Nested with expressions

[AFatNiBBa]

Example

Let's assume we have these two structs

public struct Example1
{
    public int Value1;
    public Example2 Inner;

    public Example1() => Inner = new() { Value4 = 4 };
}

public struct Example2
{
    public int Value2;
    public int Value3;
    public int Value4;
}

It is possible for me to initialize Example1 like this

var a = new Example1
{
    Value1 = 1,
    Inner = { Value2 = 2, Value3 = 3 }
};

But if I write a with expression, I won't be able to MODIFY Example1.Inner

var b = a with
{
    Value1 = 4,
    Inner = { Value2 = 5, Value3 = 6 } // Unallowed!
};

I assume this is because if Example2 were to be a class, that would have changed the original Example2 instance stored in a.Inner

Proposal

I think that it would be beneficial for nested sets of { } inside a with expression to be converted in additional with expressions like so

var b = a with
{
    Value1 = 4,
    Inner = a.Inner with { Value2 = 5, Value3 = 6 }
};

This would allow the modification only for clonable objects (record, struct) and wouldn't work on standard reference types

[colejohnson66]

#8289