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Rollup merge of #83251 - estebank:issue-83241, r=oli-obk

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Suggestion for call on immutable binding of mutable type

When calling a method requiring a mutable self borrow on an inmutable
to a mutable borrow of the type, suggest making the binding mutable.

Fix #83241.
This commit is contained in:
Guillaume Gomez 2021-08-29 16:25:26 +02:00 committed by GitHub
commit 22973a8844
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GPG Key ID: 4AEE18F83AFDEB23
6 changed files with 210 additions and 38 deletions
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80
compiler/rustc_mir/src/borrow_check/diagnostics/mutability_errors.rs
View File

@ -5,11 +5,14 @@ use rustc_middle::mir::{Mutability, Place, PlaceRef, ProjectionElem};
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_middle::{
hir::place::PlaceBase,
mir::{self, ClearCrossCrate, Local, LocalDecl, LocalInfo, LocalKind, Location},
mir::{
self, BindingForm, ClearCrossCrate, ImplicitSelfKind, Local, LocalDecl, LocalInfo,
LocalKind, Location,
},
};
use rustc_span::source_map::DesugaringKind;
use rustc_span::symbol::{kw, Symbol};
use rustc_span::Span;
use rustc_span::{BytePos, Span};
use crate::borrow_check::diagnostics::BorrowedContentSource;
use crate::borrow_check::MirBorrowckCtxt;
@ -241,13 +244,74 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
.map(|l| mut_borrow_of_mutable_ref(l, self.local_names[local]))
.unwrap_or(false) =>
{
let decl = &self.body.local_decls[local];
err.span_label(span, format!("cannot {ACT}", ACT = act));
err.span_suggestion(
span,
"try removing `&mut` here",
String::new(),
Applicability::MaybeIncorrect,
);
if let Some(mir::Statement {
source_info,
kind:
mir::StatementKind::Assign(box (
_,
mir::Rvalue::Ref(
_,
mir::BorrowKind::Mut { allow_two_phase_borrow: false },
_,
),
)),
..
}) = &self.body[location.block].statements.get(location.statement_index)
{
match decl.local_info {
Some(box LocalInfo::User(ClearCrossCrate::Set(BindingForm::Var(
mir::VarBindingForm {
binding_mode: ty::BindingMode::BindByValue(Mutability::Not),
opt_ty_info: Some(sp),
opt_match_place: _,
pat_span: _,
},
)))) => {
err.span_note(sp, "the binding is already a mutable borrow");
}
_ => {
err.span_note(
decl.source_info.span,
"the binding is already a mutable borrow",
);
}
}
if let Ok(snippet) =
self.infcx.tcx.sess.source_map().span_to_snippet(source_info.span)
{
if snippet.starts_with("&mut ") {
// We don't have access to the HIR to get accurate spans, but we can
// give a best effort structured suggestion.
err.span_suggestion_verbose(
source_info.span.with_hi(source_info.span.lo() + BytePos(5)),
"try removing `&mut` here",
String::new(),
Applicability::MachineApplicable,
);
} else {
// This can occur with things like `(&mut self).foo()`.
err.span_help(source_info.span, "try removing `&mut` here");
}
} else {
err.span_help(source_info.span, "try removing `&mut` here");
}
} else if decl.mutability == Mutability::Not
&& !matches!(
decl.local_info,
Some(box LocalInfo::User(ClearCrossCrate::Set(BindingForm::ImplicitSelf(
ImplicitSelfKind::MutRef
))))
)
{
err.span_suggestion_verbose(
decl.source_info.span.shrink_to_lo(),
"consider making the binding mutable",
"mut ".to_string(),
Applicability::MachineApplicable,
);
}
}
// We want to suggest users use `let mut` for local (user

