Comment (by Roland Haas):

My take would be that to me:

IO::out_dir =

would be an error but that:

IO::out_dir = ""

is valid (so not the RHS is emtpy but the value). The tricky bit would seem to classify:

foo = 
bar = 12

as an error on foo, while allowing:

foo = 
bar
baz = 12

‌

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2533/activethorns-not-accepted-in-parameter