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Rollup merge of #98603 - compiler-errors:minor-borrowck-diagnostic-fixes, r=davidtwco
Some borrowck diagnostic fixes 1. Remove some redundant `.as_ref` suggestion logic from borrowck, this has the consequence of also not suggesting `.as_ref` after `Option` methods, but (correctly) before. 2. Fix a bug where we were replacing a binding's name with a type. Instead, make it a note. This is somewhat incomplete. See `src/test/ui/borrowck/suggest-as-ref-on-mut-closure.rs` for more improvements.
2 parents 021d21c + 8fd7356 commit 25fb2b4

16 files changed

+150
-97
lines changed

‎compiler/rustc_borrowck/src/diagnostics/move_errors.rs

Lines changed: 7 additions & 46 deletions
Original file line numberDiff line numberDiff line change
@@ -4,7 +4,7 @@ use rustc_middle::ty;
44
use rustc_mir_dataflow::move_paths::{
55
IllegalMoveOrigin, IllegalMoveOriginKind, LookupResult, MoveError, MovePathIndex,
66
};
7-
use rustc_span::{sym, Span};
7+
use rustc_span::Span;
88

99
use crate::diagnostics::UseSpans;
1010
use crate::prefixes::PrefixSet;
@@ -218,29 +218,13 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
218218

219219
fn report(&mut self, error: GroupedMoveError<'tcx>) {
220220
let (mut err, err_span) = {
221-
let (span, use_spans, original_path, kind, has_complex_bindings): (
222-
Span,
223-
Option<UseSpans<'tcx>>,
224-
Place<'tcx>,
225-
&IllegalMoveOriginKind<'_>,
226-
bool,
227-
) = match error {
228-
GroupedMoveError::MovesFromPlace {
229-
span,
230-
original_path,
231-
ref kind,
232-
ref binds_to,
233-
..
221+
let (span, use_spans, original_path, kind) = match error {
222+
GroupedMoveError::MovesFromPlace { span, original_path, ref kind, .. }
223+
| GroupedMoveError::MovesFromValue { span, original_path, ref kind, .. } => {
224+
(span, None, original_path, kind)
234225
}
235-
| GroupedMoveError::MovesFromValue {
236-
span,
237-
original_path,
238-
ref kind,
239-
ref binds_to,
240-
..
241-
} => (span, None, original_path, kind, !binds_to.is_empty()),
242226
GroupedMoveError::OtherIllegalMove { use_spans, original_path, ref kind } => {
243-
(use_spans.args_or_use(), Some(use_spans), original_path, kind, false)
227+
(use_spans.args_or_use(), Some(use_spans), original_path, kind)
244228
}
245229
};
246230
debug!(
@@ -259,7 +243,6 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
259243
target_place,
260244
span,
261245
use_spans,
262-
has_complex_bindings,
263246
),
264247
&IllegalMoveOriginKind::InteriorOfTypeWithDestructor { container_ty: ty } => {
265248
self.cannot_move_out_of_interior_of_drop(span, ty)
@@ -302,7 +285,6 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
302285
deref_target_place: Place<'tcx>,
303286
span: Span,
304287
use_spans: Option<UseSpans<'tcx>>,
305-
has_complex_bindings: bool,
306288
) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
307289
// Inspect the type of the content behind the
308290
// borrow to provide feedback about why this
@@ -399,28 +381,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
399381
}
400382
}
401383
};
402-
let ty = move_place.ty(self.body, self.infcx.tcx).ty;
403-
let def_id = match *ty.kind() {
404-
ty::Adt(self_def, _) => self_def.did(),
405-
ty::Foreign(def_id)
406-
| ty::FnDef(def_id, _)
407-
| ty::Closure(def_id, _)
408-
| ty::Generator(def_id, ..)
409-
| ty::Opaque(def_id, _) => def_id,
410-
_ => return err,
411-
};
412-
let diag_name = self.infcx.tcx.get_diagnostic_name(def_id);
413-
if matches!(diag_name, Some(sym::Option | sym::Result))
414-
&& use_spans.map_or(true, |v| !v.for_closure())
415-
&& !has_complex_bindings
416-
{
417-
err.span_suggestion_verbose(
418-
span.shrink_to_hi(),
419-
&format!("consider borrowing the `{}`'s content", diag_name.unwrap()),
420-
".as_ref()",
421-
Applicability::MaybeIncorrect,
422-
);
423-
} else if let Some(use_spans) = use_spans {
384+
if let Some(use_spans) = use_spans {
424385
self.explain_captures(
425386
&mut err, span, span, use_spans, move_place, None, "", "", "", false, true,
426387
);

