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Suggest adding a new lifetime parameter when two elided lifetimes should match up for traits and impls.
Issue #94462
1 parent 97cde9f commit abcccc9

11 files changed

+258
-52
lines changed

‎compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs

Lines changed: 48 additions & 52 deletions
Original file line numberDiff line numberDiff line change
@@ -166,59 +166,55 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
166166
if lifetime_sub.name.is_elided() && lifetime_sup.name.is_elided() {
167167
if let Some(anon_reg) = self.tcx().is_suitable_region(sub) {
168168
let hir_id = self.tcx().hir().local_def_id_to_hir_id(anon_reg.def_id);
169-
if let hir::Node::Item(&hir::Item {
170-
kind: hir::ItemKind::Fn(_, ref generics, ..),
171-
..
172-
}) = self.tcx().hir().get(hir_id)
173-
{
174-
let (suggestion_param_name, introduce_new) = generics
175-
.params
176-
.iter()
177-
.find(|p| matches!(p.kind, GenericParamKind::Lifetime { .. }))
178-
.and_then(|p| self.tcx().sess.source_map().span_to_snippet(p.span).ok())
179-
.map(|name| (name, false))
180-
.unwrap_or_else(|| ("'a".to_string(), true));
181-
182-
let mut suggestions = vec![
183-
if let hir::LifetimeName::Underscore = lifetime_sub.name {
184-
(lifetime_sub.span, suggestion_param_name.clone())
185-
} else {
186-
(
187-
lifetime_sub.span.shrink_to_hi(),
188-
suggestion_param_name.clone() + " ",
189-
)
190-
},
191-
if let hir::LifetimeName::Underscore = lifetime_sup.name {
192-
(lifetime_sup.span, suggestion_param_name.clone())
193-
} else {
194-
(
195-
lifetime_sup.span.shrink_to_hi(),
196-
suggestion_param_name.clone() + " ",
197-
)
198-
},
199-
];
200-
201-
if introduce_new {
202-
let new_param_suggestion = match &generics.params {
203-
[] => (generics.span, format!("<{}>", suggestion_param_name)),
204-
[first, ..] => (
205-
first.span.shrink_to_lo(),
206-
format!("{}, ", suggestion_param_name),
207-
),
208-
};
209-
210-
suggestions.push(new_param_suggestion);
211-
}
212-
213-
err.multipart_suggestion(
214-
"consider introducing a named lifetime parameter",
215-
suggestions,
216-
Applicability::MaybeIncorrect,
217-
);
218-
err.note(
219-
"each elided lifetime in input position becomes a distinct lifetime",
220-
);
169+
170+
let generics = match self.tcx().hir().get(hir_id) {
171+
hir::Node::Item(&hir::Item {
172+
kind: hir::ItemKind::Fn(_, ref generics, ..),
173+
..
174+
})
175+
| hir::Node::TraitItem(&hir::TraitItem { ref generics, .. })
176+
| hir::Node::ImplItem(&hir::ImplItem { ref generics, .. }) => generics,
177+
_ => return,
178+
};
179+
180+
let (suggestion_param_name, introduce_new) = generics
181+
.params
182+
.iter()
183+
.find(|p| matches!(p.kind, GenericParamKind::Lifetime { .. }))
184+
.and_then(|p| self.tcx().sess.source_map().span_to_snippet(p.span).ok())
185+
.map(|name| (name, false))
186+
.unwrap_or_else(|| ("'a".to_string(), true));
187+
188+
let mut suggestions = vec![
189+
if let hir::LifetimeName::Underscore = lifetime_sub.name {
190+
(lifetime_sub.span, suggestion_param_name.clone())
191+
} else {
192+
(lifetime_sub.span.shrink_to_hi(), suggestion_param_name.clone() + " ")
193+
},
194+
if let hir::LifetimeName::Underscore = lifetime_sup.name {
195+
(lifetime_sup.span, suggestion_param_name.clone())
196+
} else {
197+
(lifetime_sup.span.shrink_to_hi(), suggestion_param_name.clone() + " ")
198+
},
199+
];
200+
201+
if introduce_new {
202+
let new_param_suggestion = match &generics.params {
203+
[] => (generics.span, format!("<{}>", suggestion_param_name)),
204+
[first, ..] => {
205+
(first.span.shrink_to_lo(), format!("{}, ", suggestion_param_name))
206+
}
207+
};
208+
209+
suggestions.push(new_param_suggestion);
221210
}
211+
212+
err.multipart_suggestion(
213+
"consider introducing a named lifetime parameter",
214+
suggestions,
215+
Applicability::MaybeIncorrect,
216+
);
217+
err.note("each elided lifetime in input position becomes a distinct lifetime");
222218
}
223219
}
224220
}

