No. So far, only Microsoft has implemented the language spec and as long as no one else does it, no one can. Prove to me that "anyone can implement it" by pointing to someone who has done it, instead of relying on some theoretical "it could be done" fantasy.
The amount of effort, time, energy needed is just not something anybody else outside of MS is able or willing to put into implementing the language spec.
https://en.m.wikipedia.org/wiki/List_of_compilers#C%23_compi...
At least 3 serious, large scale long term non-Microsoft implementations.
Or something like https://github.com/SandipKumar05/C-sharp-Compiler and then you can argue that if it only implements a tiny part of the spec it doesn’t count and that proves it’s a Microsoft conspiracy?
Visual C# is Microsoft.
Visual C# Express is Microsoft.
Mono -> Xamarin is now Microsoft.
Portable.NET -> Dot Gnu Project, has been decommissioned 11 years ago.
SharpDevelop -> IC#Code Team, project will be/has already been decommissioned, see [0].
Roslyn -> .NET Foundation, which was written by Microsoft, and is currently maintained (according to [1]) primarily by people working at Microsoft.
That last repo you posted is of course nice but like you said, it's tiny, doesn't even support arrays and is undocumented. Seems more like a assignment for a compiler building course. Like it though.
So, thanks for making me do some googling on this, but it just proved my point.
[0] https://github.com/icsharpcode/SharpDevelop/issues/799#issue...
Yes I am sure that it takes a lot of time, but anyone who is willing and able can do it there is no-one stopping anyone from doing it.
The spec is open, the source code for pretty much everything is now open and is sitting on github, it has been ported to MacOS, iOS and Linux and it runs on both x86 and ARM what more do you people want?