Macro _field_with_key

macro_rules! _field_with_key {
    (
      $key : ident,
      $src : expr,
      $how : ty,
      $fallback1 : ty,
      $fallback2 : ty
      $(,)?
    ) => { ... };
}

Macro to create a field with a key and formatted value.

This macro helps to convert a field of a structure into one or another string representation depending on the parameters how, fallback1, and fallback2. Unlike _field_with_key, the key is the path of the expression and is deduced from the last part of the expression. For example, for this.is.field, the key is field.