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best_blame_constraint: avoid blaming assignments without user-provided types

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This commit is contained in:
dianne 2024-12-19 01:16:53 -08:00
parent 31e4d8175a
commit 50222dba2e
19 changed files with 88 additions and 64 deletions
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2
compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
View file

@ -2911,7 +2911,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
(
name,
BorrowExplanation::MustBeValidFor {
category: ConstraintCategory::Assignment,
category: ConstraintCategory::Assignment { .. },
from_closure: false,
region_name:
RegionName {

6
compiler/rustc_borrowck/src/diagnostics/region_errors.rs
View file

@ -41,7 +41,7 @@ impl<'tcx> ConstraintDescription for ConstraintCategory<'tcx> {
fn description(&self) -> &'static str {
// Must end with a space. Allows for empty names to be provided.
match self {
ConstraintCategory::Assignment => "assignment ",
ConstraintCategory::Assignment { .. } => "assignment ",
ConstraintCategory::Return(_) => "returning this value ",
ConstraintCategory::Yield => "yielding this value ",
ConstraintCategory::UseAsConst => "using this value as a constant ",
@ -481,7 +481,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
(ConstraintCategory::Return(kind), true, false) if self.is_closure_fn_mut(fr) => {
self.report_fnmut_error(&errci, kind)
}
(ConstraintCategory::Assignment, true, false)
(ConstraintCategory::Assignment { .. }, true, false)
| (ConstraintCategory::CallArgument(_), true, false) => {
let mut db = self.report_escaping_data_error(&errci);
@ -672,7 +672,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
// Revert to the normal error in these cases.
// Assignments aren't "escapes" in function items.
if (fr_name_and_span.is_none() && outlived_fr_name_and_span.is_none())
|| (*category == ConstraintCategory::Assignment
|| (matches!(category, ConstraintCategory::Assignment { .. })
&& self.regioncx.universal_regions().defining_ty.is_fn_def())
|| self.regioncx.universal_regions().defining_ty.is_const()
{

1
compiler/rustc_borrowck/src/region_infer/mod.rs
View file

@ -2034,6 +2034,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
| ConstraintCategory::BoringNoLocation
| ConstraintCategory::Internal
| ConstraintCategory::Predicate(_)
| ConstraintCategory::Assignment { has_interesting_ty: false }
) && constraint.span.desugaring_kind().is_none_or(|kind| {
// Try to avoid blaming constraints from desugarings, since they may not clearly
// clearly match what users have written. As an exception, allow blaming returns

16
compiler/rustc_borrowck/src/type_check/mod.rs
View file

@ -892,7 +892,18 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
Some(l) if !body.local_decls[l].is_user_variable() => {
ConstraintCategory::Boring
}
_ => ConstraintCategory::Assignment,
Some(l) => ConstraintCategory::Assignment {
has_interesting_ty: body.local_decls[l].user_ty.is_some()
|| matches!(
body.local_decls[l].local_info(),
LocalInfo::User(BindingForm::Var(VarBindingForm {
opt_ty_info: Some(_),
..
}))
),
},
// Assignments to projections should be considered interesting.
_ => ConstraintCategory::Assignment { has_interesting_ty: true },
};
debug!(
"assignment category: {:?} {:?}",
@ -1226,7 +1237,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
Some(l) if !body.local_decls[l].is_user_variable() => {
ConstraintCategory::Boring
}
_ => ConstraintCategory::Assignment,
// The return type of a call is interesting for diagnostics.
_ => ConstraintCategory::Assignment { has_interesting_ty: true },
};
let locations = term_location.to_locations();

7
compiler/rustc_middle/src/mir/query.rs
View file

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

4
tests/mir-opt/nll/region_subtyping_basic.main.nll.0.32bit.mir
View file

@ -17,8 +17,8 @@
| '?2 live at {bb1[0]}
| '?3 live at {bb1[1..=3]}
| '?4 live at {bb1[4..=7], bb2[0..=2]}
| '?2: '?3 due to Assignment at Single(bb1[0]) ($DIR/region_subtyping_basic.rs:19:13: 19:18 (#0)
| '?3: '?4 due to Assignment at Single(bb1[3]) ($DIR/region_subtyping_basic.rs:20:13: 20:14 (#0)
| '?2: '?3 due to Assignment { has_interesting_ty: false } at Single(bb1[0]) ($DIR/region_subtyping_basic.rs:19:13: 19:18 (#0)
| '?3: '?4 due to Assignment { has_interesting_ty: false } at Single(bb1[3]) ($DIR/region_subtyping_basic.rs:20:13: 20:14 (#0)
|
| Borrows
| bw0: issued at bb1[0] in '?2

