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Rollup merge of #106360 - estebank:remove-borrow-suggestion, r=compiler-errors

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Tweak E0277 `&`-removal suggestions

Fix #64068, fix #84837.
This commit is contained in:
Michael Goulet 2023-01-11 22:25:49 -08:00 committed by GitHub
commit 54f6fea818
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GPG Key ID: 4AEE18F83AFDEB23
17 changed files with 253 additions and 76 deletions
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136
compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
View File

@ -1361,57 +1361,117 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
err: &mut Diagnostic,
trait_pred: ty::PolyTraitPredicate<'tcx>,
) -> bool {
let span = obligation.cause.span;
let mut span = obligation.cause.span;
let mut trait_pred = trait_pred;
let mut code = obligation.cause.code();
while let Some((c, Some(parent_trait_pred))) = code.parent() {
// We want the root obligation, in order to detect properly handle
// `for _ in &mut &mut vec![] {}`.
code = c;
trait_pred = parent_trait_pred;
}
while span.desugaring_kind().is_some() {
// Remove all the hir desugaring contexts while maintaining the macro contexts.
span.remove_mark();
}
let mut expr_finder = super::FindExprBySpan::new(span);
let Some(hir::Node::Expr(body)) = self.tcx.hir().find(obligation.cause.body_id) else {
return false;
};
expr_finder.visit_expr(&body);
let mut maybe_suggest = |suggested_ty, count, suggestions| {
// Remapping bound vars here
let trait_pred_and_suggested_ty =
trait_pred.map_bound(|trait_pred| (trait_pred, suggested_ty));
let mut suggested = false;
if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
let refs_number =
snippet.chars().filter(|c| !c.is_whitespace()).take_while(|c| *c == '&').count();
if let Some('\'') = snippet.chars().filter(|c| !c.is_whitespace()).nth(refs_number) {
// Do not suggest removal of borrow from type arguments.
return false;
let new_obligation = self.mk_trait_obligation_with_new_self_ty(
obligation.param_env,
trait_pred_and_suggested_ty,
);
if self.predicate_may_hold(&new_obligation) {
let msg = if count == 1 {
"consider removing the leading `&`-reference".to_string()
} else {
format!("consider removing {count} leading `&`-references")
};
err.multipart_suggestion_verbose(
&msg,
suggestions,
Applicability::MachineApplicable,
);
true
} else {
false
}
};
// Skipping binder here, remapping below
let mut suggested_ty = trait_pred.self_ty().skip_binder();
// Maybe suggest removal of borrows from types in type parameters, like in
// `src/test/ui/not-panic/not-panic-safe.rs`.
let mut count = 0;
let mut suggestions = vec![];
// Skipping binder here, remapping below
let mut suggested_ty = trait_pred.self_ty().skip_binder();
if let Some(mut hir_ty) = expr_finder.ty_result {
while let hir::TyKind::Ref(_, mut_ty) = &hir_ty.kind {
count += 1;
let span = hir_ty.span.until(mut_ty.ty.span);
suggestions.push((span, String::new()));
for refs_remaining in 0..refs_number {
let ty::Ref(_, inner_ty, _) = suggested_ty.kind() else {
break;
};
suggested_ty = *inner_ty;
// Remapping bound vars here
let trait_pred_and_suggested_ty =
trait_pred.map_bound(|trait_pred| (trait_pred, suggested_ty));
hir_ty = mut_ty.ty;
let new_obligation = self.mk_trait_obligation_with_new_self_ty(
obligation.param_env,
trait_pred_and_suggested_ty,
);
if self.predicate_may_hold(&new_obligation) {
let sp = self
.tcx
.sess
.source_map()
.span_take_while(span, |c| c.is_whitespace() || *c == '&');
let remove_refs = refs_remaining + 1;
let msg = if remove_refs == 1 {
"consider removing the leading `&`-reference".to_string()
} else {
format!("consider removing {} leading `&`-references", remove_refs)
};
err.span_suggestion_short(sp, &msg, "", Applicability::MachineApplicable);
suggested = true;
break;
if maybe_suggest(suggested_ty, count, suggestions.clone()) {
return true;
}
}
}
suggested
// Maybe suggest removal of borrows from expressions, like in `for i in &&&foo {}`.
let Some(mut expr) = expr_finder.result else { return false; };
let mut count = 0;
let mut suggestions = vec![];
// Skipping binder here, remapping below
let mut suggested_ty = trait_pred.self_ty().skip_binder();
'outer: loop {
while let hir::ExprKind::AddrOf(_, _, borrowed) = expr.kind {
count += 1;
let span = if expr.span.eq_ctxt(borrowed.span) {
expr.span.until(borrowed.span)
} else {
expr.span.with_hi(expr.span.lo() + BytePos(1))
};
suggestions.push((span, String::new()));
let ty::Ref(_, inner_ty, _) = suggested_ty.kind() else {
break 'outer;
};
suggested_ty = *inner_ty;
expr = borrowed;
if maybe_suggest(suggested_ty, count, suggestions.clone()) {
return true;
}
}
if let hir::ExprKind::Path(hir::QPath::Resolved(None, path)) = expr.kind
&& let hir::def::Res::Local(hir_id) = path.res
&& let Some(hir::Node::Pat(binding)) = self.tcx.hir().find(hir_id)
&& let Some(hir::Node::Local(local)) = self.tcx.hir().find_parent(binding.hir_id)
&& let None = local.ty
&& let Some(binding_expr) = local.init
{
expr = binding_expr;
} else {
break 'outer;
}
}
false
}
fn suggest_remove_await(&self, obligation: &PredicateObligation<'tcx>, err: &mut Diagnostic) {

