[Proposal] allow is operator compare generic type

[leandromoh]

as well we can do x is string to check if the instance x is of type string, would be amazing extend this behaviour to generic types, like T is string.

T is SomeType would be equivalent to typeof(T).IsAssignableTo(SomeType)

[jnm2]

@leandromoh Why would it be amazing to be able to do T is string rather than typeof(T) == typeof(string)?

[YairHalberstadt]

Note these are not equivalent. T is SomeType would be equivalent to typeof(T).IsAssignableTo(SomeType).

[leandromoh]

@YairHalberstadt yes, you are right about what the proposal means. I will fix the summary

@jnm2 it would avoid boilerplate code (like use typeof twice).

[jnm2]

@YairHalberstadt @leandromoh IsAssignableTo is in API review, hasn't been shipped: dotnet/runtime#30714

@leandromoh I was going to disagree that typeof twice is enough boilerplate to blink at, but now that I assume it's going to be updated to IsAssignableFrom which is an API that I can't stand, I actually think you have a point. However, I don't often see IsAssignableFrom in code. Do you?

[leandromoh]

I actually think you have a point. However, I don't often see IsAssignableFrom in code. Do you?

@jnm2 Yes, when dealing with generics and metaprogramming (like a lot of libraries does) comparing types is a common task. so should be nice to simplify theses cases:

1. from typeof(T).IsAssignableTo(SomeType) to T is SomeType

2. from typeof(T) == SomeType to T == SomeType