Provide hint when cast needs a dereference
For a given code:
``` rust
vec![0.0].iter().map(|s| s as i16).collect::<Vec<i16>>();
```
display:
``` nocode
error: casting `&f64` as `i16` is invalid
--> file3.rs:2:35
|
2 | vec![0.0].iter().map(|s| s as i16).collect::<Vec<i16>>();
| - ^^^
| |
| did you mean `*s`?
```
instead of:
``` nocode
error: casting `&f64` as `i16` is invalid
--> <anon>:2:30
|
2 | vec![0.0].iter().map(|s| s as i16).collect();
| ^^^^^^^^
|
= help: cast through a raw pointer first
```
Fixes #37338.