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diannedianne
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best_blame_constraint: avoid blaming assignments without user-provided types
1 parent 41cbb95 commit b041c50

16 files changed

+83
-59
lines changed

‎compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -2911,7 +2911,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
29112911
(
29122912
name,
29132913
BorrowExplanation::MustBeValidFor {
2914-
category: ConstraintCategory::Assignment,
2914+
category: ConstraintCategory::Assignment { .. },
29152915
from_closure: false,
29162916
region_name:
29172917
RegionName {

‎compiler/rustc_borrowck/src/diagnostics/region_errors.rs

+3-3
Original file line numberDiff line numberDiff line change
@@ -41,7 +41,7 @@ impl<'tcx> ConstraintDescription for ConstraintCategory<'tcx> {
4141
fn description(&self) -> &'static str {
4242
// Must end with a space. Allows for empty names to be provided.
4343
match self {
44-
ConstraintCategory::Assignment => "assignment ",
44+
ConstraintCategory::Assignment { .. } => "assignment ",
4545
ConstraintCategory::Return(_) => "returning this value ",
4646
ConstraintCategory::Yield => "yielding this value ",
4747
ConstraintCategory::UseAsConst => "using this value as a constant ",
@@ -481,7 +481,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
481481
(ConstraintCategory::Return(kind), true, false) if self.is_closure_fn_mut(fr) => {
482482
self.report_fnmut_error(&errci, kind)
483483
}
484-
(ConstraintCategory::Assignment, true, false)
484+
(ConstraintCategory::Assignment { .. }, true, false)
485485
| (ConstraintCategory::CallArgument(_), true, false) => {
486486
let mut db = self.report_escaping_data_error(&errci);
487487

@@ -672,7 +672,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
672672
// Revert to the normal error in these cases.
673673
// Assignments aren't "escapes" in function items.
674674
if (fr_name_and_span.is_none() && outlived_fr_name_and_span.is_none())
675-
|| (*category == ConstraintCategory::Assignment
675+
|| (matches!(category, ConstraintCategory::Assignment { .. })
676676
&& self.regioncx.universal_regions().defining_ty.is_fn_def())
677677
|| self.regioncx.universal_regions().defining_ty.is_const()
678678
{

‎compiler/rustc_borrowck/src/region_infer/mod.rs

+1
Original file line numberDiff line numberDiff line change
@@ -2023,6 +2023,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
20232023
| ConstraintCategory::BoringNoLocation
20242024
| ConstraintCategory::Internal
20252025
| ConstraintCategory::Predicate(_)
2026+
| ConstraintCategory::Assignment { has_interesting_ty: false }
20262027
) && constraint.span.desugaring_kind().is_none_or(|kind| {
20272028
// Try to avoid blaming constraints from desugarings, since they may not clearly
20282029
// clearly match what users have written. As an exception, allow blaming returns

‎compiler/rustc_borrowck/src/type_check/mod.rs

+14-2
Original file line numberDiff line numberDiff line change
@@ -1135,7 +1135,18 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
11351135
Some(l) if !body.local_decls[l].is_user_variable() => {
11361136
ConstraintCategory::Boring
11371137
}
1138-
_ => ConstraintCategory::Assignment,
1138+
Some(l) => ConstraintCategory::Assignment {
1139+
has_interesting_ty: body.local_decls[l].user_ty.is_some()
1140+
|| matches!(
1141+
body.local_decls[l].local_info(),
1142+
LocalInfo::User(BindingForm::Var(VarBindingForm {
1143+
opt_ty_info: Some(_),
1144+
..
1145+
}))
1146+
),
1147+
},
1148+
// Assignments to projections should be considered interesting.
1149+
_ => ConstraintCategory::Assignment { has_interesting_ty: true },
11391150
};
11401151
debug!(
11411152
"assignment category: {:?} {:?}",
@@ -1469,7 +1480,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
14691480
Some(l) if !body.local_decls[l].is_user_variable() => {
14701481
ConstraintCategory::Boring
14711482
}
1472-
_ => ConstraintCategory::Assignment,
1483+
// The return type of a call is interesting for diagnostics.
1484+
_ => ConstraintCategory::Assignment { has_interesting_ty: true },
14731485
};
14741486

14751487
let locations = term_location.to_locations();

