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reverse binding order in matches ...
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... to allow the subbinding of copyable fields in bindings after `@`

Fixes #69971
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@vn-ki
vn-ki committed Nov 1, 2020
1 parent 0d33ab7 commit c93d25b
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Showing 21 changed files with 641 additions and 709 deletions.
15 changes: 14 additions & 1 deletion compiler/rustc_mir_build/src/build/matches/simplify.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -131,7 +131,20 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
}

PatKind::Binding { name, mutability, mode, var, ty, ref subpattern, is_primary: _ } => {
candidate.bindings.push(Binding {
// issue #69971: the binding order should be right to left if there are more
// bindings after `@` to please the borrow checker
// Ex
// struct NonCopyStruct {
// copy_field: u32,
// }
//
// fn foo1(x: NonCopyStruct) {
// let y @ NonCopyStruct { copy_field: z } = x;
// // the above should turn into
// let z = x.copy_field;
// let y = x;
// }
candidate.bindings.insert(0, Binding {
name,
mutability,
span: match_pair.pattern.span,
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4 changes: 2 additions & 2 deletions .../ui/pattern/bindings-after-at/bind-by-move-neither-can-live-while-the-other-survives-1.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,28 +12,28 @@ fn main() {
let x = Some(X { x: () });
match x {
Some(ref _y @ _z) => {} //~ ERROR cannot move out of value because it is borrowed
//~| ERROR borrow of moved value
None => panic!(),
}

let x = Some(X { x: () });
match x {
Some(_z @ ref _y) => {}
//~^ ERROR borrow of moved value
//~| ERROR borrow of moved value
None => panic!(),
}

let mut x = Some(X { x: () });
match x {
Some(ref mut _y @ _z) => {} //~ ERROR cannot move out of value because it is borrowed
//~| ERROR borrow of moved value
None => panic!(),
}

let mut x = Some(X { x: () });
match x {
Some(_z @ ref mut _y) => {}
//~^ ERROR borrow of moved value
//~| ERROR borrow of moved value
None => panic!(),
}
}
36 changes: 18 additions & 18 deletions ...pattern/bindings-after-at/bind-by-move-neither-can-live-while-the-other-survives-1.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,7 @@ LL | Some(ref _y @ _z) => {}
| value borrowed, by `_y`, here

error: borrow of moved value
--> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:20:14
--> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:21:14
|
LL | Some(_z @ ref _y) => {}
| --^^^------
Expand All @@ -27,7 +27,7 @@ LL | Some(ref mut _y @ _z) => {}
| value borrowed, by `_y`, here

error: borrow of moved value
--> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:34:14
--> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:35:14
|
LL | Some(_z @ ref mut _y) => {}
| --^^^----------
Expand All @@ -37,34 +37,34 @@ LL | Some(_z @ ref mut _y) => {}
| move occurs because `_z` has type `X` which does not implement the `Copy` trait

error[E0382]: borrow of moved value
--> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:20:19
--> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:14:14
|
LL | Some(_z @ ref _y) => {}
| -----^^^^^^
| | |
| | value borrowed here after move
| value moved here
LL | Some(ref _y @ _z) => {}
| ^^^^^^^^^--
| | |
| | value moved here
| value borrowed here after move
|
= note: move occurs because value has type `X`, which does not implement the `Copy` trait
help: borrow this field in the pattern to avoid moving `x.0`
|
LL | Some(ref _z @ ref _y) => {}
| ^^^
LL | Some(ref _y @ ref _z) => {}
| ^^^

error[E0382]: borrow of moved value
--> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:34:19
--> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:28:14
|
LL | Some(_z @ ref mut _y) => {}
| -----^^^^^^^^^^
| | |
| | value borrowed here after move
| value moved here
LL | Some(ref mut _y @ _z) => {}
| ^^^^^^^^^^^^^--
| | |
| | value moved here
| value borrowed here after move
|
= note: move occurs because value has type `X`, which does not implement the `Copy` trait
help: borrow this field in the pattern to avoid moving `x.0`
|
LL | Some(ref _z @ ref mut _y) => {}
| ^^^
LL | Some(ref mut _y @ ref _z) => {}
| ^^^

error: aborting due to 6 previous errors

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2 changes: 1 addition & 1 deletion src/test/ui/pattern/bindings-after-at/bind-by-move-no-subbindings-fun-param.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@ fn main() {}
struct A(Box<u8>);