‎compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

Lines changed: 30 additions & 25 deletions
Original file line numberDiff line numberDiff line change
@@ -434,16 +434,16 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
434434

435435
match self.local_names[local] {
436436
Some(name) if !local_decl.from_compiler_desugaring() => {
437-
let label = match local_decl.local_info.as_ref().unwrap() {
438-
box LocalInfo::User(ClearCrossCrate::Set(
437+
let label = match local_decl.local_info.as_deref().unwrap() {
438+
LocalInfo::User(ClearCrossCrate::Set(
439439
mir::BindingForm::ImplicitSelf(_),
440440
)) => {
441441
let (span, suggestion) =
442442
suggest_ampmut_self(self.infcx.tcx, local_decl);
443443
Some((true, span, suggestion))
444444
}
445445

446-
box LocalInfo::User(ClearCrossCrate::Set(mir::BindingForm::Var(
446+
LocalInfo::User(ClearCrossCrate::Set(mir::BindingForm::Var(
447447
mir::VarBindingForm {
448448
binding_mode: ty::BindingMode::BindByValue(_),
449449
opt_ty_info,
@@ -473,20 +473,15 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
473473
// on for loops, RHS points to the iterator part
474474
Some(DesugaringKind::ForLoop) => {
475475
self.suggest_similar_mut_method_for_for_loop(&mut err);
476-
Some((
477-
false,
478-
opt_assignment_rhs_span.unwrap(),
479-
format!(
480-
"this iterator yields `{SIGIL}` {DESC}s",
481-
SIGIL = pointer_sigil,
482-
DESC = pointer_desc
483-
),
484-
))
476+
err.span_label(opt_assignment_rhs_span.unwrap(), format!(
477+
"this iterator yields `{pointer_sigil}` {pointer_desc}s",
478+
));
479+
None
485480
}
486481
// don't create labels for compiler-generated spans
487482
Some(_) => None,
488483
None => {
489-
let (span, suggestion) = if name != kw::SelfLower {
484+
let label = if name != kw::SelfLower {
490485
suggest_ampmut(
491486
self.infcx.tcx,
492487
local_decl,
@@ -501,7 +496,11 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
501496
..
502497
}),
503498
))) => {
504-
suggest_ampmut_self(self.infcx.tcx, local_decl)
499+
let (span, sugg) = suggest_ampmut_self(
500+
self.infcx.tcx,
501+
local_decl,
502+
);
503+
(true, span, sugg)
505504
}
506505
// explicit self (eg `self: &'a Self`)
507506
_ => suggest_ampmut(
@@ -512,12 +511,12 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
512511
),
513512
}
514513
};
515-
Some((true, span, suggestion))
514+
Some(label)
516515
}
517516
}
518517
}
519518

520-
box LocalInfo::User(ClearCrossCrate::Set(mir::BindingForm::Var(
519+
LocalInfo::User(ClearCrossCrate::Set(mir::BindingForm::Var(
521520
mir::VarBindingForm {
522521
binding_mode: ty::BindingMode::BindByReference(_),
523522
..
@@ -528,7 +527,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
528527
.map(|replacement| (true, pattern_span, replacement))
529528
}
530529

