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NLL: On "cannot move out of type" error, print original source before rewrite.

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* Arguably this change is sometimes injecting noise into the output
   (namely in the cases where the suggested rewrite is inline with the
   suggestion and we end up highlighting the original source code).
   I would not be opposed to something more aggressive/dynamic, like
   revising the suggestion code to automatically print the original
   source when necessary (e.g. when the error does not have a span
   that includes the span of the suggestion).

 * Also, as another note on this change: The doc comment for `Diagnostic::span_suggestion`
   says:
    /// The message
    ///
    /// * should not end in any punctuation (a `:` is added automatically)
    /// * should not be a question
    /// * should not contain any parts like "the following", "as shown"

   but the `:` is *not* added when the emitted line appears
   out-of-line relative to the suggestion. I find that to be an
   unfortunate UI experience.

----

As a drive-by fix, also changed code to combine multiple suggestions
for a pattern into a single multipart suggestion (which vastly
improves user experience IMO).

----

Includes the updates to expected NLL diagnostics.
This commit is contained in:
Felix S. Klock II 2018-07-31 17:22:12 +02:00
parent 8961132010
commit a5a3f765eb
8 changed files with 86 additions and 44 deletions
Download patch file Download diff file Expand all files Collapse all files

17
src/librustc_mir/borrow_check/move_errors.rs
View file

@ -341,7 +341,8 @@ impl<'a, 'gcx, 'tcx> MirBorrowckCtxt<'a, 'gcx, 'tcx> {
// another match arm
binds_to.sort();
binds_to.dedup();
for local in binds_to {
let mut multipart_suggestion = Vec::with_capacity(binds_to.len());
for (j, local) in binds_to.into_iter().enumerate() {
let bind_to = &self.mir.local_decls[local];
let binding_span = bind_to.source_info.span;
@ -350,13 +351,15 @@ impl<'a, 'gcx, 'tcx> MirBorrowckCtxt<'a, 'gcx, 'tcx> {
Mutability::Not => "ref",
Mutability::Mut => "ref mut",
};
if j == 0 {
err.span_label(binding_span, format!("data moved here"));
} else {
err.span_label(binding_span, format!("... and here"));
}
match bind_to.name {
Some(name) => {
err.span_suggestion(
binding_span,
"to prevent move, use ref or ref mut",
format!("{} {:?}", ref_kind, name),
);
multipart_suggestion.push((binding_span,
format!("{} {}", ref_kind, name)));
}
None => {
err.span_label(
@ -366,6 +369,8 @@ impl<'a, 'gcx, 'tcx> MirBorrowckCtxt<'a, 'gcx, 'tcx> {
}
}
}
err.multipart_suggestion("to prevent move, use ref or ref mut",
multipart_suggestion);
}
// Nothing to suggest.
GroupedMoveError::OtherIllegalMove { .. } => (),

10
src/test/ui/borrowck/borrowck-move-error-with-note.nll.stderr
View file

@ -19,14 +19,16 @@ error[E0509]: cannot move out of type `S`, which implements the `Drop` trait
|
LL | match (S {f: "foo".to_string(), g: "bar".to_string()}) {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot move out of here
...
LL | f: _s,
| -- data moved here
LL | g: _t
| -- ... and here
help: to prevent move, use ref or ref mut
|
LL | f: ref _s,
| ^^^^^^
help: to prevent move, use ref or ref mut
|
LL | g: ref _t
| ^^^^^^
|
error[E0507]: cannot move out of borrowed content
--> $DIR/borrowck-move-error-with-note.rs:57:11

