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Auto merge of #52678 - matthewjasper:better-spans, r=nikomatsakis

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[NLL] Use better spans in some errors

* Use the span of the discriminant and patterns for "fake" statements created to properly check matches. I plan to special case these soon, but this felt like a good first step
* Use the span of the statement, rather than the initialization, when reporting move errors for `let x = ...`, which avoids giving an unhelpful suggestion to use `&{ }`.

r? @nikomatsakis cc @pnkfelix
This commit is contained in:
bors 2018-07-28 07:42:13 +00:00
commit 0560747652
15 changed files with 295 additions and 162 deletions
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43
src/librustc_mir/borrow_check/move_errors.rs
View file

@ -87,6 +87,10 @@ impl<'a, 'gcx, 'tcx> MirBorrowckCtxt<'a, 'gcx, 'tcx> {
cannot_move_out_of: IllegalMoveOrigin { location, kind },
} => {
let stmt_source_info = self.mir.source_info(location);
// Note: that the only time we assign a place isn't a temporary
// to a user variable is when initializing it.
// If that ever stops being the case, then the ever initialized
// flow could be used.
if let Some(StatementKind::Assign(
Place::Local(local),
Rvalue::Use(Operand::Move(move_from)),
@ -109,26 +113,16 @@ impl<'a, 'gcx, 'tcx> MirBorrowckCtxt<'a, 'gcx, 'tcx> {
opt_ty_info: _,
}))) = local_decl.is_user_variable
{
// HACK use scopes to determine if this assignment is
// the initialization of a variable.
// FIXME(matthewjasper) This would probably be more
// reliable if it used the ever initialized dataflow
// but move errors are currently reported before the
// rest of borrowck has run.
if self
.mir
.is_sub_scope(local_decl.source_info.scope, stmt_source_info.scope)
{
self.append_binding_error(
grouped_errors,
kind,
move_from,
*local,
opt_match_place,
match_span,
);
return;
}
self.append_binding_error(
grouped_errors,
kind,
move_from,
*local,
opt_match_place,
match_span,
stmt_source_info.span,
);
return;
}
}
grouped_errors.push(GroupedMoveError::OtherIllegalMove {
@ -147,6 +141,7 @@ impl<'a, 'gcx, 'tcx> MirBorrowckCtxt<'a, 'gcx, 'tcx> {
bind_to: Local,
match_place: &Option<Place<'tcx>>,
match_span: Span,
statement_span: Span,
) {
debug!(
"append_to_grouped_errors(match_place={:?}, match_span={:?})",
@ -173,13 +168,13 @@ impl<'a, 'gcx, 'tcx> MirBorrowckCtxt<'a, 'gcx, 'tcx> {
debug!("found a new move error location");
// Don't need to point to x in let x = ... .
let binds_to = if from_simple_let {
vec![]
let (binds_to, span) = if from_simple_let {
(vec![], statement_span)
} else {
vec![bind_to]
(vec![bind_to], match_span)
};
grouped_errors.push(GroupedMoveError::MovesFromMatchPlace {
span: match_span,
span,
move_from: match_place.clone(),
kind,
binds_to,

8
src/librustc_mir/build/matches/mod.rs
View file

@ -63,13 +63,13 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
// injects a borrow of the matched input, which should have the same effect
// as eddyb's hack. Once NLL is the default, we can remove the hack.
let dummy_source_info = self.source_info(span);
let dummy_source_info = self.source_info(discriminant_span);
let dummy_access = Rvalue::Discriminant(discriminant_place.clone());
let dummy_ty = dummy_access.ty(&self.local_decls, tcx);
let dummy_temp = self.temp(dummy_ty, dummy_source_info.span);
self.cfg.push_assign(block, dummy_source_info, &dummy_temp, dummy_access);
let source_info = self.source_info(span);
let source_info = self.source_info(discriminant_span);
let borrowed_input_temp = if tcx.generate_borrow_of_any_match_input() {
// The region is unknown at this point; we rely on NLL
// inference to find an appropriate one. Therefore you can
@ -136,9 +136,9 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
// This should ensure that you cannot change
// the variant for an enum while you are in
// the midst of matching on it.
let pattern_source_info = self.source_info(pattern.span);
self.cfg.push(*pre_binding_block, Statement {
source_info,
source_info: pattern_source_info,
kind: StatementKind::ReadForMatch(borrow_temp.clone()),
});
}

