https://issues.dlang.org/show_bug.cgi?id=14835
--- Comment #4 from Steven Schveighoffer <[email protected]> --- What the compiler is doing here is giving you information that code you wrote will not get executed. The problem is that the code in question is only one *particular* execution (or instantiation) of that code. To your example, isEven!1 will execute the line of code that is deemed to be unreachable. The issue here is that the compiler can't "try all possibilities" to see if it will be able to find a path to that code (halting problem). So probably we should turn off that feature when the code has taken a branch based on a template constant or a static if. The compiler should assume the other branch could be executed for a different instantiation, and so not complain for this one. I don't think there's a "right" way to handle this. The error in question is truly a function of optimization and folding, but the user sees things in terms of lines of code. To say a line of code may not be executed if you call it one way is an error, even though it will be executed if you call it another way, doesn't make a lot of sense. If we are going to be "helpful", we should at least be accurate. This is coming from someone who doesn't know how the compiler is implemented, or doesn't even know how compilers are implemented. So perhaps this is too difficult a task? BTW, I was also saying that you *could* fix the problem without dummy variables or recursion, but I agree that the compiler is being unhelpful here. --