6
tests/ui/auto-traits/typeck-default-trait-impl-precedence.stderr
View File

@ -4,7 +4,6 @@ error[E0277]: the trait bound `u32: Signed` is not satisfied
LL | is_defaulted::<&'static u32>();
| ^^^^^^^^^^^^ the trait `Signed` is not implemented for `u32`
|
= help: the trait `Signed` is implemented for `i32`
note: required for `&'static u32` to implement `Defaulted`
--> $DIR/typeck-default-trait-impl-precedence.rs:10:19
|
@ -17,6 +16,11 @@ note: required by a bound in `is_defaulted`
|
LL | fn is_defaulted<T:Defaulted>() { }
| ^^^^^^^^^ required by this bound in `is_defaulted`
help: consider removing the leading `&`-reference
|
LL - is_defaulted::<&'static u32>();
LL + is_defaulted::<u32>();
|
error: aborting due to previous error

12
tests/ui/impl-trait/in-trait/issue-102140.stderr
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@ -2,11 +2,15 @@ error[E0277]: the trait bound `&dyn MyTrait: MyTrait` is not satisfied
--> $DIR/issue-102140.rs:23:22
|
LL | MyTrait::foo(&self)
| ------------ -^^^^
| | |
| | the trait `MyTrait` is not implemented for `&dyn MyTrait`
| | help: consider removing the leading `&`-reference
| ------------ ^^^^^ the trait `MyTrait` is not implemented for `&dyn MyTrait`
| |
| required by a bound introduced by this call
|
help: consider removing the leading `&`-reference
|
LL - MyTrait::foo(&self)
LL + MyTrait::foo(self)
|
error[E0277]: the trait bound `&dyn MyTrait: MyTrait` is not satisfied
--> $DIR/issue-102140.rs:23:9