531-
box LocalInfo::User(ClearCrossCrate::Clear) => {
530+
LocalInfo::User(ClearCrossCrate::Clear) => {
532531
bug!("saw cleared local state")
533532
}
534533

@@ -559,7 +558,12 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
559558
}
560559
}
561560
Some((false, err_label_span, message)) => {
562-
err.span_label(err_label_span, &message);
561+
err.span_label(
562+
err_label_span,
563+
&format!(
564+
"consider changing this binding's type to be: `{message}`"
565+
),
566+
);
563567
}
564568
None => {}
565569
}
@@ -1004,7 +1008,7 @@ fn suggest_ampmut<'tcx>(
10041008
local_decl: &mir::LocalDecl<'tcx>,
10051009
opt_assignment_rhs_span: Option<Span>,
10061010
opt_ty_info: Option<Span>,
1007-
) -> (Span, String) {
1011+
) -> (bool, Span, String) {
10081012
if let Some(assignment_rhs_span) = opt_assignment_rhs_span
10091013
&& let Ok(src) = tcx.sess.source_map().span_to_snippet(assignment_rhs_span)
10101014
{
@@ -1028,37 +1032,38 @@ fn suggest_ampmut<'tcx>(
10281032
let lt_name = &src[1..ws_pos];
10291033
let ty = src[ws_pos..].trim_start();
10301034
if !is_mutbl(ty) {
1031-
return (assignment_rhs_span, format!("&{lt_name} mut {ty}"));
1035+
return (true, assignment_rhs_span, format!("&{lt_name} mut {ty}"));
10321036
}
10331037
} else if let Some(stripped) = src.strip_prefix('&') {
10341038
let stripped = stripped.trim_start();
10351039
if !is_mutbl(stripped) {
1036-
return (assignment_rhs_span, format!("&mut {stripped}"));
1040+
return (true, assignment_rhs_span, format!("&mut {stripped}"));
10371041
}
10381042
}
10391043
}
10401044

1041-
let highlight_span = match opt_ty_info {
1045+
let (suggestability, highlight_span) = match opt_ty_info {
10421046
// if this is a variable binding with an explicit type,
10431047
// try to highlight that for the suggestion.
1044-
Some(ty_span) => ty_span,
1048+
Some(ty_span) => (true, ty_span),
10451049

10461050
// otherwise, just highlight the span associated with
10471051
// the (MIR) LocalDecl.
1048-
None => local_decl.source_info.span,
1052+
None => (false, local_decl.source_info.span),
10491053
};
10501054

10511055
if let Ok(src) = tcx.sess.source_map().span_to_snippet(highlight_span)
10521056
&& let (true, Some(ws_pos)) = (src.starts_with("&'"), src.find(char::is_whitespace))
10531057
{
10541058
let lt_name = &src[1..ws_pos];
10551059
let ty = &src[ws_pos..];
1056-
return (highlight_span, format!("&{} mut{}", lt_name, ty));
1060+
return (true, highlight_span, format!("&{} mut{}", lt_name, ty));
10571061
}
10581062

10591063
let ty_mut = local_decl.ty.builtin_deref(true).unwrap();
10601064
assert_eq!(ty_mut.mutbl, hir::Mutability::Not);
10611065
(
1066+
suggestability,
10621067
highlight_span,
10631068
if local_decl.ty.is_region_ptr() {
10641069
format!("&mut {}", ty_mut.ty)

‎compiler/rustc_mir_build/src/build/mod.rs

Lines changed: 5 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -162,7 +162,11 @@ fn mir_build(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> Body<'_
162162
let opt_ty_info;
163163
let self_arg;
164164
if let Some(ref fn_decl) = tcx.hir().fn_decl_by_hir_id(owner_id) {
165-
opt_ty_info = fn_decl.inputs.get(index).map(|ty| ty.span);
165+
opt_ty_info = fn_decl
166+
.inputs
167+
.get(index)
168+
// Make sure that inferred closure args have no type span
169+
.and_then(|ty| if arg.pat.span != ty.span { Some(ty.span) } else { None });
166170
self_arg = if index == 0 && fn_decl.implicit_self.has_implicit_self() {
167171
match fn_decl.implicit_self {
168172
hir::ImplicitSelfKind::Imm => Some(ImplicitSelfKind::Imm),