13
src/test/ui/borrowck/borrowck-move-out-of-vec-tail.nll.stderr
View file

@ -3,14 +3,19 @@ error[E0508]: cannot move out of type `[Foo]`, a non-copy slice
|
LL | match tail {
| ^^^^ cannot move out of here
LL | &[Foo { string: a },
| - data moved here
...
LL | Foo { string: b }] => {
| - ... and here
help: to prevent move, use ref or ref mut
|
LL | &[Foo { string: ref a },
| ^^^^^
help: to prevent move, use ref or ref mut
|
LL | //~^ ERROR cannot move out of type `[Foo]`
LL | //~| cannot move out
LL | //~| to prevent move
LL | Foo { string: ref b }] => {
| ^^^^^
|
error: aborting due to previous error

27
src/test/ui/borrowck/borrowck-vec-pattern-nesting.nll.stderr
View file

@ -28,7 +28,10 @@ error[E0508]: cannot move out of type `[std::boxed::Box<isize>]`, a non-copy sli
LL | match vec {
| ^^^ cannot move out of here
LL | &mut [_a, //~ ERROR cannot move out
| -- help: to prevent move, use ref or ref mut: `ref _a`
| --
| |
| data moved here
| help: to prevent move, use ref or ref mut: `ref _a`
error[E0508]: cannot move out of type `[std::boxed::Box<isize>]`, a non-copy slice
--> $DIR/borrowck-vec-pattern-nesting.rs:57:13
@ -46,7 +49,10 @@ LL | match vec {
| ^^^ cannot move out of here
...
LL | _b] => {}
| -- help: to prevent move, use ref or ref mut: `ref _b`
| --
| |
| data moved here
| help: to prevent move, use ref or ref mut: `ref _b`
error[E0508]: cannot move out of type `[std::boxed::Box<isize>]`, a non-copy slice
--> $DIR/borrowck-vec-pattern-nesting.rs:70:13
@ -62,18 +68,15 @@ error[E0508]: cannot move out of type `[std::boxed::Box<isize>]`, a non-copy sli
|
LL | match vec {
| ^^^ cannot move out of here
LL | &mut [_a, _b, _c] => {} //~ ERROR cannot move out
| -- -- -- ... and here
| | |
| | ... and here
| data moved here
help: to prevent move, use ref or ref mut
|
LL | &mut [ref _a, _b, _c] => {} //~ ERROR cannot move out
| ^^^^^^
help: to prevent move, use ref or ref mut
|
LL | &mut [_a, ref _b, _c] => {} //~ ERROR cannot move out
| ^^^^^^
help: to prevent move, use ref or ref mut
|
LL | &mut [_a, _b, ref _c] => {} //~ ERROR cannot move out
| ^^^^^^
LL | &mut [ref _a, ref _b, ref _c] => {} //~ ERROR cannot move out
| ^^^^^^ ^^^^^^ ^^^^^^
error[E0508]: cannot move out of type `[std::boxed::Box<isize>]`, a non-copy slice
--> $DIR/borrowck-vec-pattern-nesting.rs:82:13

1
src/test/ui/borrowck/issue-51415.nll.stderr
View file

@ -4,6 +4,7 @@ error[E0507]: cannot move out of borrowed content
LL | let opt = a.iter().enumerate().find(|(_, &s)| {
| ^^^^^-^
| | |
| | data moved here
| | help: to prevent move, use ref or ref mut: `ref s`
| cannot move out of borrowed content

5
src/test/ui/codemap_tests/overlapping_spans.nll.stderr
View file

@ -4,7 +4,10 @@ error[E0509]: cannot move out of type `S`, which implements the `Drop` trait
LL | match (S {f:"foo".to_string()}) {
| ^^^^^^^^^^^^^^^^^^^^^^^^^ cannot move out of here
LL | S {f:_s} => {} //~ ERROR cannot move out
| -- help: to prevent move, use ref or ref mut: `ref _s`
| --
| |
| data moved here
| help: to prevent move, use ref or ref mut: `ref _s`
error: aborting due to previous error

