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Suggest move for closures and async blocks in more cases.

This commit is contained in:
Alex Aktsipetrov 2020-04-07 23:57:26 +02:00
parent 42abbd8878
commit aaebbe196b
9 changed files with 84 additions and 68 deletions
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58
src/librustc_mir/borrow_check/diagnostics/conflict_errors.rs
View File

@ -760,47 +760,26 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
(
Some(ref name),
BorrowExplanation::MustBeValidFor {
category: category @ ConstraintCategory::Return,
category:
category
@
(ConstraintCategory::Return
| ConstraintCategory::CallArgument
| ConstraintCategory::OpaqueType),
from_closure: false,
ref region_name,
span,
..
},
)
| (
Some(ref name),
BorrowExplanation::MustBeValidFor {
category: category @ ConstraintCategory::CallArgument,
from_closure: false,
ref region_name,
) if borrow_spans.for_generator() | borrow_spans.for_closure() => self
.report_escaping_closure_capture(
borrow_spans,
borrow_span,
region_name,
category,
span,
..
},
) if borrow_spans.for_closure() => self.report_escaping_closure_capture(
borrow_spans,
borrow_span,
region_name,
category,
span,
&format!("`{}`", name),
),
(
Some(ref name),
BorrowExplanation::MustBeValidFor {
category: category @ ConstraintCategory::OpaqueType,
from_closure: false,
ref region_name,
span,
..
},
) if borrow_spans.for_generator() => self.report_escaping_closure_capture(
borrow_spans,
borrow_span,
region_name,
category,
span,
&format!("`{}`", name),
),
&format!("`{}`", name),
),
(
ref name,
BorrowExplanation::MustBeValidFor {
@ -1187,7 +1166,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
) -> DiagnosticBuilder<'cx> {
let tcx = self.infcx.tcx;
let args_span = use_span.args_or_use();
let mut err = self.cannot_capture_in_long_lived_closure(args_span, captured_var, var_span);
let suggestion = match tcx.sess.source_map().span_to_snippet(args_span) {
Ok(mut string) => {
@ -1213,6 +1191,9 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
},
None => "closure",
};
let mut err =
self.cannot_capture_in_long_lived_closure(args_span, kind, captured_var, var_span);
err.span_suggestion(
args_span,
&format!(
@ -1225,8 +1206,9 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
);
let msg = match category {
ConstraintCategory::Return => "closure is returned here".to_string(),
ConstraintCategory::OpaqueType => "generator is returned here".to_string(),
ConstraintCategory::Return | ConstraintCategory::OpaqueType => {
format!("{} is returned here", kind)
}
ConstraintCategory::CallArgument => {
fr_name.highlight_region_name(&mut err);
format!("function requires argument type to outlive `{}`", fr_name)

1
src/librustc_mir/lib.rs
View File

@ -25,6 +25,7 @@ Rust MIR: a lowered representation of Rust.
#![feature(stmt_expr_attributes)]
#![feature(trait_alias)]
#![feature(option_expect_none)]
#![feature(or_patterns)]
#![recursion_limit = "256"]
#[macro_use]

4
src/librustc_mir/util/borrowck_errors.rs
View File

@ -431,6 +431,7 @@ impl<'cx, 'tcx> crate::borrow_check::MirBorrowckCtxt<'cx, 'tcx> {
crate fn cannot_capture_in_long_lived_closure(
&self,
closure_span: Span,
closure_kind: &str,
borrowed_path: &str,
capture_span: Span,
) -> DiagnosticBuilder<'cx> {
@ -438,9 +439,10 @@ impl<'cx, 'tcx> crate::borrow_check::MirBorrowckCtxt<'cx, 'tcx> {
self,
closure_span,
E0373,
"closure may outlive the current function, \
"{} may outlive the current function, \
but it borrows {}, \
which is owned by the current function",
closure_kind,
borrowed_path,
);
err.span_label(capture_span, format!("{} is borrowed here", borrowed_path))

12
src/test/ui/async-await/async-borrowck-escaping-block-error.fixed
View File

@ -1,12 +1,18 @@
// edition:2018
// run-rustfix
fn foo() -> Box<impl std::future::Future<Output = u32>> {
fn test_boxed() -> Box<impl std::future::Future<Output = u32>> {
let x = 0u32;
Box::new(async move { x } )
//~^ ERROR E0373
}
fn main() {
let _foo = foo();
fn test_ref(x: &u32) -> impl std::future::Future<Output = u32> + '_ {
async move { *x }
//~^ ERROR E0373
}
fn main() {
let _ = test_boxed();
let _ = test_ref(&0u32);
}

