Declare a method that always throws an exception?

Question

I have a method like:

int f() {   try {     int i = process();     return i;   } catch(Exception ex) {     ThrowSpecificFault(ex);   } } 

This produces a compiler error, "not all code paths return a value". But in my case ThrowSpecificFault() will always throw (the appropriate) exception. So I am forced to a put a return value at the end but this is ugly.

The purpose of this pattern in the first place is because "process()" is a call to an external web service but need to translate a variety of different exceptions to match a client's expected interface (~facade pattern I suppose).

Any cleaner way to do this?

Answer 1

I suggest that you convert ThrowSpecificFault(ex) to throw SpecificFault(ex); the SpecificFault method would return the exception object to be thrown rather than throwing it itself. Much cleaner.

This is the pattern recommended by Microsoft's guidelines.

Answer 2

Right now a return type can be a type, or "void" meaning "no return type". We could in theory add a second special return type "never", which has the semantics you want. The end point of an expression statement consisting of a call to a "never" returning method would be considered unreachable, and so it would be legal in every context in C# in which a "goto", "throw" or "return" is legal.

It is highly unlikely that this will be added to the type system now, ten years in. Next time you design a type system from scratch, remember to include a "never" type.