‎src/test/ui/issues/issue-17728.stderr

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -8,6 +8,12 @@ LL | fn attemptTraverse(&self, room: &Room, directionStr: &str) -> Result<&R
88
...
99
LL | Some(entry) => Ok(entry),
1010
| ^^^^^^^^^ ...but data from `room` is returned here
11+
|
12+
= note: each elided lifetime in input position becomes a distinct lifetime
13+
help: consider introducing a named lifetime parameter
14+
|
15+
LL | fn attemptTraverse<'a>(&'a self, room: &'a Room, directionStr: &str) -> Result<&Room, &str> {
16+
| ++++ ++ ++
1117

1218
error[E0308]: `match` arms have incompatible types
1319
--> $DIR/issue-17728.rs:109:14

‎src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-return-type-is-anon.stderr

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -7,6 +7,12 @@ LL | fn foo<'a>(&self, x: &i32) -> &i32 {
77
| this parameter and the return type are declared with different lifetimes...
88
LL | x
99
| ^ ...but data from `x` is returned here
10+
|
11+
= note: each elided lifetime in input position becomes a distinct lifetime
12+
help: consider introducing a named lifetime parameter
13+
|
14+
LL | fn foo<'a>(&'a self, x: &'a i32) -> &i32 {
15+
| ++ ++
1016

1117
error: aborting due to previous error
1218

‎src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-self-is-anon.stderr

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -7,6 +7,12 @@ LL | fn foo<'a>(&self, x: &Foo) -> &Foo {
77
| this parameter and the return type are declared with different lifetimes...
88
LL | if true { x } else { self }
99
| ^ ...but data from `x` is returned here
10+
|
11+
= note: each elided lifetime in input position becomes a distinct lifetime
12+
help: consider introducing a named lifetime parameter
13+
|
14+
LL | fn foo<'a>(&'a self, x: &'a Foo) -> &Foo {
15+
| ++ ++
1016

1117
error: aborting due to previous error
1218

‎src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-impl-items.stderr

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -5,6 +5,12 @@ LL | fn foo(x: &mut Vec<&u8>, y: &u8) {
55
| --- --- these two types are declared with different lifetimes...
66
LL | x.push(y);
77
| ^ ...but data from `y` flows into `x` here
8+
|
9+
= note: each elided lifetime in input position becomes a distinct lifetime
10+
help: consider introducing a named lifetime parameter
11+
|
12+
LL | fn foo<'a>(x: &mut Vec<&'a u8>, y: &'a u8) {
13+
| ++++ ++ ++
814

915
error: aborting due to previous error
1016

‎src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch.stderr

Lines changed: 12 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -5,6 +5,12 @@ LL | fn a(self: Pin<&Foo>, f: &Foo) -> &Foo { f }
55
| ---- ---- ^ ...but data from `f` is returned here
66
| |
77
| this parameter and the return type are declared with different lifetimes...
8+
|
9+
= note: each elided lifetime in input position becomes a distinct lifetime
10+
help: consider introducing a named lifetime parameter
11+
|
12+
LL | fn a<'a>(self: Pin<&'a Foo>, f: &'a Foo) -> &Foo { f }
13+
| ++++ ++ ++
814

915
error[E0623]: lifetime mismatch
1016
--> $DIR/arbitrary_self_types_pin_lifetime_mismatch.rs:8:76
@@ -13,6 +19,12 @@ LL | fn c(self: Pin<&Self>, f: &Foo, g: &Foo) -> (Pin<&Foo>, &Foo) { (self,
1319
| ---- ----------------- ^ ...but data from `f` is returned here
1420
| |
1521
| this parameter and the return type are declared with different lifetimes...
22+
|
23+
= note: each elided lifetime in input position becomes a distinct lifetime
24+
help: consider introducing a named lifetime parameter
25+
|
26+
LL | fn c<'a>(self: Pin<&'a Self>, f: &'a Foo, g: &Foo) -> (Pin<&Foo>, &Foo) { (self, f) }
27+
| ++++ ++ ++
1628