12
tests/ui/kindck/kindck-copy.stderr
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@ -4,12 +4,16 @@ error[E0277]: the trait bound `&'static mut isize: Copy` is not satisfied
LL | assert_copy::<&'static mut isize>();
| ^^^^^^^^^^^^^^^^^^ the trait `Copy` is not implemented for `&'static mut isize`
|
= help: the trait `Copy` is implemented for `isize`
note: required by a bound in `assert_copy`
--> $DIR/kindck-copy.rs:5:18
|
LL | fn assert_copy<T:Copy>() { }
| ^^^^ required by this bound in `assert_copy`
help: consider removing the leading `&`-reference
|
LL - assert_copy::<&'static mut isize>();
LL + assert_copy::<isize>();
|
error[E0277]: the trait bound `&'a mut isize: Copy` is not satisfied
--> $DIR/kindck-copy.rs:28:19
@ -17,12 +21,16 @@ error[E0277]: the trait bound `&'a mut isize: Copy` is not satisfied
LL | assert_copy::<&'a mut isize>();
| ^^^^^^^^^^^^^ the trait `Copy` is not implemented for `&'a mut isize`
|
= help: the trait `Copy` is implemented for `isize`
note: required by a bound in `assert_copy`
--> $DIR/kindck-copy.rs:5:18
|
LL | fn assert_copy<T:Copy>() { }
| ^^^^ required by this bound in `assert_copy`
help: consider removing the leading `&`-reference
|
LL - assert_copy::<&'a mut isize>();
LL + assert_copy::<isize>();
|
error[E0277]: the trait bound `Box<isize>: Copy` is not satisfied
--> $DIR/kindck-copy.rs:31:19

10
tests/ui/not-panic/not-panic-safe-4.stderr
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@ -12,6 +12,11 @@ note: required by a bound in `assert`
|
LL | fn assert<T: UnwindSafe + ?Sized>() {}
| ^^^^^^^^^^ required by this bound in `assert`
help: consider removing the leading `&`-reference
|
LL - assert::<&RefCell<i32>>();
LL + assert::<RefCell<i32>>();
|
error[E0277]: the type `UnsafeCell<isize>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
--> $DIR/not-panic-safe-4.rs:9:14
@ -28,6 +33,11 @@ note: required by a bound in `assert`
|
LL | fn assert<T: UnwindSafe + ?Sized>() {}
| ^^^^^^^^^^ required by this bound in `assert`
help: consider removing the leading `&`-reference
|
LL - assert::<&RefCell<i32>>();
LL + assert::<RefCell<i32>>();
|
error: aborting due to 2 previous errors

4
tests/ui/not-panic/not-panic-safe.rs
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@ -5,6 +5,6 @@ use std::panic::UnwindSafe;
fn assert<T: UnwindSafe + ?Sized>() {}
fn main() {
assert::<&mut i32>();
//~^ ERROR the type `&mut i32` may not be safely transferred across an unwind boundary
assert::<&mut &mut &i32>();
//~^ ERROR the type `&mut &mut &i32` may not be safely transferred across an unwind boundary
}

18
tests/ui/not-panic/not-panic-safe.stderr
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@ -1,19 +1,21 @@
error[E0277]: the type `&mut i32` may not be safely transferred across an unwind boundary
error[E0277]: the type `&mut &mut &i32` may not be safely transferred across an unwind boundary
--> $DIR/not-panic-safe.rs:8:14
|
LL | assert::<&mut i32>();
| -^^^^^^^
| |
| `&mut i32` may not be safely transferred across an unwind boundary
| help: consider removing the leading `&`-reference
LL | assert::<&mut &mut &i32>();
| ^^^^^^^^^^^^^^ `&mut &mut &i32` may not be safely transferred across an unwind boundary
|
= help: the trait `UnwindSafe` is not implemented for `&mut i32`
= note: `UnwindSafe` is implemented for `&i32`, but not for `&mut i32`
= help: the trait `UnwindSafe` is not implemented for `&mut &mut &i32`
= note: `UnwindSafe` is implemented for `&&mut &i32`, but not for `&mut &mut &i32`
note: required by a bound in `assert`
--> $DIR/not-panic-safe.rs:5:14
|
LL | fn assert<T: UnwindSafe + ?Sized>() {}
| ^^^^^^^^^^ required by this bound in `assert`
help: consider removing 2 leading `&`-references
|
LL - assert::<&mut &mut &i32>();
LL + assert::<&i32>();
|
error: aborting due to previous error