4
tests/mir-opt/nll/region_subtyping_basic.main.nll.0.64bit.mir
View file

@ -17,8 +17,8 @@
| '?2 live at {bb1[0]}
| '?3 live at {bb1[1..=3]}
| '?4 live at {bb1[4..=7], bb2[0..=2]}
| '?2: '?3 due to Assignment at Single(bb1[0]) ($DIR/region_subtyping_basic.rs:19:13: 19:18 (#0)
| '?3: '?4 due to Assignment at Single(bb1[3]) ($DIR/region_subtyping_basic.rs:20:13: 20:14 (#0)
| '?2: '?3 due to Assignment { has_interesting_ty: false } at Single(bb1[0]) ($DIR/region_subtyping_basic.rs:19:13: 19:18 (#0)
| '?3: '?4 due to Assignment { has_interesting_ty: false } at Single(bb1[3]) ($DIR/region_subtyping_basic.rs:20:13: 20:14 (#0)
|
| Borrows
| bw0: issued at bb1[0] in '?2

2
tests/mir-opt/storage_ranges.main.nll.0.mir
View file

@ -15,7 +15,7 @@
| '?1 live at {bb0[0..=22]}
| '?2 live at {bb0[10]}
| '?3 live at {bb0[11]}
| '?2: '?3 due to Assignment at Single(bb0[10]) ($DIR/storage_ranges.rs:7:17: 7:25 (#0)
| '?2: '?3 due to Assignment { has_interesting_ty: false } at Single(bb0[10]) ($DIR/storage_ranges.rs:7:17: 7:25 (#0)
|
| Borrows
| bw0: issued at bb0[10] in '?2

4
tests/ui/fn/fn_def_coercion.rs
View file

@ -46,12 +46,12 @@ fn j<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
fn k<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
let x = match true {
true => foo::<&'c ()>, //~ ERROR lifetime may not live long enough
true => foo::<&'c ()>,
false => foo::<&'a ()>, //~ ERROR lifetime may not live long enough
};
x(a);
x(b);
x(b); //~ ERROR lifetime may not live long enough
x(c);
}

41
tests/ui/fn/fn_def_coercion.stderr
View file

@ -6,9 +6,9 @@ LL | fn f<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
| |
| lifetime `'a` defined here
LL | let mut x = foo::<&'a ()>;
| ^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
| ^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'b`
|
= help: consider adding the following bound: `'b: 'a`
= help: consider adding the following bound: `'a: 'b`
= note: requirement occurs because of a function pointer to `foo`
= note: the function `foo` is invariant over the parameter `T`
= 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 ()) {
| lifetime `'a` defined here
LL | let mut x = foo::<&'a ()>;
LL | x = foo::<&'b ()>;
| ^^^^^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'b`
| ^^^^^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
|
= help: consider adding the following bound: `'a: 'b`
= help: consider adding the following bound: `'b: 'a`
= note: requirement occurs because of a function pointer to `foo`
= note: the function `foo` is invariant over the parameter `T`
= 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 ()) {
| lifetime `'a` defined here
LL | let mut x = foo::<&'c ()>;
LL | x = foo::<&'b ()>;
| ^^^^^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'b`
| ^^^^^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
|
= help: consider adding the following bound: `'a: 'b`
= help: consider adding the following bound: `'b: 'a`
= note: requirement occurs because of a function pointer to `foo`
= note: the function `foo` is invariant over the parameter `T`
= 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 ()) {
| lifetime `'a` defined here
...
LL | x = foo::<&'a ()>;
| ^^^^^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
| ^^^^^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'b`
|
= help: consider adding the following bound: `'b: 'a`
= help: consider adding the following bound: `'a: 'b`
= note: requirement occurs because of a function pointer to `foo`
= note: the function `foo` is invariant over the parameter `T`
= 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 ()) {
| lifetime `'a` defined here
LL | let x = match true {
LL | true => foo::<&'b ()>,
| ^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'b`
| ^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
|
= help: consider adding the following bound: `'a: 'b`
= help: consider adding the following bound: `'b: 'a`
= note: requirement occurs because of a function pointer to `foo`
= note: the function `foo` is invariant over the parameter `T`
= 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 ()) {
| lifetime `'a` defined here
...
LL | false => foo::<&'a ()>,
| ^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
| ^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'b`
|
= help: consider adding the following bound: `'b: 'a`
= help: consider adding the following bound: `'a: 'b`
= note: requirement occurs because of a function pointer to `foo`
= note: the function `foo` is invariant over the parameter `T`
= help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
@ -117,15 +117,15 @@ help: `'a` and `'b` must be the same: replace one with the other
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
error: lifetime may not live long enough
--> $DIR/fn_def_coercion.rs:49:17
--> $DIR/fn_def_coercion.rs:50:18
|
LL | fn k<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
| -- -- lifetime `'c` defined here
| |
| lifetime `'a` defined here
LL | let x = match true {
LL | true => foo::<&'c ()>,
| ^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'c`
...
LL | false => foo::<&'a ()>,
| ^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'c`
|
= help: consider adding the following bound: `'a: 'c`
= note: requirement occurs because of a function pointer to `foo`
@ -133,20 +133,17 @@ LL | true => foo::<&'c ()>,
= help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
error: lifetime may not live long enough
--> $DIR/fn_def_coercion.rs:50:18
--> $DIR/fn_def_coercion.rs:54:5
|
LL | fn k<'a, 'b, 'c: 'a + 'b>(a: &'a (), b: &'b (), c: &'c ()) {
| -- -- lifetime `'b` defined here
| |
| lifetime `'a` defined here
...
LL | false => foo::<&'a ()>,
| ^^^^^^^^^^^^^ assignment requires that `'b` must outlive `'a`
LL | x(b);
| ^^^^ argument requires that `'b` must outlive `'a`
|
= help: consider adding the following bound: `'b: 'a`
= note: requirement occurs because of a function pointer to `foo`
= note: the function `foo` is invariant over the parameter `T`
= help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
help: the following changes may resolve your lifetime errors
|