24
src/test/ui/borrowck/issue-41962.stderr
View file

@ -17,26 +17,22 @@ LL | if let Some(thing) = maybe {
= note: move occurs because the value has type `std::vec::Vec<bool>`, which does not implement the `Copy` trait
error[E0382]: use of moved value: `maybe` (Mir)
--> $DIR/issue-41962.rs:17:9
--> $DIR/issue-41962.rs:17:30
|
LL | if let Some(thing) = maybe {
| ^ ----- value moved here
| _________|
| |
LL | | }
| |_________^ value used here after move
LL | if let Some(thing) = maybe {
| ----- ^^^^^ value used here after move
| |
| value moved here
|
= note: move occurs because value has type `std::vec::Vec<bool>`, which does not implement the `Copy` trait
error[E0382]: borrow of moved value: `maybe` (Mir)
--> $DIR/issue-41962.rs:17:9
--> $DIR/issue-41962.rs:17:30
|
LL | if let Some(thing) = maybe {
| ^ ----- value moved here
| _________|
| |
LL | | }
| |_________^ value borrowed here after move
LL | if let Some(thing) = maybe {
| ----- ^^^^^ value borrowed here after move
| |
| value moved here
|
= note: move occurs because value has type `std::vec::Vec<bool>`, which does not implement the `Copy` trait

52
src/test/ui/issue-17385.nll.stderr
View file

@ -1,26 +1,20 @@
error[E0382]: use of moved value: `foo`
--> $DIR/issue-17385.rs:28:5
--> $DIR/issue-17385.rs:28:11
|
LL | drop(foo);
| --- value moved here
LL | / match foo { //~ ERROR use of moved value
LL | | X(1) => (),
LL | | _ => unreachable!()
LL | | }
| |_____^ value used here after move
LL | drop(foo);
| --- value moved here
LL | match foo { //~ ERROR use of moved value
| ^^^ value used here after move
|
= note: move occurs because `foo` has type `X`, which does not implement the `Copy` trait
error[E0382]: borrow of moved value: `foo`
--> $DIR/issue-17385.rs:28:5
--> $DIR/issue-17385.rs:28:11
|
LL | drop(foo);
| --- value moved here
LL | / match foo { //~ ERROR use of moved value
LL | | X(1) => (),
LL | | _ => unreachable!()
LL | | }
| |_____^ value borrowed here after move
LL | drop(foo);
| --- value moved here
LL | match foo { //~ ERROR use of moved value
| ^^^ value borrowed here after move
|
= note: move occurs because `foo` has type `X`, which does not implement the `Copy` trait
@ -36,28 +30,22 @@ LL | X(1) => (),
= note: move occurs because `foo` has type `X`, which does not implement the `Copy` trait
error[E0382]: use of moved value: `e`
--> $DIR/issue-17385.rs:35:5
--> $DIR/issue-17385.rs:35:11
|
LL | drop(e);
| - value moved here
LL | / match e { //~ ERROR use of moved value
LL | | Enum::Variant1 => unreachable!(),
LL | | Enum::Variant2 => ()
LL | | }
| |_____^ value used here after move
LL | drop(e);
| - value moved here
LL | match e { //~ ERROR use of moved value
| ^ value used here after move
|
= note: move occurs because `e` has type `Enum`, which does not implement the `Copy` trait
error[E0382]: borrow of moved value: `e`
--> $DIR/issue-17385.rs:35:5
--> $DIR/issue-17385.rs:35:11
|
LL | drop(e);
| - value moved here
LL | / match e { //~ ERROR use of moved value
LL | | Enum::Variant1 => unreachable!(),
LL | | Enum::Variant2 => ()
LL | | }
| |_____^ value borrowed here after move
LL | drop(e);
| - value moved here
LL | match e { //~ ERROR use of moved value
| ^ value borrowed here after move
|
= note: move occurs because `e` has type `Enum`, which does not implement the `Copy` trait

