Fix raw identifiers usage in Display/Debug derives (#431)

[tyranron]

Resolves #431

Synopsis

See #431 (comment):

Both of the following generate a working impl:

#[derive(Display)]
#[display("{thing}")]
struct Struct<T> {
    thing: T,  // generic
}

#[derive(Display)]
#[display("{thing}")]
struct Struct {
    r#thing: i32,  // raw
}

but this generates an impl that does not compile.

#[derive(Display)]
#[display("{thing}")]
struct Struct<T> {
    r#thing: T,  // raw, generic
}

error[E0277]: `T` doesn't implement `derive_more::Display`
 --> src/main.rs:3:10
  |
3 | #[derive(Display)]
  |          ^^^^^^^ `T` cannot be formatted with the default formatter
  |
  = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
  = note: required for `&T` to implement `derive_more::Display`
  = note: this error originates in the derive macro `Display` (in Nightly builds, run with -Z macro-backtrace for more info)
help: consider restricting type parameter `T` with trait `Display`
  |
5 | struct Struct<T: derive_more::Display> {
  |                ++++++++++++++++++++++

Solution

Consider field with raw identifiers correctly in transparency checks and dereferencing.

Checklist

• Documentation is updated (not required)
• Tests are added/updated
• CHANGELOG entry is added

[tyranron]

ping @JelteF

[tyranron]

@JelteF done!