Erroneous "Not all code paths return a value" when using `return invalid` for early exits

[addison-adler]

• When writing code in the 'Early return' style/pattern and using return invalid, linter flags an error "not all code paths return a value"
  • This happens because there is not another return invalid at the end of the function.
  • Given that return invalid is the default return value (whether specified or not), I'm wondering/hoping if this lint rule can be updated to accommodate the early exit pattern without requiring us to add return invalid at the end of all our functions
• Note: if you use this pattern with a sub function definition instead of function, the linter does not throw any warnings/errors
  • I prefer to write these kind of early-exit functions using sub, but in projects with named-function-style: "no-sub" that isn't possible

Link to the linter code/line that throws this warning/error

Example of early-return pattern:

' early-exit pattern using 'sub'
' passes lint
' this will NOT throw "not all code paths return a value"
sub myFunc (arg)
  if arg = invalid then return

  ' do something with arg
  ' this function does not return anything
end function

' early-exit pattern using 'function'
' fails lint
' this will throw "not all code paths return a value"
function myFunc (arg)
  if arg = invalid then return invalid

  ' do something with arg
  ' this function does not return anything (it is equivalent to a sub call definition)
end function

' early-exit pattern using 'function' with extra return
' passes lint
function myFunc (arg)
  if arg = invalid then return invalid

  ' do something with arg
  ' this function does not return anything (it is equivalent to a sub call definition)
  
  return invalid ' adding superfluous 'return invalid' makes lint happy
end function

If I can find the time and the bslint devs are open to changes to support this, I will try to submit a PR if I can get the time to do so