20
src/test/ui/issue-20801.nll.stderr
View file

@ -2,25 +2,37 @@ error[E0507]: cannot move out of borrowed content
--> $DIR/issue-20801.rs:36:22
|
LL | let a = unsafe { *mut_ref() };
| ^^^^^^^^^^ cannot move out of borrowed content
| ^^^^^^^^^^
| |
| cannot move out of borrowed content
| help: consider using a reference instead: `&*mut_ref()`
error[E0507]: cannot move out of borrowed content
--> $DIR/issue-20801.rs:39:22
|
LL | let b = unsafe { *imm_ref() };
| ^^^^^^^^^^ cannot move out of borrowed content
| ^^^^^^^^^^
| |
| cannot move out of borrowed content
| help: consider using a reference instead: `&*imm_ref()`
error[E0507]: cannot move out of borrowed content
--> $DIR/issue-20801.rs:42:22
|
LL | let c = unsafe { *mut_ptr() };
| ^^^^^^^^^^ cannot move out of borrowed content
| ^^^^^^^^^^
| |
| cannot move out of borrowed content
| help: consider using a reference instead: `&*mut_ptr()`
error[E0507]: cannot move out of borrowed content
--> $DIR/issue-20801.rs:45:22
|
LL | let d = unsafe { *const_ptr() };
| ^^^^^^^^^^^^ cannot move out of borrowed content
| ^^^^^^^^^^^^
| |
| cannot move out of borrowed content
| help: consider using a reference instead: `&*const_ptr()`
error: aborting due to 4 previous errors

23
src/test/ui/issue-27282-move-match-input-into-guard.stderr
View file

@ -1,21 +1,14 @@
error[E0505]: cannot move out of `b` because it is borrowed
--> $DIR/issue-27282-move-match-input-into-guard.rs:26:16
|
LL | match b {
| _____-
| |_____|
| ||
LL | || &mut false => {},
LL | || _ if { (|| { let bar = b; *bar = false; })();
| || ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ move out of `b` occurs here
LL | || //~^ ERROR cannot move out of `b` because it is borrowed [E0505]
... ||
LL | || _ => panic!("surely we could never get here, since rustc warns it is unreachable."),
LL | || }
| || -
| ||_____|
| |______borrow of `b` occurs here
| borrow later used here
LL | match b {
| - borrow of `b` occurs here
LL | &mut false => {},
LL | _ if { (|| { let bar = b; *bar = false; })();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ move out of `b` occurs here
...
LL | &mut true => { println!("You might think we should get here"); },
| --------- borrow later used here
error[E0382]: use of moved value: `*b`
--> $DIR/issue-27282-move-match-input-into-guard.rs:29:14

28
src/test/ui/issue-27282-mutate-before-diverging-arm-1.stderr
View file

@ -1,24 +1,16 @@
error[E0500]: closure requires unique access to `x` but it is already borrowed
--> $DIR/issue-27282-mutate-before-diverging-arm-1.rs:33:14
|
LL | match x {
| _____-
| |_____|
| ||
LL | || &mut None => panic!("unreachable"),
LL | || &mut Some(&_) if {
LL | || // ForceFnOnce needed to exploit #27282
LL | || (|| { *x = None; drop(force_fn_once); })();
| || ^^ - borrow occurs due to use of `x` in closure
| || |
| || closure construction occurs here
... ||
LL | || _ => panic!("unreachable"),
LL | || }
| || -
| ||_____|
| |______borrow occurs here
| borrow later used here
LL | match x {
| - borrow occurs here
...
LL | (|| { *x = None; drop(force_fn_once); })();
| ^^ - borrow occurs due to use of `x` in closure
| |
| closure construction occurs here
...
LL | &mut Some(&a) if { // this binds to garbage if we've corrupted discriminant
| ------------- borrow later used here
error: aborting due to previous error

