The final else block is a good point. In R this would cause an error during the attempt to return a non-existent variable (so at least R doesn't form a new var

The final else block is a good point. In R this would cause an error during the attempt to return a non-existent variable (so at least R doesn't form a new variable on reference, just on assignment). This better is you now can see the error if it occurs. But it isn't everything as you may see this first in production (if you have insufficient testing). I still like the bug to not be at all possible. For example in Java we could declare the variable final at the top of the block and then the compiler would only accept code where the variable is assigned exactly once on all code paths (no matter how unlikely the path). This would catch a bunch of other popular errors (like forgetting to type "else" before one of the chained "if"s (as "else if" is unfortunately just a convention).