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

@ -1,6 +1,6 @@
fn foo(&mut (ref mut v, w): &mut (&u8, &u8), x: &u8) {
//~^ ERROR lifetime may not live long enough
*v = x;
//~^ ERROR lifetime may not live long enough
}
fn main() { }

14
tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.stderr
View file

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

4
tests/ui/match/match-ref-mut-invariance.stderr
View file

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

2
tests/ui/match/match-ref-mut-let-invariance.rs
View file

@ -8,8 +8,8 @@ struct S<'b>(&'b i32);
impl<'b> S<'b> {
fn bar<'a>(&'a mut self) -> &'a mut &'a i32 {
let ref mut x = self.0;
//~^ ERROR lifetime may not live long enough
x
//~^ ERROR lifetime may not live long enough
}
}

5
tests/ui/match/match-ref-mut-let-invariance.stderr
View file

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

18
tests/ui/nll/user-annotations/adt-tuple-struct-calls.stderr
View file

@ -4,9 +4,11 @@ error[E0597]: `c` does not live long enough
LL | let c = 66;
| - binding `c` declared here
LL | let f = SomeStruct::<&'static u32>;
| -------------------------- assignment requires that `c` is borrowed for `'static`
LL | f(&c);
| ^^ borrowed value does not live long enough
| --^^-
| | |
| | borrowed value does not live long enough
| argument requires that `c` is borrowed for `'static`
LL | }
| - `c` dropped here while still borrowed
@ -18,9 +20,11 @@ LL | fn annot_reference_named_lifetime<'a>(_d: &'a u32) {
LL | let c = 66;
| - binding `c` declared here
LL | let f = SomeStruct::<&'a u32>;
| --------------------- assignment requires that `c` is borrowed for `'a`
LL | f(&c);
| ^^ borrowed value does not live long enough
| --^^-
| | |
| | borrowed value does not live long enough
| argument requires that `c` is borrowed for `'a`
LL | }
| - `c` dropped here while still borrowed
@ -33,9 +37,11 @@ LL | let _closure = || {
LL | let c = 66;
| - binding `c` declared here
LL | let f = SomeStruct::<&'a u32>;
| --------------------- assignment requires that `c` is borrowed for `'a`
LL | f(&c);
| ^^ borrowed value does not live long enough
| --^^-
| | |
| | borrowed value does not live long enough
| argument requires that `c` is borrowed for `'a`
LL | };
| - `c` dropped here while still borrowed

7
tests/ui/nll/user-annotations/method-ufcs-1.stderr
View file

@ -4,10 +4,11 @@ error[E0597]: `a` does not live long enough
LL | let a = 22;
| - binding `a` declared here
...
LL | let x = <&'static u32 as Bazoom<_>>::method;
| ----------------------------------- assignment requires that `a` is borrowed for `'static`
LL | x(&a, b, c);
| ^^ borrowed value does not live long enough
| --^^-------
| | |
| | borrowed value does not live long enough
| argument requires that `a` is borrowed for `'static`
LL | }
| - `a` dropped here while still borrowed

7
tests/ui/nll/user-annotations/method-ufcs-2.stderr
View file

@ -4,10 +4,11 @@ error[E0597]: `a` does not live long enough
LL | let a = 22;
| - binding `a` declared here
...
LL | let x = <&'static u32 as Bazoom<_>>::method;
| ----------------------------------- assignment requires that `a` is borrowed for `'static`
LL | x(&a, b, c);
| ^^ borrowed value does not live long enough
| --^^-------
| | |
| | borrowed value does not live long enough
| argument requires that `a` is borrowed for `'static`
LL | }
| - `a` dropped here while still borrowed

6
tests/ui/nll/user-annotations/promoted-annotation.stderr
View file

@ -6,9 +6,11 @@ LL | fn foo<'a>() {
LL | let x = 0;
| - binding `x` declared here
LL | let f = &drop::<&'a i32>;
| ---------------- assignment requires that `x` is borrowed for `'a`
LL | f(&x);
| ^^ borrowed value does not live long enough
| --^^-
| | |
| | borrowed value does not live long enough
| argument requires that `x` is borrowed for `'a`
LL |
LL | }
| - `x` dropped here while still borrowed