29
src/test/ui/issue-27282-mutate-before-diverging-arm-2.stderr
View file

@ -1,25 +1,16 @@
error[E0500]: closure requires unique access to `x` but it is already borrowed
--> $DIR/issue-27282-mutate-before-diverging-arm-2.rs:38:18
|
LL | match x {
| _____-
| |_____|
| ||
LL | || &mut None => panic!("unreachable"),
LL | || &mut Some(&_)
LL | || if {
LL | || // ForceFnOnce needed to exploit #27282
LL | || (|| { *x = None; drop(force_fn_once); })();
| || ^^ - borrow occurs due to use of `x` in closure
| || |
| || closure construction occurs here
... ||
LL | || _ => panic!("unreachable"),
LL | || }
| || -
| ||_____|
| |______borrow occurs here
| borrow later used here
LL | match x {
| - borrow occurs here
...
LL | (|| { *x = None; drop(force_fn_once); })();
| ^^ - borrow occurs due to use of `x` in closure
| |
| closure construction occurs here
...
LL | &mut Some(&2)
| ------------- borrow later used here
error: aborting due to previous error

8
src/test/ui/issue-47412.stderr
View file

@ -1,16 +1,16 @@
error[E0133]: access to union field is unsafe and requires unsafe function or block
--> $DIR/issue-47412.rs:21:5
--> $DIR/issue-47412.rs:21:11
|
LL | match u.void {}
| ^^^^^^^^^^^^^^^ access to union field
| ^^^^^^ access to union field
|
= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
error[E0133]: dereference of raw pointer is unsafe and requires unsafe function or block
--> $DIR/issue-47412.rs:27:5
--> $DIR/issue-47412.rs:27:11
|
LL | match *ptr {}
| ^^^^^^^^^^^^^ dereference of raw pointer
| ^^^^ dereference of raw pointer
|
= note: raw pointers may be NULL, dangling or unaligned; they can violate aliasing rules and cause data races: all of these are undefined behavior

16
src/test/ui/lifetime-errors/ex1-return-one-existing-name-early-bound-in-struct.nll.stderr
View file

@ -5,18 +5,12 @@ LL | other //~ ERROR explicit lifetime
| ^^^^^
error[E0621]: explicit lifetime required in the type of `other`
--> $DIR/ex1-return-one-existing-name-early-bound-in-struct.rs:18:9
--> $DIR/ex1-return-one-existing-name-early-bound-in-struct.rs:18:15
|
LL | fn bar(&self, other: Foo) -> Foo<'a> {
| ----- consider changing the type of `other` to `Foo<'a>`
LL | / match *self {
LL | | Foo::Bar(s) => {
LL | | if s == "test" {
LL | | other //~ ERROR explicit lifetime
... |
LL | | }
LL | | }
| |_________^ lifetime `'a` required
LL | fn bar(&self, other: Foo) -> Foo<'a> {
| ----- consider changing the type of `other` to `Foo<'a>`
LL | match *self {
| ^^^^^ lifetime `'a` required
error: aborting due to previous error

