"fall-through" and default values

[giuliano]

I've bumped into the following subtlety and was wondering if anyone could help 
me clarify it. Why does the following fails to compile:
    
    
    proc aProc*(): int =
      try:
        1
      except Exception as exc:
        echo "oops"
    
    # Fails with "Error: expression '1' is of type 'int' and has to be used (or 
discarded)"
    
    
    Run

but this doesn't:
    
    
    proc aProc*(): int =
      try:
        return 1
      except Exception as exc:
        echo "oops"
    # prints 1
    
    
    Run

and neither does this?
    
    
    proc aProc*(): int =
      try:
        1
      except Exception as exc:
        2
    # prints 1
    
    
    Run