2017-05-27 12:58:52 -05:00
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error[E0597]: `*a` does not live long enough
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2018-12-25 09:56:47 -06:00
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--> $DIR/destructor-restrictions.rs:8:10
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2016-10-26 11:10:39 -05:00
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2023-01-16 20:52:43 -06:00
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LL | let a = Box::new(RefCell::new(4));
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| - binding `a` declared here
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2018-02-22 18:42:32 -06:00
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LL | *a.borrow() + 1
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Use larger span for adjustments on method calls
Currently, we use a relatively 'small' span for THIR
expressions generated by an 'adjustment' (e.g. an autoderef,
autoborrow, unsizing). As a result, if a borrow generated
by an adustment ends up causing a borrowcheck error, for example:
```rust
let mut my_var = String::new();
let my_ref = &my_var
my_var.push('a');
my_ref;
```
then the span for the mutable borrow may end up referring
to only the base expression (e.g. `my_var`), rather than
the method call which triggered the mutable borrow
(e.g. `my_var.push('a')`)
Due to a quirk of the MIR borrowck implementation,
this doesn't always get exposed in migration mode,
but it does in many cases.
This commit makes THIR building consistently use 'larger'
spans for adjustment expressions
The intent of this change it make it clearer to users
when it's the specific way in which a variable is
used (for example, in a method call) that produdes
a borrowcheck error. For example, an error message
claiming that a 'mutable borrow occurs here' might
be confusing if it just points at a usage of a variable
(e.g. `my_var`), when no `&mut` is in sight. Pointing
at the entire expression should help to emphasize
that the method call itself is responsible for
the mutable borrow.
In several cases, this makes the `#![feature(nll)]` diagnostic
output match up exactly with the default (migration mode) output.
As a result, several `.nll.stderr` files end up getting removed
entirely.
2021-09-16 15:01:22 -05:00
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| ^^^^^^^^^^
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2019-04-22 02:40:08 -05:00
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| borrowed value does not live long enough
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| a temporary with access to the borrow is created here ...
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2019-03-09 06:03:44 -06:00
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LL | };
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2020-09-02 02:40:56 -05:00
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| -- ... and the borrow might be used here, when that temporary is dropped and runs the destructor for type `Ref<'_, i32>`
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2016-10-26 11:10:39 -05:00
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| `*a` dropped here while still borrowed
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2019-04-22 02:40:08 -05:00
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2020-04-16 14:43:40 -05:00
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= note: the temporary is part of an expression at the end of a block;
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consider forcing this temporary to be dropped sooner, before the block's local variables are dropped
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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
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LL | let x = *a.borrow() + 1; x
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2021-06-21 21:07:19 -05:00
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| +++++++ +++
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2016-10-26 11:10:39 -05:00
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2017-07-02 05:49:30 -05:00
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error: aborting due to previous error
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2016-10-26 11:10:39 -05:00
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2018-03-03 08:59:40 -06:00
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For more information about this error, try `rustc --explain E0597`.
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