21
src/test/ui/nll/borrowed-match-issue-45045.stderr
View file

@ -1,17 +1,14 @@
error[E0503]: cannot use `e` because it was mutably borrowed
--> $DIR/borrowed-match-issue-45045.rs:24:5
--> $DIR/borrowed-match-issue-45045.rs:24:11
|
LL | let f = &mut e;
| ------ borrow of `e` occurs here
LL | let g = f;
LL | / match e { //~ cannot use `e` because it was mutably borrowed [E0503]
LL | | Xyz::A => println!("a"),
LL | | //~^ cannot use `e` because it was mutably borrowed [E0503]
LL | | Xyz::B => println!("b"),
LL | | };
| |_____^ use of borrowed `e`
LL | *g = Xyz::B;
| ----------- borrow later used here
LL | let f = &mut e;
| ------ borrow of `e` occurs here
LL | let g = f;
LL | match e { //~ cannot use `e` because it was mutably borrowed [E0503]
| ^ use of borrowed `e`
...
LL | *g = Xyz::B;
| ----------- borrow later used here
error[E0503]: cannot use `e` because it was mutably borrowed
--> $DIR/borrowed-match-issue-45045.rs:25:9

85
src/test/ui/nll/cannot-move-block-spans.nll.stderr Normal file
View file

@ -0,0 +1,85 @@
error[E0507]: cannot move out of borrowed content
--> $DIR/cannot-move-block-spans.rs:15:15
|
LL | let x = { *r }; //~ ERROR
| ^^
| |
| cannot move out of borrowed content
| help: consider removing this dereference operator: `r`
error[E0507]: cannot move out of borrowed content
--> $DIR/cannot-move-block-spans.rs:16:22
|
LL | let y = unsafe { *r }; //~ ERROR
| ^^
| |
| cannot move out of borrowed content
| help: consider removing this dereference operator: `r`
error[E0507]: cannot move out of borrowed content
--> $DIR/cannot-move-block-spans.rs:17:26
|
LL | let z = loop { break *r; }; //~ ERROR
| ^^
| |
| cannot move out of borrowed content
| help: consider removing this dereference operator: `r`
error[E0508]: cannot move out of type `[std::string::String; 2]`, a non-copy array
--> $DIR/cannot-move-block-spans.rs:21:15
|
LL | let x = { arr[0] }; //~ ERROR
| ^^^^^^
| |
| cannot move out of here
| help: consider using a reference instead: `&arr[0]`
error[E0508]: cannot move out of type `[std::string::String; 2]`, a non-copy array
--> $DIR/cannot-move-block-spans.rs:22:22
|
LL | let y = unsafe { arr[0] }; //~ ERROR
| ^^^^^^
| |
| cannot move out of here
| help: consider using a reference instead: `&arr[0]`
error[E0508]: cannot move out of type `[std::string::String; 2]`, a non-copy array
--> $DIR/cannot-move-block-spans.rs:23:26
|
LL | let z = loop { break arr[0]; }; //~ ERROR
| ^^^^^^
| |
| cannot move out of here
| help: consider using a reference instead: `&arr[0]`
error[E0507]: cannot move out of borrowed content
--> $DIR/cannot-move-block-spans.rs:27:38
|
LL | let x = { let mut u = 0; u += 1; *r }; //~ ERROR
| ^^
| |
| cannot move out of borrowed content
| help: consider removing this dereference operator: `r`
error[E0507]: cannot move out of borrowed content
--> $DIR/cannot-move-block-spans.rs:28:45
|
LL | let y = unsafe { let mut u = 0; u += 1; *r }; //~ ERROR
| ^^
| |
| cannot move out of borrowed content
| help: consider removing this dereference operator: `r`
error[E0507]: cannot move out of borrowed content
--> $DIR/cannot-move-block-spans.rs:29:49
|
LL | let z = loop { let mut u = 0; u += 1; break *r; u += 2; }; //~ ERROR
| ^^
| |
| cannot move out of borrowed content
| help: consider removing this dereference operator: `r`
error: aborting due to 9 previous errors
Some errors occurred: E0507, E0508.
For more information about an error, try `rustc --explain E0507`.