10
tests/ui/suggestions/suggest-remove-refs-1.stderr
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@ -2,13 +2,15 @@ error[E0277]: `&Enumerate<std::slice::Iter<'_, {integer}>>` is not an iterator
--> $DIR/suggest-remove-refs-1.rs:6:19
|
LL | for (i, _) in &v.iter().enumerate() {
| -^^^^^^^^^^^^^^^^^^^^
| |
| `&Enumerate<std::slice::Iter<'_, {integer}>>` is not an iterator
| help: consider removing the leading `&`-reference
| ^^^^^^^^^^^^^^^^^^^^^ `&Enumerate<std::slice::Iter<'_, {integer}>>` is not an iterator
|
= help: the trait `Iterator` is not implemented for `&Enumerate<std::slice::Iter<'_, {integer}>>`
= note: required for `&Enumerate<std::slice::Iter<'_, {integer}>>` to implement `IntoIterator`
help: consider removing the leading `&`-reference
|
LL - for (i, _) in &v.iter().enumerate() {
LL + for (i, _) in v.iter().enumerate() {
|
error: aborting due to previous error

10
tests/ui/suggestions/suggest-remove-refs-2.stderr
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@ -2,13 +2,15 @@ error[E0277]: `&&&&&Enumerate<std::slice::Iter<'_, {integer}>>` is not an iterat
--> $DIR/suggest-remove-refs-2.rs:6:19
|
LL | for (i, _) in & & & & &v.iter().enumerate() {
| ---------^^^^^^^^^^^^^^^^^^^^
| |
| `&&&&&Enumerate<std::slice::Iter<'_, {integer}>>` is not an iterator
| help: consider removing 5 leading `&`-references
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `&&&&&Enumerate<std::slice::Iter<'_, {integer}>>` is not an iterator
|
= help: the trait `Iterator` is not implemented for `&&&&&Enumerate<std::slice::Iter<'_, {integer}>>`
= note: required for `&&&&&Enumerate<std::slice::Iter<'_, {integer}>>` to implement `IntoIterator`
help: consider removing 5 leading `&`-references
|
LL - for (i, _) in & & & & &v.iter().enumerate() {
LL + for (i, _) in v.iter().enumerate() {
|
error: aborting due to previous error

20
tests/ui/suggestions/suggest-remove-refs-3.stderr
View File

@ -1,18 +1,20 @@
error[E0277]: `&&&&&Enumerate<std::slice::Iter<'_, {integer}>>` is not an iterator
--> $DIR/suggest-remove-refs-3.rs:6:19
|
LL | for (i, _) in & & &
| ____________________^
| | ___________________|
| ||
LL | || & &v
| ||___________- help: consider removing 5 leading `&`-references
LL | | .iter()
LL | | .enumerate() {
| |_____________________^ `&&&&&Enumerate<std::slice::Iter<'_, {integer}>>` is not an iterator
LL | for (i, _) in & & &
| ___________________^
LL | | & &v
LL | | .iter()
LL | | .enumerate() {
| |____________________^ `&&&&&Enumerate<std::slice::Iter<'_, {integer}>>` is not an iterator
|
= help: the trait `Iterator` is not implemented for `&&&&&Enumerate<std::slice::Iter<'_, {integer}>>`
= note: required for `&&&&&Enumerate<std::slice::Iter<'_, {integer}>>` to implement `IntoIterator`
help: consider removing 5 leading `&`-references
|
LL - for (i, _) in & & &
LL + for (i, _) in v
|
error: aborting due to previous error

5
tests/ui/suggestions/suggest-remove-refs-4.fixed Normal file
View File

@ -0,0 +1,5 @@
// run-rustfix
fn main() {
let foo = [1,2,3].iter();
for _i in foo {} //~ ERROR E0277
}

5
tests/ui/suggestions/suggest-remove-refs-4.rs Normal file
View File

@ -0,0 +1,5 @@
// run-rustfix
fn main() {
let foo = &[1,2,3].iter();
for _i in &foo {} //~ ERROR E0277
}