1729
error[E0623]: lifetime mismatch
1830
--> $DIR/arbitrary_self_types_pin_lifetime_mismatch.rs:13:58

‎src/test/ui/self/elision/lt-ref-self.stderr

Lines changed: 36 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -7,6 +7,12 @@ LL | fn ref_self(&self, f: &u32) -> &u32 {
77
| this parameter and the return type are declared with different lifetimes...
88
LL | f
99
| ^ ...but data from `f` is returned here
10+
|
11+
= note: each elided lifetime in input position becomes a distinct lifetime
12+
help: consider introducing a named lifetime parameter
13+
|
14+
LL | fn ref_self<'a>(&'a self, f: &'a u32) -> &u32 {
15+
| ++++ ++ ++
1016

1117
error[E0623]: lifetime mismatch
1218
--> $DIR/lt-ref-self.rs:17:9
@@ -17,6 +23,12 @@ LL | fn ref_Self(self: &Self, f: &u32) -> &u32 {
1723
| this parameter and the return type are declared with different lifetimes...
1824
LL | f
1925
| ^ ...but data from `f` is returned here
26+
|
27+
= note: each elided lifetime in input position becomes a distinct lifetime
28+
help: consider introducing a named lifetime parameter
29+
|
30+
LL | fn ref_Self<'a>(self: &'a Self, f: &'a u32) -> &u32 {
31+
| ++++ ++ ++
2032

2133
error[E0623]: lifetime mismatch
2234
--> $DIR/lt-ref-self.rs:21:9
@@ -27,6 +39,12 @@ LL | fn box_ref_Self(self: Box<&Self>, f: &u32) -> &u32 {
2739
| this parameter and the return type are declared with different lifetimes...
2840
LL | f
2941
| ^ ...but data from `f` is returned here
42+
|
43+
= note: each elided lifetime in input position becomes a distinct lifetime
44+
help: consider introducing a named lifetime parameter
45+
|
46+
LL | fn box_ref_Self<'a>(self: Box<&'a Self>, f: &'a u32) -> &u32 {
47+
| ++++ ++ ++
3048

3149
error[E0623]: lifetime mismatch
3250
--> $DIR/lt-ref-self.rs:25:9
@@ -37,6 +55,12 @@ LL | fn pin_ref_Self(self: Pin<&Self>, f: &u32) -> &u32 {
3755
| this parameter and the return type are declared with different lifetimes...
3856
LL | f
3957
| ^ ...but data from `f` is returned here
58+
|
59+
= note: each elided lifetime in input position becomes a distinct lifetime
60+
help: consider introducing a named lifetime parameter
61+
|
62+
LL | fn pin_ref_Self<'a>(self: Pin<&'a Self>, f: &'a u32) -> &u32 {
63+
| ++++ ++ ++
4064

4165
error[E0623]: lifetime mismatch
4266
--> $DIR/lt-ref-self.rs:29:9
@@ -47,6 +71,12 @@ LL | fn box_box_ref_Self(self: Box<Box<&Self>>, f: &u32) -> &u32 {
4771
| this parameter and the return type are declared with different lifetimes...
4872
LL | f
4973
| ^ ...but data from `f` is returned here
74+
|
75+
= note: each elided lifetime in input position becomes a distinct lifetime
76+
help: consider introducing a named lifetime parameter
77+
|
78+
LL | fn box_box_ref_Self<'a>(self: Box<Box<&'a Self>>, f: &'a u32) -> &u32 {
79+
| ++++ ++ ++
5080

5181
error[E0623]: lifetime mismatch
5282
--> $DIR/lt-ref-self.rs:33:9
@@ -57,6 +87,12 @@ LL | fn box_pin_Self(self: Box<Pin<&Self>>, f: &u32) -> &u32 {
5787
| this parameter and the return type are declared with different lifetimes...
5888
LL | f
5989
| ^ ...but data from `f` is returned here
90+
|
91+
= note: each elided lifetime in input position becomes a distinct lifetime
92+
help: consider introducing a named lifetime parameter
93+
|
94+
LL | fn box_pin_Self<'a>(self: Box<Pin<&'a Self>>, f: &'a u32) -> &u32 {
95+
| ++++ ++ ++
6096