32
src/test/ui/nll/cannot-move-block-spans.rs Normal file
View file

@ -0,0 +1,32 @@
// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// Test that the we point to the inner expression when moving out to initialize
// a variable, and that we don't give a useless suggestion such as &{ *r }.
pub fn deref(r: &String) {
let x = { *r }; //~ ERROR
let y = unsafe { *r }; //~ ERROR
let z = loop { break *r; }; //~ ERROR
}
pub fn index(arr: [String; 2]) {
let x = { arr[0] }; //~ ERROR
let y = unsafe { arr[0] }; //~ ERROR
let z = loop { break arr[0]; }; //~ ERROR
}
pub fn additional_statement_cases(r: &String) {
let x = { let mut u = 0; u += 1; *r }; //~ ERROR
let y = unsafe { let mut u = 0; u += 1; *r }; //~ ERROR
let z = loop { let mut u = 0; u += 1; break *r; u += 2; }; //~ ERROR
}
fn main() {}

58
src/test/ui/nll/cannot-move-block-spans.stderr Normal file
View file

@ -0,0 +1,58 @@
error[E0507]: cannot move out of borrowed content
--> $DIR/cannot-move-block-spans.rs:15:15
|
LL | let x = { *r }; //~ ERROR
| ^^ cannot move out of borrowed content
error[E0507]: cannot move out of borrowed content
--> $DIR/cannot-move-block-spans.rs:16:22
|
LL | let y = unsafe { *r }; //~ ERROR
| ^^ cannot move out of borrowed content
error[E0507]: cannot move out of borrowed content
--> $DIR/cannot-move-block-spans.rs:17:26
|
LL | let z = loop { break *r; }; //~ ERROR
| ^^ cannot move out of borrowed content
error[E0508]: cannot move out of type `[std::string::String; 2]`, a non-copy array
--> $DIR/cannot-move-block-spans.rs:21:15
|
LL | let x = { arr[0] }; //~ ERROR
| ^^^^^^ cannot move out of here
error[E0508]: cannot move out of type `[std::string::String; 2]`, a non-copy array
--> $DIR/cannot-move-block-spans.rs:22:22
|
LL | let y = unsafe { arr[0] }; //~ ERROR
| ^^^^^^ cannot move out of here
error[E0508]: cannot move out of type `[std::string::String; 2]`, a non-copy array
--> $DIR/cannot-move-block-spans.rs:23:26
|
LL | let z = loop { break arr[0]; }; //~ ERROR
| ^^^^^^ cannot move out of here
error[E0507]: cannot move out of borrowed content
--> $DIR/cannot-move-block-spans.rs:27:38
|
LL | let x = { let mut u = 0; u += 1; *r }; //~ ERROR
| ^^ cannot move out of borrowed content
error[E0507]: cannot move out of borrowed content
--> $DIR/cannot-move-block-spans.rs:28:45
|
LL | let y = unsafe { let mut u = 0; u += 1; *r }; //~ ERROR
| ^^ cannot move out of borrowed content
error[E0507]: cannot move out of borrowed content
--> $DIR/cannot-move-block-spans.rs:29:49
|
LL | let z = loop { let mut u = 0; u += 1; break *r; u += 2; }; //~ ERROR
| ^^ cannot move out of borrowed content
error: aborting due to 9 previous errors
Some errors occurred: E0507, E0508.
For more information about an error, try `rustc --explain E0507`.

10
src/test/ui/span/issue-40157.nll.stderr
View file

@ -2,11 +2,11 @@ error[E0597]: `foo` does not live long enough
--> $DIR/issue-40157.rs:12:53
|
LL | {println!("{:?}", match { let foo = vec![1, 2]; foo.get(1) } { x => x });}
| ------------------------------^^^--------------------
| | | |
| | | `foo` dropped here while still borrowed
| | borrowed value does not live long enough
| borrow later used here
| ------------------------^^^---------
| | | |
| | | `foo` dropped here while still borrowed
| | borrowed value does not live long enough
| borrow later used here
error: aborting due to previous error