fn f(a @ A(u): A) -> Box<u8> {
//~^ ERROR use of moved value
//~^ ERROR use of partially moved value
drop(a);
u
}
13 changes: 7 additions & 6 deletions src/test/ui/pattern/bindings-after-at/bind-by-move-no-subbindings-fun-param.stderr
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Original file line number Diff line number Diff line change
@@ -1,12 +1,13 @@
error[E0382]: use of moved value
--> $DIR/bind-by-move-no-subbindings-fun-param.rs:9:12
error[E0382]: use of partially moved value
--> $DIR/bind-by-move-no-subbindings-fun-param.rs:9:6
|
LL | fn f(a @ A(u): A) -> Box<u8> {
| ------^-
| ^^^^^^-^
| | |
| | value used here after move
| value moved here
| move occurs because value has type `A`, which does not implement the `Copy` trait
| | value partially moved here
| value used here after partial move
|
= note: partial move occurs because value has type `Box<u8>`, which does not implement the `Copy` trait

error: aborting due to previous error

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12 changes: 6 additions & 6 deletions src/test/ui/pattern/bindings-after-at/borrowck-move-and-move.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,22 +12,22 @@ fn main() {

let a @ b = U; //~ ERROR use of moved value

let a @ (b, c) = (U, U); //~ ERROR use of moved value
let a @ (b, c) = (U, U); //~ ERROR use of partially moved value

let a @ (b, c) = (u(), u()); //~ ERROR use of moved value
let a @ (b, c) = (u(), u()); //~ ERROR use of partially moved value

match Ok(U) {
a @ Ok(b) | a @ Err(b) => {} //~ ERROR use of moved value
//~^ ERROR use of moved value
a @ Ok(b) | a @ Err(b) => {} //~ ERROR use of partially moved value
//~^ ERROR use of partially moved value
}

fn fun(a @ b: U) {} //~ ERROR use of moved value

match [u(), u(), u(), u()] {
xs @ [a, .., b] => {} //~ ERROR use of moved value
xs @ [a, .., b] => {} //~ ERROR use of partially moved value
}

match [u(), u(), u(), u()] {
xs @ [_, ys @ .., _] => {} //~ ERROR use of moved value
xs @ [_, ys @ .., _] => {} //~ ERROR use of partially moved value
}
}
110 changes: 61 additions & 49 deletions src/test/ui/pattern/bindings-after-at/borrowck-move-and-move.stderr
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Original file line number Diff line number Diff line change
@@ -1,82 +1,94 @@
error[E0382]: use of moved value
--> $DIR/borrowck-move-and-move.rs:13:13
--> $DIR/borrowck-move-and-move.rs:13:9
|
LL | let a @ b = U;
| ----^ - move occurs because value has type `U`, which does not implement the `Copy` trait
| ^^^^- - move occurs because value has type `U`, which does not implement the `Copy` trait
| | |
| | value used here after move
| value moved here
| | value moved here
| value used here after move

error[E0382]: use of moved value
--> $DIR/borrowck-move-and-move.rs:15:17
error[E0382]: use of partially moved value
--> $DIR/borrowck-move-and-move.rs:15:9
|
LL | let a @ (b, c) = (U, U);
| --------^- ------ move occurs because value has type `(U, U)`, which does not implement the `Copy` trait
| | |
| | value used here after move
| value moved here
| ^^^^^-^^^^
| | |
| | value partially moved here
| value used here after partial move
|
= note: partial move occurs because value has type `U`, which does not implement the `Copy` trait

error[E0382]: use of moved value
--> $DIR/borrowck-move-and-move.rs:17:17
error[E0382]: use of partially moved value
--> $DIR/borrowck-move-and-move.rs:17:9
|
LL | let a @ (b, c) = (u(), u());
| --------^- ---------- move occurs because value has type `(U, U)`, which does not implement the `Copy` trait
| | |
| | value used here after move
| value moved here
| ^^^^^-^^^^
| | |
| | value partially moved here
| value used here after partial move
|
= note: partial move occurs because value has type `U`, which does not implement the `Copy` trait

error[E0382]: use of moved value
--> $DIR/borrowck-move-and-move.rs:20:16
error[E0382]: use of partially moved value
--> $DIR/borrowck-move-and-move.rs:20:9
|
LL | match Ok(U) {
| ----- move occurs because value has type `std::result::Result<U, U>`, which does not implement the `Copy` trait
LL | a @ Ok(b) | a @ Err(b) => {}
| -------^-
| ^^^^^^^-^
| | |
| | value used here after move
| value moved here
| | value partially moved here
| value used here after partial move
|
= note: partial move occurs because value has type `U`, which does not implement the `Copy` trait
help: borrow this field in the pattern to avoid moving the value
|
LL | a @ Ok(ref b) | a @ Err(b) => {}
| ^^^

