Error message for mutating field of immutable struct could be clearer #27593
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A-diagnostics
Area: Messages for errors, warnings, and lints
Comments
steveklabnik
added
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A-diagnostics
|
Triage: no change. I agree that "immutable field" is bad here. |
|
Probably needs an extension of #39139 to immutable bindings instead of just references. Unfamiliar with the code, but possibly easy? |
steveklabnik
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frewsxcv
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Mar 18, 2017
…rner
Point to let when modifying field of immutable variable
Point at the immutable local variable when trying to modify one of its
fields.
Given a file:
```rust
struct Foo {
pub v: Vec<String>
}
fn main() {
let f = Foo { v: Vec::new() };
f.v.push("cat".to_string());
}
```
present the following output:
```
error: cannot borrow immutable field `f.v` as mutable
--> file.rs:7:13
|
6 | let f = Foo { v: Vec::new() };
| - this should be `mut`
7 | f.v.push("cat".to_string());
| ^^^
error: aborting due to previous error
```
Fix rust-lang#27593.
arielb1
pushed a commit
to arielb1/rust
that referenced
this issue
Mar 18, 2017
…rner
Point to let when modifying field of immutable variable
Point at the immutable local variable when trying to modify one of its
fields.
Given a file:
```rust
struct Foo {
pub v: Vec<String>
}
fn main() {
let f = Foo { v: Vec::new() };
f.v.push("cat".to_string());
}
```
present the following output:
```
error: cannot borrow immutable field `f.v` as mutable
--> file.rs:7:13
|
6 | let f = Foo { v: Vec::new() };
| - this should be `mut`
7 | f.v.push("cat".to_string());
| ^^^
error: aborting due to previous error
```
Fix rust-lang#27593.
arielb1
pushed a commit
to arielb1/rust
that referenced
this issue
Mar 19, 2017
…rner
Point to let when modifying field of immutable variable
Point at the immutable local variable when trying to modify one of its
fields.
Given a file:
```rust
struct Foo {
pub v: Vec<String>
}
fn main() {
let f = Foo { v: Vec::new() };
f.v.push("cat".to_string());
}
```
present the following output:
```
error: cannot borrow immutable field `f.v` as mutable
--> file.rs:7:13
|
6 | let f = Foo { v: Vec::new() };
| - this should be `mut`
7 | f.v.push("cat".to_string());
| ^^^
error: aborting due to previous error
```
Fix rust-lang#27593.
frewsxcv
added a commit
to frewsxcv/rust
that referenced
this issue
Mar 19, 2017
…rner
Point to let when modifying field of immutable variable
Point at the immutable local variable when trying to modify one of its
fields.
Given a file:
```rust
struct Foo {
pub v: Vec<String>
}
fn main() {
let f = Foo { v: Vec::new() };
f.v.push("cat".to_string());
}
```
present the following output:
```
error: cannot borrow immutable field `f.v` as mutable
--> file.rs:7:13
|
6 | let f = Foo { v: Vec::new() };
| - this should be `mut`
7 | f.v.push("cat".to_string());
| ^^^
error: aborting due to previous error
```
Fix rust-lang#27593.
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The above code gives this compile error:
From my perspective, this implies that the field somehow needs to be marked as mutable, when in fact the user error is that the struct is immutable.
I believe the error message could be improved by saying something like
cannot borrow fieldvof immutable structfas mutable.#18150 is "related".
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