‎src/test/ui/binop/binop-move-semantics.stderr

Lines changed: 14 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -63,8 +63,20 @@ LL | use_mut(n); use_imm(m);
6363
error[E0507]: cannot move out of `*m` which is behind a mutable reference
6464
--> $DIR/binop-move-semantics.rs:30:5
6565
|
66-
LL | *m
67-
| ^^ move occurs because `*m` has type `T`, which does not implement the `Copy` trait
66+
LL | *m
67+
| -^
68+
| |
69+
| _____move occurs because `*m` has type `T`, which does not implement the `Copy` trait
70+
| |
71+
LL | | +
72+
LL | | *n;
73+
| |______- `*m` moved due to usage in operator
74+
|
75+
note: calling this operator moves the left-hand side
76+
--> $SRC_DIR/core/src/ops/arith.rs:LL:COL
77+
|
78+
LL | fn add(self, rhs: Rhs) -> Self::Output;
79+
| ^^^^
6880

6981
error[E0507]: cannot move out of `*n` which is behind a shared reference
7082
--> $DIR/binop-move-semantics.rs:32:5

‎src/test/ui/borrowck/borrowck-borrow-mut-base-ptr-in-aliasable-loc.stderr

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@ error[E0594]: cannot assign to `**t1`, which is behind a `&` reference
22
--> $DIR/borrowck-borrow-mut-base-ptr-in-aliasable-loc.rs:9:5
33
|
44
LL | let t1 = t0;
5-
| -- help: consider changing this to be a mutable reference: `&mut &mut isize`
5+
| -- consider changing this binding's type to be: `&mut &mut isize`
66
LL | let p: &isize = &**t0;
77
LL | **t1 = 22;
88
| ^^^^^^^^^ `t1` is a `&` reference, so the data it refers to cannot be written

‎src/test/ui/borrowck/issue-85765.rs

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1,7 +1,7 @@
11
fn main() {
22
let mut test = Vec::new();
33
let rofl: &Vec<Vec<i32>> = &mut test;
4-
//~^ HELP consider changing this to be a mutable reference
4+
//~^ NOTE consider changing this binding's type to be
55
rofl.push(Vec::new());
66
//~^ ERROR cannot borrow `*rofl` as mutable, as it is behind a `&` reference
77
//~| NOTE `rofl` is a `&` reference, so the data it refers to cannot be borrowed as mutable
@@ -15,14 +15,14 @@ fn main() {
1515

1616
#[rustfmt::skip]
1717
let x: &usize = &mut{0};
18-
//~^ HELP consider changing this to be a mutable reference
18+
//~^ NOTE consider changing this binding's type to be
1919
*x = 1;
2020
//~^ ERROR cannot assign to `*x`, which is behind a `&` reference
2121
//~| NOTE `x` is a `&` reference, so the data it refers to cannot be written
2222

2323
#[rustfmt::skip]
2424
let y: &usize = &mut(0);
25-
//~^ HELP consider changing this to be a mutable reference
25+
//~^ NOTE consider changing this binding's type to be
2626
*y = 1;
2727
//~^ ERROR cannot assign to `*y`, which is behind a `&` reference
2828
//~| NOTE `y` is a `&` reference, so the data it refers to cannot be written