error[E0382]: use of moved value
--> $DIR/borrowck-move-and-move.rs:20:29
error[E0382]: use of partially moved value
--> $DIR/borrowck-move-and-move.rs:20:21
|
LL | match Ok(U) {
| ----- move occurs because value has type `std::result::Result<U, U>`, which does not implement the `Copy` trait
LL | a @ Ok(b) | a @ Err(b) => {}
| --------^-
| ^^^^^^^^-^
| | |
| | value used here after move
| value moved here
| | value partially moved here
| value used here after partial move
|
= note: partial move occurs because value has type `U`, which does not implement the `Copy` trait
help: borrow this field in the pattern to avoid moving the value
|
LL | a @ Ok(b) | a @ Err(ref b) => {}
| ^^^

error[E0382]: use of moved value
--> $DIR/borrowck-move-and-move.rs:27:22
error[E0382]: use of partially moved value
--> $DIR/borrowck-move-and-move.rs:27:9
|
LL | match [u(), u(), u(), u()] {
| -------------------- move occurs because value has type `[U; 4]`, which does not implement the `Copy` trait
LL | xs @ [a, .., b] => {}
| -------------^-
| | |
| | value used here after move
| value moved here
| ^^^^^^-^^^^^^^^
| | |
| | value partially moved here
| value used here after partial move
|
= note: partial move occurs because value has type `U`, which does not implement the `Copy` trait

error[E0382]: use of moved value
--> $DIR/borrowck-move-and-move.rs:31:18
error[E0382]: use of partially moved value
--> $DIR/borrowck-move-and-move.rs:31:9
|
LL | match [u(), u(), u(), u()] {
| -------------------- move occurs because value has type `[U; 4]`, which does not implement the `Copy` trait
LL | xs @ [_, ys @ .., _] => {}
| ---------^^^^^^^----
| ^^^^^^^^^-------^^^^
| | |
| | value used here after move
| value moved here
| | value partially moved here
| value used here after partial move
|
= note: partial move occurs because value has type `U`, which does not implement the `Copy` trait

error[E0382]: use of moved value
--> $DIR/borrowck-move-and-move.rs:24:16
--> $DIR/borrowck-move-and-move.rs:24:12
|
LL | fn fun(a @ b: U) {}
| ----^
| ^^^^-
| | |
| | value used here after move
| value moved here
| | value moved here
| value used here after move
| move occurs because value has type `U`, which does not implement the `Copy` trait

error: aborting due to 8 previous errors
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16 changes: 7 additions & 9 deletions src/test/ui/pattern/bindings-after-at/borrowck-pat-at-and-box.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,53 +18,51 @@ fn nc() -> NC {

fn main() {
let a @ box &b = Box::new(&C);
//~^ ERROR use of moved value

let a @ box b = Box::new(C);
//~^ ERROR use of moved value

fn f1(a @ box &b: Box<&C>) {}
//~^ ERROR use of moved value

fn f2(a @ box b: Box<C>) {}
//~^ ERROR use of moved value

match Box::new(C) {
a @ box b => {} //~ ERROR use of moved value
a @ box b => {}
}

let ref a @ box b = Box::new(NC); //~ ERROR cannot move out of value because it is borrowed
//~| ERROR borrow of moved value

let ref a @ box ref mut b = Box::new(nc());
//~^ ERROR cannot borrow value as mutable because it is also borrowed as immutable
let ref a @ box ref mut b = Box::new(NC);
//~^ ERROR cannot borrow value as mutable because it is also borrowed as immutable
let ref a @ box ref mut b = Box::new(NC);
//~^ ERROR cannot borrow value as mutable because it is also borrowed as immutable
//~| ERROR cannot borrow value as immutable because it is also borrowed as mutable
*b = NC;
let ref a @ box ref mut b = Box::new(NC);
//~^ ERROR cannot borrow value as mutable because it is also borrowed as immutable
//~| ERROR cannot borrow value as mutable because it is also borrowed as immutable
//~| ERROR cannot borrow value as immutable because it is also borrowed as mutable
*b = NC;
drop(a);

let ref mut a @ box ref b = Box::new(NC);
//~^ ERROR cannot borrow value as immutable because it is also borrowed as mutable
//~| ERROR cannot borrow value as immutable because it is also borrowed as mutable
//~| ERROR cannot borrow value as mutable because it is also borrowed as immutable
*a = Box::new(NC);
drop(b);

fn f5(ref mut a @ box ref b: Box<NC>) {
//~^ ERROR cannot borrow value as immutable because it is also borrowed as mutable
//~| ERROR cannot borrow value as immutable because it is also borrowed as mutable
//~| ERROR cannot borrow value as mutable because it is also borrowed as immutable
*a = Box::new(NC);
drop(b);
}

match Box::new(nc()) {
ref mut a @ box ref b => {
//~^ ERROR cannot borrow value as immutable because it is also borrowed as mutable
//~| ERROR cannot borrow value as immutable because it is also borrowed as mutable
//~| ERROR cannot borrow value as mutable because it is also borrowed as immutable
*a = Box::new(NC);
drop(b);
}
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