--> $DIR/empty-types.rs:94:9
99-
|
100-
LL | Err(_) => {}
101-
| ^^^^^^ matches no values because `!` is uninhabited
102-
|
103-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
104-
105-
error: unreachable pattern
106-
--> $DIR/empty-types.rs:99:9
107-
|
108-
LL | Err(_) => {}
109-
| ^^^^^^ matches no values because `!` is uninhabited
110-
|
111-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
112-
11373
error[E0004]: non-exhaustive patterns: `Ok(1_u32..=u32::MAX)` not covered
11474
--> $DIR/empty-types.rs:96:11
11575
|
@@ -156,54 +116,6 @@ help: you might want to use `let else` to handle the variant that isn't matched
156116
LL | let Ok(_x) = &res_u32_never else { todo!() };
157117
| ++++++++++++++++
158118

159-
error: unreachable pattern
160-
--> $DIR/empty-types.rs:112:9
161-
|
162-
LL | _ => {}
163-
| ^ matches no values because `Result<!, !>` is uninhabited
164-
|
165-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
166-
167-
error: unreachable pattern
168-
--> $DIR/empty-types.rs:115:9
169-
|
170-
LL | Ok(_) => {}
171-
| ^^^^^ matches no values because `Result<!, !>` is uninhabited
172-
|
173-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
174-
175-
error: unreachable pattern
176-
--> $DIR/empty-types.rs:118:9
177-
|
178-
LL | Ok(_) => {}
179-
| ^^^^^ matches no values because `Result<!, !>` is uninhabited
180-
|
181-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
182-
183-
error: unreachable pattern
184-
--> $DIR/empty-types.rs:119:9
185-
|
186-
LL | _ => {}
187-
| ^ matches no values because `Result<!, !>` is uninhabited
188-
|
189-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
190-
191-
error: unreachable pattern
192-
--> $DIR/empty-types.rs:122:9
193-
|
194-
LL | Ok(_) => {}
195-
| ^^^^^ matches no values because `Result<!, !>` is uninhabited
196-
|
197-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
198-
199-
error: unreachable pattern
200-
--> $DIR/empty-types.rs:123:9
201-
|
202-
LL | Err(_) => {}
203-
| ^^^^^^ matches no values because `Result<!, !>` is uninhabited
204-
|
205-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
206-
207119
error: unreachable pattern
208120
--> $DIR/empty-types.rs:132:13
209121
|
@@ -220,22 +132,6 @@ LL | _ if false => {}
220132
|
221133
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
222134

223-
error: unreachable pattern
224-
--> $DIR/empty-types.rs:143:13
225-
|
226-
LL | Some(_) => {}
227-
| ^^^^^^^ matches no values because `Void` is uninhabited
228-
|
229-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
230-
231-
error: unreachable pattern
232-
--> $DIR/empty-types.rs:147:13
233-
|
234-
LL | None => {}
235-
| ---- matches all the relevant values
236-
LL | _ => {}
237-
| ^ no value can reach this
238-
239135
error[E0004]: non-exhaustive patterns: `Some(!)` not covered
240136
--> $DIR/empty-types.rs:156:15
241137
|
@@ -303,30 +199,6 @@ LL | _ => {}
303199
|
304200
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
305201

306-
error: unreachable pattern
307-
--> $DIR/empty-types.rs:284:9
308-
|
309-
LL | (_, _) => {}
310-
| ^^^^^^ matches no values because `(!, !)` is uninhabited
311-
|
312-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
313-
314-
error: unreachable pattern
315-
--> $DIR/empty-types.rs:287:9
316-
|
317-
LL | Ok(_) => {}
318-
| ^^^^^ matches no values because `Result<!, !>` is uninhabited
319-
|
320-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
321-
322-
error: unreachable pattern
323-
--> $DIR/empty-types.rs:288:9
324-
|
325-
LL | Err(_) => {}
326-
| ^^^^^^ matches no values because `Result<!, !>` is uninhabited
327-
|
328-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
329-
330202
error[E0005]: refutable pattern in local binding
331203
--> $DIR/empty-types.rs:297:13
332204
|
@@ -474,30 +346,6 @@ LL + _ => todo!(),
474346
LL + }
475347
|
476348

477-
error: unreachable pattern
478-
--> $DIR/empty-types.rs:368:9
479-
|
480-
LL | _ => {}
481-
| ^ matches no values because `[!; 3]` is uninhabited
482-
|
483-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
484-
485-
error: unreachable pattern
486-
--> $DIR/empty-types.rs:371:9
487-
|
488-
LL | [_, _, _] => {}
489-
| ^^^^^^^^^ matches no values because `[!; 3]` is uninhabited
490-
|
491-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
492-
493-
error: unreachable pattern
494-
--> $DIR/empty-types.rs:374:9
495-
|
496-
LL | [_, ..] => {}
497-
| ^^^^^^^ matches no values because `[!; 3]` is uninhabited
498-
|
499-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
500-
501349
error[E0004]: non-exhaustive patterns: type `[!; 0]` is non-empty
502350
--> $DIR/empty-types.rs:388:11
503351
|
@@ -534,40 +382,6 @@ LL ~ [..] if false => {},
534382
LL + [] => todo!()
535383
|
536384

537-
error: unreachable pattern
538-
--> $DIR/empty-types.rs:416:9
539-
|
540-
LL | Some(_) => {}
541-
| ^^^^^^^ matches no values because `!` is uninhabited
542-
|
543-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
544-
545-
error: unreachable pattern
546-
--> $DIR/empty-types.rs:421:9
547-
|
548-
LL | Some(_a) => {}
549-
| ^^^^^^^^ matches no values because `!` is uninhabited
550-
|
551-
= note: to learn more about uninhabited types, see https://doc.rust-lang.org/nomicon/exotic-sizes.html#empty-types
552-
553-
error: unreachable pattern
554-
--> $DIR/empty-types.rs:426:9
555-
|
556-
LL | None => {}
557-
| ---- matches all the relevant values
558-
LL | // !useful, !reachable
559-
LL | _ => {}
560-
| ^ no value can reach this
561-
562-
error: unreachable pattern
563-
--> $DIR/empty-types.rs:431:9
564-
|
565-
LL | None => {}
566-
| ---- matches all the relevant values
567-
LL | // !useful, !reachable
568-
LL | _a => {}
569-
| ^^ no value can reach this
570-
571385
error[E0004]: non-exhaustive patterns: `&Some(!)` not covered
572386
--> $DIR/empty-types.rs:451:11
573387
|
@@ -744,7 +558,7 @@ LL ~ None => {},
744558
LL + Some(!)
745559
|
746560

747-
error: aborting due to 65 previous errors; 1 warning emitted
561+
error: aborting due to 42 previous errors; 1 warning emitted
748562

749563
Some errors have detailed explanations: E0004, E0005.
750564
For more information about an error, try `rustc --explain E0004`.

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