6197
error: aborting due to 6 previous errors
6298

‎src/test/ui/self/elision/ref-mut-self.stderr

Lines changed: 36 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -7,6 +7,12 @@ LL | fn ref_self(&mut self, f: &u32) -> &u32 {
77
| this parameter and the return type are declared with different lifetimes...
88
LL | f
99
| ^ ...but data from `f` is returned here
10+
|
11+
= note: each elided lifetime in input position becomes a distinct lifetime
12+
help: consider introducing a named lifetime parameter
13+
|
14+
LL | fn ref_self<'a>(&'a mut self, f: &'a u32) -> &u32 {
15+
| ++++ ++ ++
1016

1117
error[E0623]: lifetime mismatch
1218
--> $DIR/ref-mut-self.rs:17:9
@@ -17,6 +23,12 @@ LL | fn ref_Self(self: &mut Self, f: &u32) -> &u32 {
1723
| this parameter and the return type are declared with different lifetimes...
1824
LL | f
1925
| ^ ...but data from `f` is returned here
26+
|
27+
= note: each elided lifetime in input position becomes a distinct lifetime
28+
help: consider introducing a named lifetime parameter
29+
|
30+
LL | fn ref_Self<'a>(self: &'a mut Self, f: &'a u32) -> &u32 {
31+
| ++++ ++ ++
2032

2133
error[E0623]: lifetime mismatch
2234
--> $DIR/ref-mut-self.rs:21:9
@@ -27,6 +39,12 @@ LL | fn box_ref_Self(self: Box<&mut Self>, f: &u32) -> &u32 {
2739
| this parameter and the return type are declared with different lifetimes...
2840
LL | f
2941
| ^ ...but data from `f` is returned here
42+
|
43+
= note: each elided lifetime in input position becomes a distinct lifetime
44+
help: consider introducing a named lifetime parameter
45+
|
46+
LL | fn box_ref_Self<'a>(self: Box<&'a mut Self>, f: &'a u32) -> &u32 {
47+
| ++++ ++ ++
3048

3149
error[E0623]: lifetime mismatch
3250
--> $DIR/ref-mut-self.rs:25:9
@@ -37,6 +55,12 @@ LL | fn pin_ref_Self(self: Pin<&mut Self>, f: &u32) -> &u32 {
3755
| this parameter and the return type are declared with different lifetimes...
3856
LL | f
3957
| ^ ...but data from `f` is returned here
58+
|
59+
= note: each elided lifetime in input position becomes a distinct lifetime
60+
help: consider introducing a named lifetime parameter
61+
|
62+
LL | fn pin_ref_Self<'a>(self: Pin<&'a mut Self>, f: &'a u32) -> &u32 {
63+
| ++++ ++ ++
4064

4165
error[E0623]: lifetime mismatch
4266
--> $DIR/ref-mut-self.rs:29:9
@@ -47,6 +71,12 @@ LL | fn box_box_ref_Self(self: Box<Box<&mut Self>>, f: &u32) -> &u32 {
4771
| this parameter and the return type are declared with different lifetimes...
4872
LL | f
4973
| ^ ...but data from `f` is returned here
74+
|
75+
= note: each elided lifetime in input position becomes a distinct lifetime
76+
help: consider introducing a named lifetime parameter
77+
|
78+
LL | fn box_box_ref_Self<'a>(self: Box<Box<&'a mut Self>>, f: &'a u32) -> &u32 {
79+
| ++++ ++ ++
5080

5181
error[E0623]: lifetime mismatch
5282
--> $DIR/ref-mut-self.rs:33:9
@@ -57,6 +87,12 @@ LL | fn box_pin_ref_Self(self: Box<Pin<&mut Self>>, f: &u32) -> &u32 {
5787
| this parameter and the return type are declared with different lifetimes...
5888
LL | f
5989
| ^ ...but data from `f` is returned here
90+
|
91+
= note: each elided lifetime in input position becomes a distinct lifetime
92+
help: consider introducing a named lifetime parameter
93+
|
94+
LL | fn box_pin_ref_Self<'a>(self: Box<Pin<&'a mut Self>>, f: &'a u32) -> &u32 {
95+
| ++++ ++ ++
6096

6197
error: aborting due to 6 previous errors
6298

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