Constructor injection for complex types

[ajcvickers]

That is, bind an instance of a nested complex type to a constructor parameter.

Related to #12078

[bbartels]

Out of curiosity, would this be a reasonable ticket to pick up for a community contribution? Am I correct in assuming that this wouldn't really be touching query pipeline logic? Would be interesting in giving this a shot if not deemed complex enough to only be done by more seasoned EF contributors.
Not had too deep of a look yet, but presumably most of the changes would be happening here?

efcore/src/EFCore/Metadata/Internal/ConstructorBindingFactory.cs

Line 251 in 2ecd08f

private bool TryBindConstructor<T>(

[roji]

/cc @AndriySvyryd. Also given we're doing a big push on complex types and given the number of votes, we may want to try to get this in for 10.

[AndriySvyryd]

I'm not very familiar with this code, but you would also need to modify https://github.com/dotnet/efcore/blob/main/src/EFCore/Metadata/Internal/PropertyParameterBindingFactory.cs and https://github.com/dotnet/efcore/blob/main/src/EFCore/Query/Internal/EntityMaterializerSource.cs#L77

It would be significantly more complex to enable this for collections of complex types or complex properties mapped to JSON, so perhaps it's best to tackle those separately.