‎compiler/rustc_middle/src/mir/query.rs

+6-1
Original file line numberDiff line numberDiff line change
@@ -250,7 +250,12 @@ pub enum ConstraintCategory<'tcx> {
250250
CallArgument(#[derive_where(skip)] Option<Ty<'tcx>>),
251251
CopyBound,
252252
SizedBound,
253-
Assignment,
253+
Assignment {
254+
/// Whether this assignment is likely to be interesting to refer to in diagnostics.
255+
/// Currently, this is true when it's assigning to a projection, when it's assigning from
256+
/// the return value of a call, and when it has a user-provided type annotation.
257+
has_interesting_ty: bool,
258+
},
254259
/// A constraint that came from a usage of a variable (e.g. in an ADT expression
255260
/// like `Foo { field: my_val }`)
256261
Usage,

‎tests/ui/fn/fn_def_coercion.rs

+2-2
Original file line numberDiff line numberDiff line change
@@ -46,12 +46,12 @@ fn j<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
4646

4747
fn k<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
4848
let x = match true {
49-
true => foo::<&'c ()>, //~ ERROR lifetime may not live long enough
49+
true => foo::<&'c ()>,
5050
false => foo::<&'a ()>, //~ ERROR lifetime may not live long enough
5151
};
5252

5353
x(a);
54-
x(b);
54+
x(b); //~ ERROR lifetime may not live long enough
5555
x(c);
5656
}
5757

‎tests/ui/fn/fn_def_coercion.stderr

+19-22
Original file line numberDiff line numberDiff line change
@@ -6,9 +6,9 @@ LL | fn f<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
66
| |
77
| lifetime `'a` defined here
88
LL | let mut x = foo::<&'a ()>;
9-
| ^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
9+
| ^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'b`
1010
|
11-
= help: consider adding the following bound: `'b: 'a`
11+
= help: consider adding the following bound: `'a: 'b`
1212
= note: requirement occurs because of a function pointer to `foo`
1313
= note: the function `foo` is invariant over the parameter `T`
1414
= help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
@@ -22,9 +22,9 @@ LL | fn f<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
2222
| lifetime `'a` defined here
2323
LL | let mut x = foo::<&'a ()>;
2424
LL | x = foo::<&'b ()>;
25-
| ^^^^^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'b`
25+
| ^^^^^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
2626
|
27-
= help: consider adding the following bound: `'a: 'b`
27+
= help: consider adding the following bound: `'b: 'a`
2828
= note: requirement occurs because of a function pointer to `foo`
2929
= note: the function `foo` is invariant over the parameter `T`
3030
= help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
@@ -53,9 +53,9 @@ LL | fn i<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
5353
| lifetime `'a` defined here
5454
LL | let mut x = foo::<&'c ()>;
5555
LL | x = foo::<&'b ()>;
56-
| ^^^^^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'b`
56+
| ^^^^^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
5757
|
58-
= help: consider adding the following bound: `'a: 'b`
58+
= help: consider adding the following bound: `'b: 'a`
5959
= note: requirement occurs because of a function pointer to `foo`
6060
= note: the function `foo` is invariant over the parameter `T`
6161
= help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
@@ -69,9 +69,9 @@ LL | fn i<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
6969
| lifetime `'a` defined here
7070
...
7171
LL | x = foo::<&'a ()>;
72-
| ^^^^^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
72+
| ^^^^^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'b`
7373
|
74-
= help: consider adding the following bound: `'b: 'a`
74+
= help: consider adding the following bound: `'a: 'b`
7575
= note: requirement occurs because of a function pointer to `foo`
7676
= note: the function `foo` is invariant over the parameter `T`
7777
= help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
@@ -89,9 +89,9 @@ LL | fn j<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
8989
| lifetime `'a` defined here
9090
LL | let x = match true {
9191
LL | true => foo::<&'b ()>,
92-
| ^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'b`
92+
| ^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
9393
|
94-
= help: consider adding the following bound: `'a: 'b`
94+
= help: consider adding the following bound: `'b: 'a`
9595
= note: requirement occurs because of a function pointer to `foo`
9696
= note: the function `foo` is invariant over the parameter `T`
9797
= help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
@@ -105,9 +105,9 @@ LL | fn j<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
105105
| lifetime `'a` defined here
106106
...
107107
LL | false => foo::<&'a ()>,
108-
| ^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
108+
| ^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'b`
109109
|
110-
= help: consider adding the following bound: `'b: 'a`
110+
= help: consider adding the following bound: `'a: 'b`
111111
= note: requirement occurs because of a function pointer to `foo`
112112
= note: the function `foo` is invariant over the parameter `T`
113113
= help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
@@ -117,36 +117,33 @@ help: `'a` and `'b` must be the same: replace one with the other
117117
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
118118

