Implicit line continuations

WARNING: This is a speculative post. Caveat emptor.

One of the things that we’d like to address in the next version is line continuations. We know that they tend to annoy many developers who want to break their logical lines across multiple physical lines, and we’ve gotten many requests to get rid of them altogether. Unfortunately, there’s a reason we haven’t just dropped them–they actually are needed in certain scenarios. For example, take the following contrived example:

    Sub Main()
    End _

If I remove the line continuation, I’ll now get a compile error because “End” now is the “End” statement, and the Sub looks like it’s trying to start a new subroutine in the middle of the current subroutine. There are quite a few of these syntactic ambiguities sprinkled throughout our grammar, some of which might be quite obscure and unnoticed until someone’s code actually broke. So instead of taking a maximalist approach and trying to remove the line continuation everywhere, we’ve been thinking about a more minimalist approach and looking at where removing the line continuation might be most useful. This produced a much more tractable list of places where we might productively remove the line continuation. In particular:

  1. After binary operators in expression contexts. Note that this does not include assignment operators. For example:
    a = b +
  2. After the following punctuators: comma (“,”), open parenthesis (“(“), open curly brace (“{“), begin embedded expression in XML (“<%=”). For example:
        "{0} {1}",
  3. Before the following punctuators: close parenthesis (“)”), close curly brace (“}”), end embedded expression in XML (“%>”). For example:
        "{0} {1}",
  4. After an open angle bracket (“<“) in an attribute context, before a close angle bracket (“>”) in an attribute context, and after a close angle bracket in a non-file-level attribute context (i.e. an attribute that does not specify “Assembly” or “Module”). For example:
        Sub Main()
        End Sub
  5. Before and after query expression operators. For example:
    Dim ys = From x In xs
             Where x > 5
                ten = x * 10,
                twenty = x * 20,
                thirty = x * 30

One thing that is not currently on the list is allowing an implicit line continuation after a dot, so you couldn’t break up “a.b.c” implicitly. It’s not that we can’t do dot, just that it’s quite a bit more expensive and problematic for Intellisense. We’d be interested to hear if this is something people really want to/need to do, or if it’s just a nice-to-have.

Are there any other places that we missed that you can think of?

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