Conversions on extension types

[jcouv]

Relates to test plan dotnet/roslyn#66722

[FaustVX]

You have renamed the R extension to EU in the declaration, but not at the usage location :

Suggested change

	implicit extension EU for U
	{
	public static implicit operator EU(int i) => ...;
	}
	implicit extension EInt for int { }
	R r = 42;
	U u = 43;
	EInt ei = 44;
	R r = ei;
	U u = ei;
	implicit extension EU for U
	{
	public static implicit operator EU(int i) => ...;
	}
	implicit extension EInt for int { }
	EU eu = 42;
	U u = 43;
	EInt ei = 44;
	EU eu = ei;
	U u = ei;