C# Language Proposal discussion: Target-typed static member lookup

[lihaoyi]

There’s been some discussion around adopting Swift-like .member shorthand syntax in Scala, to avoid having to use the full Object.member syntax based on target-typing. As another data point, apart from Swift, C# seems like it might be getting this in the near future:

• Proposal discussion: Target-typed static member lookup · dotnet/csharplang · Discussion #9078 · GitHub

[soronpo]

Why not continue on that thread?

Relative scoping for hierarchical ADT arguments

I also wish to add a use-case that wasn’t discussed here thus far (and didn’t exist for me when I initiated the idea several years ago). I call it “by type” argument assignment (instead of by order or by name), and it’s using opaque types + givens + implicit conversion to do something which I think is cool. What I do is that I have a configuration context object where each value gets its own unique type import wvlet.log.LogLevel //using an external logger library import CompilerOptions.* //im…

[lihaoyi]

Because I couldnt find it haha, if any mods could help consolidate this thread into the other one that would be great

[mberndt]

I actually made a similar proposal not long ago where I proposed to use a placeholder for the companion object (I suggested # at the time to avoid clashes with existing syntax, but the specific syntax isn’t important to me), with scoping rules analogous to those that we use for _ placeholders in lambda expressions. Then you could just write #.member. But it’s more powerful than a simple .member syntax because it can be used also in situations where you don’t want to access a member. For example, you could write something like

def fun(ints: Vector[Int]) = ???

val ints = List(1,2,3)
fun(ints.to(#)) // compiler figures out which collection type to convert to

Unfortunately Martin didn’t like it, saying it’s too prone to misuse for unreadable code.