12
src/test/ui/async-await/async-borrowck-escaping-block-error.rs
View File

@ -1,12 +1,18 @@
// edition:2018
// run-rustfix
fn foo() -> Box<impl std::future::Future<Output = u32>> {
fn test_boxed() -> Box<impl std::future::Future<Output = u32>> {
let x = 0u32;
Box::new(async { x } )
//~^ ERROR E0373
}
fn main() {
let _foo = foo();
fn test_ref(x: &u32) -> impl std::future::Future<Output = u32> + '_ {
async { *x }
//~^ ERROR E0373
}
fn main() {
let _ = test_boxed();
let _ = test_ref(&0u32);
}

31
src/test/ui/async-await/async-borrowck-escaping-block-error.stderr
View File

@ -1,4 +1,4 @@
error[E0373]: closure may outlive the current function, but it borrows `x`, which is owned by the current function
error[E0373]: async block may outlive the current function, but it borrows `x`, which is owned by the current function
--> $DIR/async-borrowck-escaping-block-error.rs:6:20
|
LL | Box::new(async { x } )
@ -7,16 +7,35 @@ LL | Box::new(async { x } )
| | `x` is borrowed here
| may outlive borrowed value `x`
|
note: generator is returned here
--> $DIR/async-borrowck-escaping-block-error.rs:4:13
note: async block is returned here
--> $DIR/async-borrowck-escaping-block-error.rs:4:20
|
LL | fn foo() -> Box<impl std::future::Future<Output = u32>> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
LL | fn test_boxed() -> Box<impl std::future::Future<Output = u32>> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
help: to force the async block to take ownership of `x` (and any other referenced variables), use the `move` keyword
|
LL | Box::new(async move { x } )
| ^^^^^^^^^^
error: aborting due to previous error
error[E0373]: async block may outlive the current function, but it borrows `x`, which is owned by the current function
--> $DIR/async-borrowck-escaping-block-error.rs:11:11
|
LL | async { *x }
| ^^^-^^
| | |
| | `x` is borrowed here
| may outlive borrowed value `x`
|
note: async block is returned here
--> $DIR/async-borrowck-escaping-block-error.rs:11:5
|
LL | async { *x }
| ^^^^^^^^^^^^
help: to force the async block to take ownership of `x` (and any other referenced variables), use the `move` keyword
|
LL | async move { *x }
| ^^^^^^^^^^^
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0373`.

2
src/test/ui/async-await/async-borrowck-escaping-closure-error.rs
View File

@ -1,5 +1,5 @@
// edition:2018
#![feature(async_closure,async_await)]
#![feature(async_closure)]
fn foo() -> Box<dyn std::future::Future<Output = u32>> {
let x = 0u32;
Box::new((async || x)())

2
src/test/ui/impl-trait/does-not-live-long-enough.rs
View File

@ -4,7 +4,7 @@ struct List {
impl List {
fn started_with<'a>(&'a self, prefix: &'a str) -> impl Iterator<Item=&'a str> {
self.data.iter().filter(|s| s.starts_with(prefix)).map(|s| s.as_ref())
//~^ ERROR does not live long enough
//~^ ERROR E0373
}
}

30
src/test/ui/impl-trait/does-not-live-long-enough.stderr
View File

@ -1,21 +1,21 @@
error[E0597]: `prefix` does not live long enough
--> $DIR/does-not-live-long-enough.rs:6:51
error[E0373]: closure may outlive the current function, but it borrows `prefix`, which is owned by the current function
--> $DIR/does-not-live-long-enough.rs:6:33
|
LL | self.data.iter().filter(|s| s.starts_with(prefix)).map(|s| s.as_ref())
| ^^^ ------ `prefix` is borrowed here
| |
| may outlive borrowed value `prefix`
|
note: closure is returned here
--> $DIR/does-not-live-long-enough.rs:5:55
|
LL | fn started_with<'a>(&'a self, prefix: &'a str) -> impl Iterator<Item=&'a str> {
| -- lifetime `'a` defined here --------------------------- opaque type requires that `prefix` is borrowed for `'a`
LL | self.data.iter().filter(|s| s.starts_with(prefix)).map(|s| s.as_ref())
| --- ^^^^^^ borrowed value does not live long enough
| |
| value captured here
LL |
LL | }
| - `prefix` dropped here while still borrowed
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
help: to force the closure to take ownership of `prefix` (and any other referenced variables), use the `move` keyword
|
help: you can add a bound to the opaque type to make it last less than `'static` and match `'a`
|
LL | fn started_with<'a>(&'a self, prefix: &'a str) -> impl Iterator<Item=&'a str> + 'a {
| ^^^^
LL | self.data.iter().filter(move |s| s.starts_with(prefix)).map(|s| s.as_ref())
| ^^^^^^^^
error: aborting due to previous error
For more information about this error, try `rustc --explain E0597`.
For more information about this error, try `rustc --explain E0373`.