28
src/test/ui/issue-12567.nll.stderr
View file

@ -3,28 +3,40 @@ error[E0508]: cannot move out of type `[T]`, a non-copy slice
|
LL | match (l1, l2) {
| ^^^^^^^^ cannot move out of here
LL | (&[], &[]) => println!("both empty"),
LL | (&[], &[hd, ..]) | (&[hd, ..], &[])
| -- data moved here
...
LL | (&[hd1, ..], &[hd2, ..])
| --- ... and here
help: to prevent move, use ref or ref mut
|
LL | (&[], &[ref hd, ..]) | (&[hd, ..], &[])
| ^^^^^^
help: to prevent move, use ref or ref mut
|
LL | => println!("one empty"),
LL | //~^^ ERROR: cannot move out of type `[T]`, a non-copy slice
LL | //~^^^ ERROR: cannot move out of type `[T]`, a non-copy slice
LL | (&[hd1, ..], &[ref hd2, ..])
| ^^^^^^^
|
error[E0508]: cannot move out of type `[T]`, a non-copy slice
--> $DIR/issue-12567.rs:14:11
|
LL | match (l1, l2) {
| ^^^^^^^^ cannot move out of here
LL | (&[], &[]) => println!("both empty"),
LL | (&[], &[hd, ..]) | (&[hd, ..], &[])
| -- data moved here
...
LL | (&[hd1, ..], &[hd2, ..])
| --- ... and here
help: to prevent move, use ref or ref mut
|
LL | (&[], &[ref hd, ..]) | (&[hd, ..], &[])
| ^^^^^^
help: to prevent move, use ref or ref mut
|
LL | => println!("one empty"),
LL | //~^^ ERROR: cannot move out of type `[T]`, a non-copy slice
LL | //~^^^ ERROR: cannot move out of type `[T]`, a non-copy slice
LL | (&[ref hd1, ..], &[hd2, ..])
| ^^^^^^^
|
error: aborting due to 2 previous errors

29
src/test/ui/nll/move-errors.stderr
View file

@ -59,6 +59,7 @@ error[E0509]: cannot move out of type `D`, which implements the `Drop` trait
LL | let C(D(s)) = c;
| - ^ cannot move out of here
| |
| data moved here
| help: to prevent move, use ref or ref mut: `ref s`
error[E0507]: cannot move out of borrowed content
@ -88,7 +89,10 @@ LL | match x {
| ^ cannot move out of here
...
LL | B::U(D(s)) => (),
| - help: to prevent move, use ref or ref mut: `ref s`
| -
| |
| data moved here
| help: to prevent move, use ref or ref mut: `ref s`
error[E0509]: cannot move out of type `D`, which implements the `Drop` trait
--> $DIR/move-errors.rs:105:11
@ -97,7 +101,10 @@ LL | match x {
| ^ cannot move out of here
...
LL | (D(s), &t) => (),
| - help: to prevent move, use ref or ref mut: `ref s`
| -
| |
| data moved here
| help: to prevent move, use ref or ref mut: `ref s`
error[E0507]: cannot move out of borrowed content
--> $DIR/move-errors.rs:105:11
@ -106,21 +113,25 @@ LL | match x {
| ^ cannot move out of borrowed content
...
LL | (D(s), &t) => (),
| - help: to prevent move, use ref or ref mut: `ref t`
| -
| |
| data moved here
| help: to prevent move, use ref or ref mut: `ref t`
error[E0509]: cannot move out of type `F`, which implements the `Drop` trait
--> $DIR/move-errors.rs:115:11
|
LL | match x {
| ^ cannot move out of here
LL | //~^ ERROR
LL | F(s, mut t) => (),
| - ----- ... and here
| |
| data moved here
help: to prevent move, use ref or ref mut
|
LL | F(ref s, mut t) => (),
| ^^^^^
help: to prevent move, use ref or ref mut
|
LL | F(s, ref mut t) => (),
| ^^^^^^^^^
LL | F(ref s, ref mut t) => (),
| ^^^^^ ^^^^^^^^^
error[E0507]: cannot move out of borrowed content
--> $DIR/move-errors.rs:123:11