What is a non-method-local var in Scala?
scala
Solution
A method local variable is a local variable declared in the scope of a method.
Consequently a non-method-local variable ought to be a variable with a wider scope, such as class scope.
Can't tell for sure why one would say that they are problematic. Perhaps it is simply due to the fact that they introduce a mutable state in objects.
Problem
In the comments to Scala Sink or Swim Josh Sureth calls out non-method-local vars as a cause of problems in Scala code. That page is the only Google hit for the phrase `non-method-local vars`, so what does it mean, and what is the problem?