119119
error: lifetime may not live long enough
120-
--> $DIR/fn_def_coercion.rs:49:17
120+
--> $DIR/fn_def_coercion.rs:50:18
121121
|
122122
LL | fn k<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
123123
| -- -- lifetime `'c` defined here
124124
| |
125125
| lifetime `'a` defined here
126-
LL | let x = match true {
127-
LL | true => foo::<&'c ()>,
128-
| ^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'c`
126+
...
127+
LL | false => foo::<&'a ()>,
128+
| ^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'c`
129129
|
130130
= help: consider adding the following bound: `'a: 'c`
131131
= note: requirement occurs because of a function pointer to `foo`
132132
= note: the function `foo` is invariant over the parameter `T`
133133
= help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
134134

135135
error: lifetime may not live long enough
136-
--> $DIR/fn_def_coercion.rs:50:18
136+
--> $DIR/fn_def_coercion.rs:54:5
137137
|
138138
LL | fn k<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
139139
| -- -- lifetime `'b` defined here
140140
| |
141141
| lifetime `'a` defined here
142142
...
143-
LL | false => foo::<&'a ()>,
144-
| ^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
143+
LL | x(b);
144+
| ^^^^ argument requires that `'b` must outlive `'a`
145145
|
146146
= help: consider adding the following bound: `'b: 'a`
147-
= note: requirement occurs because of a function pointer to `foo`
148-
= note: the function `foo` is invariant over the parameter `T`
149-
= help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
150147

151148
help: the following changes may resolve your lifetime errors
152149
|

‎tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,6 @@
11
fn foo(&mut (ref mut v, w): &mut (&u8, &u8), x: &u8) {
2-
//~^ ERROR lifetime may not live long enough
32
*v = x;
3+
//~^ ERROR lifetime may not live long enough
44
}
55

66
fn main() { }

‎tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.stderr

+6-8
Original file line numberDiff line numberDiff line change
@@ -1,15 +1,13 @@
11
error: lifetime may not live long enough
2-
--> $DIR/ex3-both-anon-regions-2.rs:1:14
2+
--> $DIR/ex3-both-anon-regions-2.rs:2:5
33
|
44
LL | fn foo(&mut (ref mut v, w): &mut (&u8, &u8), x: &u8) {
5-
| ^^^^^^^^^ - - let's call the lifetime of this reference `'1`
6-
| | |
7-
| | let's call the lifetime of this reference `'2`
8-
| assignment requires that `'1` must outlive `'2`
5+
| - - let's call the lifetime of this reference `'1`
6+
| |
7+
| let's call the lifetime of this reference `'2`
8+
LL | *v = x;
9+
| ^^^^^^ assignment requires that `'1` must outlive `'2`
910
|
10-
= note: requirement occurs because of a mutable reference to `&u8`
11-
= note: mutable references are invariant over their type parameter
12-
= help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
1311
help: consider introducing a named lifetime parameter
1412
|
1513
LL | fn foo<'a>(&mut (ref mut v, w): &mut (&'a u8, &u8), x: &'a u8) {

‎tests/ui/match/match-ref-mut-invariance.stderr

+2-2
Original file line numberDiff line numberDiff line change
@@ -1,12 +1,12 @@
11
error: lifetime may not live long enough
2-
--> $DIR/match-ref-mut-invariance.rs:10:24
2+
--> $DIR/match-ref-mut-invariance.rs:10:9
33
|
44
LL | impl<'b> S<'b> {
55
| -- lifetime `'b` defined here
66
LL | fn bar<'a>(&'a mut self) -> &'a mut &'a i32 {
77
| -- lifetime `'a` defined here
88
LL | match self.0 { ref mut x => x }
9-
| ^^^^^^^^^ assignment requires that `'a` must outlive `'b`
9+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ method was supposed to return data with lifetime `'b` but it is returning data with lifetime `'a`
1010
|
1111
= help: consider adding the following bound: `'a: 'b`
1212
= note: requirement occurs because of a mutable reference to `&i32`

‎tests/ui/match/match-ref-mut-let-invariance.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -8,8 +8,8 @@ struct S<'b>(&'b i32);
88
impl<'b> S<'b> {
99
fn bar<'a>(&'a mut self) -> &'a mut &'a i32 {
1010
let ref mut x = self.0;
11-
//~^ ERROR lifetime may not live long enough
1211
x
12+
//~^ ERROR lifetime may not live long enough
1313
}
1414
}
1515

