blob: 5a92f8352d2c194be6d369b7788129311612947b (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
|
This error occurs when the compiler is unable to unambiguously infer the
return type of a function or method which is generic on return type, such
as the `collect` method for `Iterator`s.
For example:
```compile_fail,E0284
fn main() {
let n: u32 = 1;
let mut d: u64 = 2;
d = d + n.into();
}
```
Here we have an addition of `d` and `n.into()`. Hence, `n.into()` can return
any type `T` where `u64: Add<T>`. On the other hand, the `into` method can
return any type where `u32: Into<T>`.
The author of this code probably wants `into()` to return a `u64`, but the
compiler can't be sure that there isn't another type `T` where both
`u32: Into<T>` and `u64: Add<T>`.
To resolve this error, use a concrete type for the intermediate expression:
```
fn main() {
let n: u32 = 1;
let mut d: u64 = 2;
let m: u64 = n.into();
d = d + m;
}
```
|
