Detect struct construction with private field in field with default
When trying to construct a struct that has a public field of a private type, suggest using `..` if that field has a default value.
```
error[E0603]: struct `Priv1` is private
--> $DIR/non-exhaustive-ctor-2.rs:19:39
|
LL | let _ = S { field: (), field1: m::Priv1 {} };
| ------ ^^^^^ private struct
| |
| while setting this field
|
note: the struct `Priv1` is defined here
--> $DIR/non-exhaustive-ctor-2.rs:14:4
|
LL | struct Priv1 {}
| ^^^^^^^^^^^^
help: the type `Priv1` of field `field1` is private, but you can construct the default value defined for it in `S` using `..` in the struct initializer expression
|
LL | let _ = S { field: (), .. };
| ~~
```