No check when a function expects a return value

[yzhang90]

What's your issue about?

Compiler should reject the following program

y: num[3]

@public
def foo(x: num[3]) -> num:
    self.y = x

because foo expects a return value of type num, however the current compiler still compiles.

How can it be fixed?

Need to keep track of the return type of each branch.

Cute Animal Picture

[fubuloubu]

If you don't specify, it probably returns the null case, or 0 for num.

You're correct though, you should have some return statement if your function returns.

[fubuloubu]

This is actually an interesting Formal Verification problem, for methods with lots of branches, is there a branch that does not return a value?

[DavidKnott]

It gets even more fun if we force all branches to end in return or a throw 😄

[fubuloubu]

Well, the easiest way to start is to just throw if no return value is set by end of execution. That solves this scenario easily.

But for future Formal Verification, we would implement a routine to check the program branches all contain a return statement and catch it at compile time instead of during runtime, as the above solution would provide (basically allowing us to remove the throw accounting for this issue)

[jacqueswww]

Closing in favour of #590