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Suggest ; or assignment to drop borrows in tail exprs

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Address the diagnostics part of #70844.

```
error[E0597]: `counter` does not live long enough
  --> $DIR/issue-54556-niconii.rs:22:20
   |
LL |     if let Ok(_) = counter.lock() { }
   |                    ^^^^^^^-------
   |                    |
   |                    borrowed value does not live long enough
   |                    a temporary with access to the borrow is created here ...
...
LL | }
   | -
   | |
   | `counter` dropped here while still borrowed
   | ... and the borrow might be used here, when that temporary is dropped and runs the destructor for type `std::result::Result<MutexGuard<'_>, ()>`
   |
help: consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped
   |
LL |     if let Ok(_) = counter.lock() { };
   |                                      ^
```
This commit is contained in:
Esteban Küber 2020-04-16 12:43:40 -07:00
parent 8ce3f840ae
commit 2c6094e5d0
12 changed files with 117 additions and 36 deletions
Download patch file Download diff file Expand all files Collapse all files

5
src/test/ui/nll/issue-54382-use-span-of-tail-of-block.stderr
View file

@ -13,7 +13,10 @@ LL |
LL | ;
| - ... and the borrow might be used here, when that temporary is dropped and runs the `Drop` code for type `D`
|
= note: The temporary is part of an expression at the end of a block. Consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped.
help: consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped
|
LL | D("other").next(&_thing1);
| ^
error: aborting due to previous error

5
src/test/ui/nll/issue-54556-niconii.stderr
View file

@ -13,7 +13,10 @@ LL | }
| `counter` dropped here while still borrowed
| ... and the borrow might be used here, when that temporary is dropped and runs the destructor for type `std::result::Result<MutexGuard<'_>, ()>`
|
= note: The temporary is part of an expression at the end of a block. Consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped.
help: consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped
|
LL | if let Ok(_) = counter.lock() { };
| ^
error: aborting due to previous error

7
src/test/ui/nll/issue-54556-stephaneyfx.stderr
View file

@ -12,7 +12,12 @@ LL | }
| `stmt` dropped here while still borrowed
| ... and the borrow might be used here, when that temporary is dropped and runs the destructor for type `std::iter::Map<Rows<'_>, [closure@$DIR/issue-54556-stephaneyfx.rs:28:14: 28:23]>`
|
= note: The temporary is part of an expression at the end of a block. Consider forcing this temporary to be dropped sooner, before the block's local variables are dropped. For example, you could save the expression's value in a new local variable `x` and then make `x` be the expression at the end of the block.
= note: the temporary is part of an expression at the end of a block;
consider forcing this temporary to be dropped sooner, before the block's local variables are dropped
help: for example, you could save the expression's value in a new local variable `x` and then make `x` be the expression at the end of the block
|
LL | let x = rows.map(|row| row).next(); x
| ^^^^^^^ ^^^
error: aborting due to previous error

5
src/test/ui/nll/issue-54556-temps-in-tail-diagnostic.stderr
View file

@ -12,7 +12,10 @@ LL |
LL | ;
| - ... and the borrow might be used here, when that temporary is dropped and runs the `Drop` code for type `D`
|
= note: The temporary is part of an expression at the end of a block. Consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped.
help: consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped
|
LL | D(&_thing1).end();
| ^
error: aborting due to previous error

