Provide more context when mutably borrowing an imutably borrowed value #148508
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Point at statics and consts being mutable borrowed or written to:
```
error[E0594]: cannot assign to immutable static item `NUM`
--> $DIR/E0594.rs:4:5
|
LL | static NUM: i32 = 18;
| --------------- this `static` cannot be written to
...
LL | NUM = 20;
| ^^^^^^^^ cannot assign
```
Point at the expression that couldn't be mutably borrowed from a pattern:
```
error[E0596]: cannot borrow data in a `&` reference as mutable
--> $DIR/mut-pattern-of-immutable-borrow.rs:19:14
|
LL | match &arg.field {
| ---------- this cannot be borrowed as mutable
LL | Some(ref mut s) => s.push('a'),
| ^^^^^^^^^ cannot borrow as mutable
```
|
This PR modifies |
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added
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|
r? @nnethercote rustbot has assigned @nnethercote. Use |
| { | ||
| err.span_label( | ||
| local.source_info.span, | ||
| format!("this cannot be {acted_on}"), |
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This does not seem to have a testcase.
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It's covered by a few for Boring like in tests/ui/nll/dont-print-desugared.stderr, and tests/ui/pattern/mut-pattern-of-immutable-borrow.rs covers the BlockTailTemp case.
| | | ||
| LL | *input = self.0; | ||
| | ^^^^^^^^^^^^^^^ `input` is a `&` reference, so the data it refers to cannot be written | ||
| | ^^^^^^^^^^^^^^^ `input` is a `&` reference, so the data it refers to cannot be written to |
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I don't think this is grammatical. I'd expect either "the reference cannot be written to", or "the data cannot be written"; "to" does not work without indirection.
Perhaps rephrase with "input is a & reference, so *input cannot be written to"?
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good catch. changed.
4 participants
Point at statics and consts being mutable borrowed or written to:
Point at the expression that couldn't be mutably borrowed from a pattern:
Partially address #74617.