28
src/test/ui/borrowck/mut-borrow-of-mut-ref.rs
View File

@ -2,12 +2,36 @@
#![crate_type = "rlib"]
pub fn f(b: &mut i32) {
g(&mut b);
//~^ NOTE the binding is already a mutable borrow
//~| NOTE the binding is already a mutable borrow
h(&mut b);
//~^ ERROR cannot borrow
//~| NOTE cannot borrow as mutable
//~| HELP try removing `&mut` here
g(&mut &mut b);
//~^ ERROR cannot borrow
//~| NOTE cannot borrow as mutable
//~| HELP try removing `&mut` here
}
pub fn g(_: &mut i32) {}
pub fn g(b: &mut i32) { //~ NOTE the binding is already a mutable borrow
h(&mut &mut b);
//~^ ERROR cannot borrow
//~| NOTE cannot borrow as mutable
//~| HELP try removing `&mut` here
}
pub fn h(_: &mut i32) {}
trait Foo {
fn bar(&mut self);
}
impl Foo for &mut String {
fn bar(&mut self) {}
}
pub fn baz(f: &mut String) { //~ HELP consider making the binding mutable
f.bar(); //~ ERROR cannot borrow `f` as mutable, as it is not declared as mutable
//~^ NOTE cannot borrow as mutable
}

68
src/test/ui/borrowck/mut-borrow-of-mut-ref.stderr
View File

@ -1,21 +1,65 @@
error[E0596]: cannot borrow `b` as mutable, as it is not declared as mutable
--> $DIR/mut-borrow-of-mut-ref.rs:5:7
--> $DIR/mut-borrow-of-mut-ref.rs:7:7
|
LL | g(&mut b);
| ^^^^^^
| |
| cannot borrow as mutable
| help: try removing `&mut` here
LL | h(&mut b);
| ^^^^^^ cannot borrow as mutable
|
note: the binding is already a mutable borrow
--> $DIR/mut-borrow-of-mut-ref.rs:4:13
|
LL | pub fn f(b: &mut i32) {
| ^^^^^^^^
help: try removing `&mut` here
|
LL - h(&mut b);
LL + h(b);
|
error[E0596]: cannot borrow `b` as mutable, as it is not declared as mutable
--> $DIR/mut-borrow-of-mut-ref.rs:8:12
--> $DIR/mut-borrow-of-mut-ref.rs:11:12
|
LL | g(&mut &mut b);
| ^^^^^^
| |
| cannot borrow as mutable
| help: try removing `&mut` here
| ^^^^^^ cannot borrow as mutable
|
note: the binding is already a mutable borrow
--> $DIR/mut-borrow-of-mut-ref.rs:4:13
|
LL | pub fn f(b: &mut i32) {
| ^^^^^^^^
help: try removing `&mut` here
|
LL - g(&mut &mut b);
LL + g(&mut b);
|
error: aborting due to 2 previous errors
error[E0596]: cannot borrow `b` as mutable, as it is not declared as mutable
--> $DIR/mut-borrow-of-mut-ref.rs:18:12
|
LL | h(&mut &mut b);
| ^^^^^^ cannot borrow as mutable
|
note: the binding is already a mutable borrow
--> $DIR/mut-borrow-of-mut-ref.rs:17:13
|
LL | pub fn g(b: &mut i32) {
| ^^^^^^^^
help: try removing `&mut` here
|
LL - h(&mut &mut b);
LL + h(&mut b);
|
error[E0596]: cannot borrow `f` as mutable, as it is not declared as mutable
--> $DIR/mut-borrow-of-mut-ref.rs:35:5
|
LL | f.bar();
| ^ cannot borrow as mutable
|
help: consider making the binding mutable
|
LL | pub fn baz(mut f: &mut String) {
| +++
error: aborting due to 4 previous errors
For more information about this error, try `rustc --explain E0596`.

