C#C
C#•4y ago•
28 replies
Thinker

✅ How to design an error interface

In my current project I have an interface called 
ISymbol
. This interface has tons of derived interfaces (
INamedSymbol
, 
ITypeSymbol
, 
IFunctionSymbol
, 
IVariableSymbol
, among others), which all can have multiple implementations. However, I also have an interface called 
IErrorSymbol
 which just represents an error which has been produced somewhere. There are several cases in which I have to cast between these interfaces, and many times I also have to perform 
is
 checks. The 
IErrorSymbol
 is meant to act as a more or less general-purpose interface which can describe any error, but which also can be used in place of any of the other interfaces.

Currently I have a general 
ErrorSymbol : IErrorSymbol
 implementation, as well as a couple specialized ones like 
NamedErrorSymbol : INamedSymbol, IErrorSymbol
 and 
ErrorTypeSymbol : ITypeSymbol, IErrorSymbol
, although having one of these for every kind of error feels very annoying. What I would love to have is just a single (or at least very few) implementations which can serve the roll of any of the interfaces, however which don't necessarily implicitly implement those interfaces. Does that even make sense? Like, in my ideal world, 
new ErrorSymbol() is ITypeSymbol
 would be false, but 
(ITypeSymbol)new ErrorSymbol()
 would be acceptable. Is there any decent way to describe/implement this?
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