51
src/test/ui/nll/issue-54556-used-vs-unused-tails.stderr
View file

@ -8,7 +8,10 @@ LL | { let mut _t1 = D(Box::new("t1")); D(&_t1).end() } ; //
| | borrowed value does not live long enough
| a temporary with access to the borrow is created here ...
|
= note: The temporary is part of an expression at the end of a block. Consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped.
help: consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped
|
LL | { let mut _t1 = D(Box::new("t1")); D(&_t1).end(); } ; // suggest `;`
| ^
error[E0597]: `_t1` does not live long enough
--> $DIR/issue-54556-used-vs-unused-tails.rs:13:55
@ -20,7 +23,10 @@ LL | { { let mut _t1 = D(Box::new("t1")); D(&_t1).end() } } ; //
| | borrowed value does not live long enough
| a temporary with access to the borrow is created here ...
|
= note: The temporary is part of an expression at the end of a block. Consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped.
help: consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped
|
LL | { { let mut _t1 = D(Box::new("t1")); D(&_t1).end(); } } ; // suggest `;`
| ^
error[E0597]: `_t1` does not live long enough
--> $DIR/issue-54556-used-vs-unused-tails.rs:16:55
@ -32,7 +38,10 @@ LL | { { let mut _t1 = D(Box::new("t1")); D(&_t1).end() }; } //
| | borrowed value does not live long enough
| a temporary with access to the borrow is created here ...
|
= note: The temporary is part of an expression at the end of a block. Consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped.
help: consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped
|
LL | { { let mut _t1 = D(Box::new("t1")); D(&_t1).end(); }; } // suggest `;`
| ^
error[E0597]: `_t1` does not live long enough
--> $DIR/issue-54556-used-vs-unused-tails.rs:19:55
@ -44,7 +53,10 @@ LL | let _ = { let mut _t1 = D(Box::new("t1")); D(&_t1).end() } ; //
| | borrowed value does not live long enough
| a temporary with access to the borrow is created here ...
|
= note: The temporary is part of an expression at the end of a block. Consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped.
help: consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped
|
LL | let _ = { let mut _t1 = D(Box::new("t1")); D(&_t1).end(); } ; // suggest `;`
| ^
error[E0597]: `_t1` does not live long enough
--> $DIR/issue-54556-used-vs-unused-tails.rs:22:55
@ -56,7 +68,10 @@ LL | let _u = { let mut _t1 = D(Box::new("t1")); D(&_t1).unit() } ; //
| | borrowed value does not live long enough
| a temporary with access to the borrow is created here ...
|
= note: The temporary is part of an expression at the end of a block. Consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped.
help: consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped
|
LL | let _u = { let mut _t1 = D(Box::new("t1")); D(&_t1).unit(); } ; // suggest `;`
| ^
error[E0597]: `_t1` does not live long enough
--> $DIR/issue-54556-used-vs-unused-tails.rs:25:55
@ -68,7 +83,12 @@ LL | let _x = { let mut _t1 = D(Box::new("t1")); D(&_t1).end() } ; //
| | borrowed value does not live long enough
| a temporary with access to the borrow is created here ...
|
= note: The temporary is part of an expression at the end of a block. Consider forcing this temporary to be dropped sooner, before the block's local variables are dropped. For example, you could save the expression's value in a new local variable `x` and then make `x` be the expression at the end of the block.
= note: the temporary is part of an expression at the end of a block;
consider forcing this temporary to be dropped sooner, before the block's local variables are dropped
help: for example, you could save the expression's value in a new local variable `x` and then make `x` be the expression at the end of the block
|
LL | let _x = { let mut _t1 = D(Box::new("t1")); let x = D(&_t1).end(); x } ; // `let x = ...; x`
| ^^^^^^^ ^^^
error[E0597]: `_t1` does not live long enough
--> $DIR/issue-54556-used-vs-unused-tails.rs:30:55
@ -80,7 +100,12 @@ LL | _y = { let mut _t1 = D(Box::new("t1")); D(&_t1).end() } ; // `l
| | borrowed value does not live long enough
| a temporary with access to the borrow is created here ...
|
= note: The temporary is part of an expression at the end of a block. Consider forcing this temporary to be dropped sooner, before the block's local variables are dropped. For example, you could save the expression's value in a new local variable `x` and then make `x` be the expression at the end of the block.
= note: the temporary is part of an expression at the end of a block;
consider forcing this temporary to be dropped sooner, before the block's local variables are dropped
help: for example, you could save the expression's value in a new local variable `x` and then make `x` be the expression at the end of the block
|
LL | _y = { let mut _t1 = D(Box::new("t1")); let x = D(&_t1).end(); x } ; // `let x = ...; x`
| ^^^^^^^ ^^^
error[E0597]: `_t1` does not live long enough
--> $DIR/issue-54556-used-vs-unused-tails.rs:37:55
@ -93,7 +118,10 @@ LL | fn f_local_ref() { let mut _t1 = D(Box::new("t1")); D(&_t1).unit() } //
| | borrowed value does not live long enough
| a temporary with access to the borrow is created here ...
|
= note: The temporary is part of an expression at the end of a block. Consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped.
help: consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped
|
LL | fn f_local_ref() { let mut _t1 = D(Box::new("t1")); D(&_t1).unit(); } // suggest `;`
| ^
error[E0597]: `_t1` does not live long enough
--> $DIR/issue-54556-used-vs-unused-tails.rs:40:55
@ -106,7 +134,12 @@ LL | fn f() -> String { let mut _t1 = D(Box::new("t1")); D(&_t1).end() } //
| | borrowed value does not live long enough
| a temporary with access to the borrow is created here ...
|
= note: The temporary is part of an expression at the end of a block. Consider forcing this temporary to be dropped sooner, before the block's local variables are dropped. For example, you could save the expression's value in a new local variable `x` and then make `x` be the expression at the end of the block.
= note: the temporary is part of an expression at the end of a block;
consider forcing this temporary to be dropped sooner, before the block's local variables are dropped
help: for example, you could save the expression's value in a new local variable `x` and then make `x` be the expression at the end of the block
|
LL | fn f() -> String { let mut _t1 = D(Box::new("t1")); let x = D(&_t1).end(); x } // `let x = ...; x`
| ^^^^^^^ ^^^
error: aborting due to 9 previous errors

