Treat '...' like missing() in AST

[hcirellu]

This should fix #275.

I added a special handling for symbol ... in [.integer64.

The example in the related issue is added to the tests.

Closes #275

[MichaelChirico]

another test case I had in mind is a helper passing ... something like

getter = function(x, ...) x[...]

calling that directly and with lapply should work

[hcirellu]

another test case I had in mind is a helper passing ... something like

getter = function(x, ...) x[...]

calling that directly and with lapply should work

This works now:

getter = function(x, ...) x[...]
getter(integer64())
# integer64(0)
getter(integer64(), "sss")
# integer64(0)
lapply(integer64(), getter)
# list()
lapply(integer64(1), getter)
# [[1]]
# integer64
# [1] 0
lapply(integer(), getter)
# list()
lapply(integer(1), getter)
# [[1]]
# [1] 0

[MichaelChirico]

Great! Let's add it to the test suite

[MichaelChirico]

Thanks!