‎tests/ui/match/match-ref-mut-let-invariance.stderr

+3-2
Original file line numberDiff line numberDiff line change
@@ -1,12 +1,13 @@
11
error: lifetime may not live long enough
2-
--> $DIR/match-ref-mut-let-invariance.rs:10:13
2+
--> $DIR/match-ref-mut-let-invariance.rs:11:9
33
|
44
LL | impl<'b> S<'b> {
55
| -- lifetime `'b` defined here
66
LL | fn bar<'a>(&'a mut self) -> &'a mut &'a i32 {
77
| -- lifetime `'a` defined here
88
LL | let ref mut x = self.0;
9-
| ^^^^^^^^^ assignment requires that `'a` must outlive `'b`
9+
LL | x
10+
| ^ method was supposed to return data with lifetime `'b` but it is returning data with lifetime `'a`
1011
|
1112
= help: consider adding the following bound: `'a: 'b`
1213
= note: requirement occurs because of a mutable reference to `&i32`

‎tests/ui/nll/user-annotations/adt-tuple-struct-calls.stderr

+12-6
Original file line numberDiff line numberDiff line change
@@ -4,9 +4,11 @@ error[E0597]: `c` does not live long enough
44
LL | let c = 66;
55
| - binding `c` declared here
66
LL | let f = SomeStruct::<&'static u32>;
7-
| -------------------------- assignment requires that `c` is borrowed for `'static`
87
LL | f(&c);
9-
| ^^ borrowed value does not live long enough
8+
| --^^-
9+
| | |
10+
| | borrowed value does not live long enough
11+
| argument requires that `c` is borrowed for `'static`
1012
LL | }
1113
| - `c` dropped here while still borrowed
1214

@@ -18,9 +20,11 @@ LL | fn annot_reference_named_lifetime<'a>(_d: &'a u32) {
1820
LL | let c = 66;
1921
| - binding `c` declared here
2022
LL | let f = SomeStruct::<&'a u32>;
21-
| --------------------- assignment requires that `c` is borrowed for `'a`
2223
LL | f(&c);
23-
| ^^ borrowed value does not live long enough
24+
| --^^-
25+
| | |
26+
| | borrowed value does not live long enough
27+
| argument requires that `c` is borrowed for `'a`
2428
LL | }
2529
| - `c` dropped here while still borrowed
2630

@@ -33,9 +37,11 @@ LL | let _closure = || {
3337
LL | let c = 66;
3438
| - binding `c` declared here
3539
LL | let f = SomeStruct::<&'a u32>;
36-
| --------------------- assignment requires that `c` is borrowed for `'a`
3740
LL | f(&c);
38-
| ^^ borrowed value does not live long enough
41+
| --^^-
42+
| | |
43+
| | borrowed value does not live long enough
44+
| argument requires that `c` is borrowed for `'a`
3945
LL | };
4046
| - `c` dropped here while still borrowed
4147

‎tests/ui/nll/user-annotations/method-ufcs-1.stderr

+4-3
Original file line numberDiff line numberDiff line change
@@ -4,10 +4,11 @@ error[E0597]: `a` does not live long enough
44
LL | let a = 22;
55
| - binding `a` declared here
66
...
7-
LL | let x = <&'static u32 as Bazoom<_>>::method;
8-
| ----------------------------------- assignment requires that `a` is borrowed for `'static`
97
LL | x(&a, b, c);
10-
| ^^ borrowed value does not live long enough
8+
| --^^-------
9+
| | |
10+
| | borrowed value does not live long enough
11+
| argument requires that `a` is borrowed for `'static`
1112
LL | }
1213
| - `a` dropped here while still borrowed
1314

‎tests/ui/nll/user-annotations/method-ufcs-2.stderr

+4-3
Original file line numberDiff line numberDiff line change
@@ -4,10 +4,11 @@ error[E0597]: `a` does not live long enough
44
LL | let a = 22;
55
| - binding `a` declared here
66
...
7-
LL | let x = <&'static u32 as Bazoom<_>>::method;
8-
| ----------------------------------- assignment requires that `a` is borrowed for `'static`
97
LL | x(&a, b, c);
10-
| ^^ borrowed value does not live long enough
8+
| --^^-------
9+
| | |
10+
| | borrowed value does not live long enough
11+
| argument requires that `a` is borrowed for `'static`
1112
LL | }
1213
| - `a` dropped here while still borrowed
1314

‎tests/ui/nll/user-annotations/promoted-annotation.stderr

+4-2
Original file line numberDiff line numberDiff line change
@@ -6,9 +6,11 @@ LL | fn foo<'a>() {
66
LL | let x = 0;
77
| - binding `x` declared here
88
LL | let f = &drop::<&'a i32>;
9-
| ---------------- assignment requires that `x` is borrowed for `'a`
109
LL | f(&x);
11-
| ^^ borrowed value does not live long enough
10+
| --^^-
11+
| | |
12+
| | borrowed value does not live long enough
13+
| argument requires that `x` is borrowed for `'a`
1214
LL |
1315
LL | }
1416
| - `x` dropped here while still borrowed

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