7
src/test/ui/span/destructor-restrictions.stderr
View file

@ -11,7 +11,12 @@ LL | };
| |
| `*a` dropped here while still borrowed
|
= note: The temporary is part of an expression at the end of a block. Consider forcing this temporary to be dropped sooner, before the block's local variables are dropped. For example, you could save the expression's value in a new local variable `x` and then make `x` be the expression at the end of the block.
= note: the temporary is part of an expression at the end of a block;
consider forcing this temporary to be dropped sooner, before the block's local variables are dropped
help: for example, you could save the expression's value in a new local variable `x` and then make `x` be the expression at the end of the block
|
LL | let x = *a.borrow() + 1; x
| ^^^^^^^ ^^^
error: aborting due to previous error

14
src/test/ui/span/issue-23338-locals-die-before-temps-of-body.stderr
View file

@ -12,7 +12,12 @@ LL | }
| `y` dropped here while still borrowed
| ... and the borrow might be used here, when that temporary is dropped and runs the destructor for type `std::cell::Ref<'_, std::string::String>`
|
= note: The temporary is part of an expression at the end of a block. Consider forcing this temporary to be dropped sooner, before the block's local variables are dropped. For example, you could save the expression's value in a new local variable `x` and then make `x` be the expression at the end of the block.
= note: the temporary is part of an expression at the end of a block;
consider forcing this temporary to be dropped sooner, before the block's local variables are dropped
help: for example, you could save the expression's value in a new local variable `x` and then make `x` be the expression at the end of the block
|
LL | let x = y.borrow().clone(); x
| ^^^^^^^ ^^^
error[E0597]: `y` does not live long enough
--> $DIR/issue-23338-locals-die-before-temps-of-body.rs:17:9
@ -27,7 +32,12 @@ LL | };
| |
| `y` dropped here while still borrowed
|
= note: The temporary is part of an expression at the end of a block. Consider forcing this temporary to be dropped sooner, before the block's local variables are dropped. For example, you could save the expression's value in a new local variable `x` and then make `x` be the expression at the end of the block.
= note: the temporary is part of an expression at the end of a block;
consider forcing this temporary to be dropped sooner, before the block's local variables are dropped
help: for example, you could save the expression's value in a new local variable `x` and then make `x` be the expression at the end of the block
|
LL | let x = y.borrow().clone(); x
| ^^^^^^^ ^^^
error: aborting due to 2 previous errors