17
tests/ui/suggestions/suggest-remove-refs-4.stderr Normal file
View File

@ -0,0 +1,17 @@
error[E0277]: `&&std::slice::Iter<'_, {integer}>` is not an iterator
--> $DIR/suggest-remove-refs-4.rs:4:15
|
LL | for _i in &foo {}
| ^^^^ `&&std::slice::Iter<'_, {integer}>` is not an iterator
|
= help: the trait `Iterator` is not implemented for `&&std::slice::Iter<'_, {integer}>`
= note: required for `&&std::slice::Iter<'_, {integer}>` to implement `IntoIterator`
help: consider removing 2 leading `&`-references
|
LL ~ let foo = [1,2,3].iter();
LL ~ for _i in foo {}
|
error: aborting due to previous error
For more information about this error, try `rustc --explain E0277`.

8
tests/ui/suggestions/suggest-remove-refs-5.fixed Normal file
View File

@ -0,0 +1,8 @@
// run-rustfix
fn main() {
let v = &mut Vec::<i32>::new();
for _ in v {} //~ ERROR E0277
let v = &mut [1u8];
for _ in v {} //~ ERROR E0277
}

8
tests/ui/suggestions/suggest-remove-refs-5.rs Normal file
View File

@ -0,0 +1,8 @@
// run-rustfix
fn main() {
let v = &mut &mut Vec::<i32>::new();
for _ in &mut &mut v {} //~ ERROR E0277
let v = &mut &mut [1u8];
for _ in &mut v {} //~ ERROR E0277
}

37
tests/ui/suggestions/suggest-remove-refs-5.stderr Normal file
View File

@ -0,0 +1,37 @@
error[E0277]: `Vec<i32>` is not an iterator
--> $DIR/suggest-remove-refs-5.rs:4:14
|
LL | for _ in &mut &mut v {}
| ^^^^^^^^^^^ `Vec<i32>` is not an iterator; try calling `.into_iter()` or `.iter()`
|
= help: the trait `Iterator` is not implemented for `Vec<i32>`
= note: required for `&mut Vec<i32>` to implement `Iterator`
= note: 3 redundant requirements hidden
= note: required for `&mut &mut &mut &mut Vec<i32>` to implement `Iterator`
= note: required for `&mut &mut &mut &mut Vec<i32>` to implement `IntoIterator`
help: consider removing 3 leading `&`-references
|
LL ~ let v = &mut Vec::<i32>::new();
LL ~ for _ in v {}
|
error[E0277]: `[u8; 1]` is not an iterator
--> $DIR/suggest-remove-refs-5.rs:7:14
|
LL | for _ in &mut v {}
| ^^^^^^ `[u8; 1]` is not an iterator; try calling `.into_iter()` or `.iter()`
|
= help: the trait `Iterator` is not implemented for `[u8; 1]`
= note: required for `&mut [u8; 1]` to implement `Iterator`
= note: 2 redundant requirements hidden
= note: required for `&mut &mut &mut [u8; 1]` to implement `Iterator`
= note: required for `&mut &mut &mut [u8; 1]` to implement `IntoIterator`
help: consider removing 2 leading `&`-references
|
LL ~ let v = &mut [1u8];
LL ~ for _ in v {}
|
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0277`.

11
tests/ui/typeck/issue-57404.stderr
View File

@ -2,14 +2,17 @@ error[E0277]: `&mut ()` is not a tuple
--> $DIR/issue-57404.rs:6:41
|
LL | handlers.unwrap().as_mut().call_mut(&mut ());
| -------- -^^^^^^
| | |
| | the trait `Tuple` is not implemented for `&mut ()`
| | help: consider removing the leading `&`-reference
| -------- ^^^^^^^ the trait `Tuple` is not implemented for `&mut ()`
| |
| required by a bound introduced by this call
|
note: required by a bound in `call_mut`
--> $SRC_DIR/core/src/ops/function.rs:LL:COL
help: consider removing the leading `&`-reference
|
LL - handlers.unwrap().as_mut().call_mut(&mut ());
LL + handlers.unwrap().as_mut().call_mut(());
|
error: aborting due to previous error