Enforced sink argument

[ElegantBeef]

My simple solution would be to emit a hint on the first reuse after a variable 
was supposed to be sinked giving the line info of that sink, this way you can 
disable the hint for if you dont care, or upgrade it to an error in scopes to 
disallow that behavour. It also allows people to clearly see where they're 
sinking but reusing making it easier to optimize if they wish.