Compiling code like

    namespace Lib {
        public class Useful : Object {
            public string info {internal set; get;}
        }
    }

with the --vapi switch results in something like 

    namespace Lib {
        public class Useful : Object {
            public Useful ();
            public string info { get; internal get; }
        }
    }

written to the vapi file.

I wasn't sure if this was a bug or not, so I asked in #vala on GimpNet, and nemequ instructed me to open this ticket:

    04:50:05 <~nemequ> yeah, file a bug, please.  if nothing else we should warn there instead of silently ignoring the programmer's intentions :/

It seems as though https://bugzilla.gnome.org/show_bug.cgi?id=653909 might be related.