[API Proposal]: Create fullnameof(element) expression

[DrkWzrd]

Background and motivation

We have an excellent timesaving and error avoidance expression called nameof(ElementToGetName) so useful in so many cases.

In some other cases (usually logging-related events, debugging, even some errors validations) developers need the full name of a class with the namespace or the full name of a member with the class name.

The first thing require a hard-coded string (which you'll have to update every time you rename the class or the namespace, or even if you modify the hierarchy of namespaces) or a smelly typeof(Class).FullName which has a performance penalty if called so many times.
And the second thing requires a concatenation of nameof(Class)+"."+nameof(Member).

API Proposal

An expression like said:

fullnameof(ElementToGetName)

API Usage

// A example class
namespace Store.Shelf.Box { class Potato { int Quality {get;} } }
// A example call;
var box_fullName = fullnameof(Box); //It returns "Store.Shelf.Box"
var potato_fullName = fullnameof(Potato); //It returns "Store.Shelf.Box.Potato"
var quality_fullName = fullnameof(Potato.Quality); //It returns "Potato.Quality", right now nameof(Potato.Quality) returns "Quality"

Risks

At first sight, no one i can see.

[yaakov-h]

This is quite similar to and a partial duplicate of #701.

[jnm2]

I'm proposing making typeof(...).FullName a constant, which will help with some of these use cases: #8505

It would be great to hear in that thread about real-world use cases that support doing this, as well as real-world use cases for fullnameof that aren't addressed by that proposal and don't have a good solution today.