‎src/test/ui/borrowck/issue-85765.stderr

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@ error[E0596]: cannot borrow `*rofl` as mutable, as it is behind a `&` reference
22
--> $DIR/issue-85765.rs:5:5
33
|
44
LL | let rofl: &Vec<Vec<i32>> = &mut test;
5-
| ---- help: consider changing this to be a mutable reference: `&mut Vec<Vec<i32>>`
5+
| ---- consider changing this binding's type to be: `&mut Vec<Vec<i32>>`
66
LL |
77
LL | rofl.push(Vec::new());
88
| ^^^^^^^^^^^^^^^^^^^^^ `rofl` is a `&` reference, so the data it refers to cannot be borrowed as mutable
@@ -20,7 +20,7 @@ error[E0594]: cannot assign to `*x`, which is behind a `&` reference
2020
--> $DIR/issue-85765.rs:19:5
2121
|
2222
LL | let x: &usize = &mut{0};
23-
| - help: consider changing this to be a mutable reference: `&mut usize`
23+
| - consider changing this binding's type to be: `&mut usize`
2424
LL |
2525
LL | *x = 1;
2626
| ^^^^^^ `x` is a `&` reference, so the data it refers to cannot be written
@@ -29,7 +29,7 @@ error[E0594]: cannot assign to `*y`, which is behind a `&` reference
2929
--> $DIR/issue-85765.rs:26:5
3030
|
3131
LL | let y: &usize = &mut(0);
32-
| - help: consider changing this to be a mutable reference: `&mut usize`
32+
| - consider changing this binding's type to be: `&mut usize`
3333
LL |
3434
LL | *y = 1;
3535
| ^^^^^^ `y` is a `&` reference, so the data it refers to cannot be written

‎src/test/ui/borrowck/issue-91206.rs

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,8 @@ impl TestClient {
99
fn main() {
1010
let client = TestClient;
1111
let inner = client.get_inner_ref();
12-
//~^ HELP consider changing this to be a mutable reference
12+
//~^ NOTE consider changing this binding's type to be
1313
inner.clear();
1414
//~^ ERROR cannot borrow `*inner` as mutable, as it is behind a `&` reference [E0596]
15+
//~| NOTE `inner` is a `&` reference, so the data it refers to cannot be borrowed as mutable
1516
}

‎src/test/ui/borrowck/issue-91206.stderr

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@ error[E0596]: cannot borrow `*inner` as mutable, as it is behind a `&` reference
22
--> $DIR/issue-91206.rs:13:5
33
|
44
LL | let inner = client.get_inner_ref();
5-
| ----- help: consider changing this to be a mutable reference: `&mut Vec<usize>`
5+
| ----- consider changing this binding's type to be: `&mut Vec<usize>`
66
LL |
77
LL | inner.clear();
88
| ^^^^^^^^^^^^^ `inner` is a `&` reference, so the data it refers to cannot be borrowed as mutable

‎src/test/ui/borrowck/issue-92015.stderr

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@ error[E0594]: cannot assign to `*foo`, which is behind a `&` reference
22
--> $DIR/issue-92015.rs:6:5
33
|
44
LL | let foo = Some(&0).unwrap();
5-
| --- help: consider changing this to be a mutable reference: `&mut i32`
5+
| --- consider changing this binding's type to be: `&mut i32`
66
LL | *foo = 1;
77
| ^^^^^^^^ `foo` is a `&` reference, so the data it refers to cannot be written
88

‎src/test/ui/borrowck/suggest-as-ref-on-mut-closure.rs

Lines changed: 16 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,16 @@
1+
// This is not exactly right, yet.
2+
3+
// Ideally we should be suggesting `as_mut` for the first case,
4+
// and suggesting to change `as_ref` to `as_mut` in the second.
5+
6+
fn x(cb: &mut Option<&mut dyn FnMut()>) {
7+
cb.map(|cb| cb());
8+
//~^ ERROR cannot move out of `*cb` which is behind a mutable reference
9+
}
10+
11+
fn x2(cb: &mut Option<&mut dyn FnMut()>) {
12+
cb.as_ref().map(|cb| cb());
13+
//~^ ERROR cannot borrow `*cb` as mutable, as it is behind a `&` reference
14+
}
15+
16+
fn main() {}

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