28
src/test/ui/did_you_mean/issue-31424.stderr
View File

@ -1,11 +1,19 @@
error[E0596]: cannot borrow `self` as mutable, as it is not declared as mutable
--> $DIR/issue-31424.rs:7:9
|
LL | (&mut self).bar();
| ^^^^^^^^^^^ cannot borrow as mutable
|
note: the binding is already a mutable borrow
--> $DIR/issue-31424.rs:6:12
|
LL | fn foo(&mut self) {
| ^^^^^^^^^
help: try removing `&mut` here
--> $DIR/issue-31424.rs:7:9
|
LL | (&mut self).bar();
| ^^^^^^^^^^^
| |
| cannot borrow as mutable
| help: try removing `&mut` here
warning: function cannot return without recursing
--> $DIR/issue-31424.rs:13:5
@ -22,11 +30,19 @@ LL | (&mut self).bar();
error[E0596]: cannot borrow `self` as mutable, as it is not declared as mutable
--> $DIR/issue-31424.rs:16:9
|
LL | (&mut self).bar();
| ^^^^^^^^^^^ cannot borrow as mutable
|
note: the binding is already a mutable borrow
--> $DIR/issue-31424.rs:13:18
|
LL | fn bar(self: &mut Self) {
| ^^^^^^^^^
help: try removing `&mut` here
--> $DIR/issue-31424.rs:16:9
|
LL | (&mut self).bar();
| ^^^^^^^^^^^
| |
| cannot borrow as mutable
| help: try removing `&mut` here
error: aborting due to 2 previous errors; 1 warning emitted

16
src/test/ui/did_you_mean/issue-34126.stderr
View File

@ -2,10 +2,18 @@ error[E0596]: cannot borrow `self` as mutable, as it is not declared as mutable
--> $DIR/issue-34126.rs:6:18
|
LL | self.run(&mut self);
| ^^^^^^^^^
| |
| cannot borrow as mutable
| help: try removing `&mut` here
| ^^^^^^^^^ cannot borrow as mutable
|
note: the binding is already a mutable borrow
--> $DIR/issue-34126.rs:5:14
|
LL | fn start(&mut self) {
| ^^^^^^^^^
help: try removing `&mut` here
|
LL - self.run(&mut self);
LL + self.run(self);
|
error[E0502]: cannot borrow `self` as mutable because it is also borrowed as immutable
--> $DIR/issue-34126.rs:6:18

28
src/test/ui/nll/issue-51191.stderr
View File

@ -13,11 +13,19 @@ LL | (&mut self).bar();
error[E0596]: cannot borrow `self` as mutable, as it is not declared as mutable
--> $DIR/issue-51191.rs:7:9
|
LL | (&mut self).bar();
| ^^^^^^^^^^^ cannot borrow as mutable
|
note: the binding is already a mutable borrow
--> $DIR/issue-51191.rs:4:18
|
LL | fn bar(self: &mut Self) {
| ^^^^^^^^^
help: try removing `&mut` here
--> $DIR/issue-51191.rs:7:9
|
LL | (&mut self).bar();
| ^^^^^^^^^^^
| |
| cannot borrow as mutable
| help: try removing `&mut` here
error[E0596]: cannot borrow `self` as mutable, as it is not declared as mutable
--> $DIR/issue-51191.rs:13:9
@ -42,11 +50,19 @@ LL | (&mut self).bar();
error[E0596]: cannot borrow `self` as mutable, as it is not declared as mutable
--> $DIR/issue-51191.rs:28:9
|
LL | (&mut self).bar();
| ^^^^^^^^^^^ cannot borrow as mutable
|
note: the binding is already a mutable borrow
--> $DIR/issue-51191.rs:27:16
|
LL | fn mtblref(&mut self) {
| ^^^^^^^^^
help: try removing `&mut` here
--> $DIR/issue-51191.rs:28:9
|
LL | (&mut self).bar();
| ^^^^^^^^^^^
| |
| cannot borrow as mutable
| help: try removing `&mut` here
error: aborting due to 5 previous errors; 1 warning emitted