Dafny VS extension crashes when including lengthy files

[parno]

If you include a file that's longer than the including file, the Dafny extension will often crash. Here's a small example. Create two files:

includer.dfy:

include "includee.dfy"

method test()

and includee.dfy:

function TestFunc(x:int) : int
{
    x + 2
}

lemma SomeProperties(y:int)
    ensures TestFunc(y) > y;
{

}

This will crash the extension. The problem is that the code that tries to add "Go to definition" functionality doesn't check whether the expression it's trying to tag is in the current buffer/file. In this case, it sees TestFunc in the ensures to SomeProperties, and tries to add a tag to the current snapshot, which fails with an out of range error.