[Proposal] Allow defining local aliases for types

[VBAndCs]

I came across this code:

public List<Expression<Func<T, object>>> Includes { get; } = new List<Expression<Func<T, object>>>();

And I wondered: Can't I simplify this to:

using Expr = Expression<Func<T, object>>

public List<Expr> Includes { get; } = new List< Expr>();

This seems readable.
But unfortunately it is not possible, since T exists only inside the class scope, and using exists only in file/namespace scope!

So, I wish if C# allows using type aliases inside classes. This is a must in today's projects that contain very complex generics and lambdas that make our heads spin.

[Joe4evr]

Duplicate of #2488, #1170, #410 and #259.

[VBAndCs]

Seems a popular demand :)

[VBAndCs]

Too many votes for those proposals, yet none is a champion!

[theunrepentantgeek]

Development of C# isn't a democracy - votes on issues merely show what's popular, not what's good.

The LDM decides on what goes into the next version of the language - and they take into account a far wider range of inputs than just this repo.

Someone pointed out (I think it was @CyrusNajmabadi, but I'm not 100% sure) that the feedback in this repo is less than the statistical noise in feedback through other channels. Fortunately, the LDM takes a special interest in what's said here because many of the contributors take the time to carefully think through issues instead of just banging on their own drum.

[YairHalberstadt]

Closing as duplicate between #2488, #1170, #410 and #259.