As per the discussion during the maintainers meeting, support for matching vectors to corresponding matrix dimensions was dropped due to ambiguous cases with multiple matching dimensions. Instead, only the 1s wild-card style broadcasting will be supported:
array a = randu(5, 3) + randu(5); // Okay
array b = randu(5, 3) + randu(3); // Fails
array c = randu(5, 1, 3) + randu(5); // Okay
array d = randu(5, 1, 3) + randu(1, 4); // Okay
array e = randu(5, 1, 3) + randu(1, 1, 3); // Okay
array f = randu(5, 1, 3) + randu(5, 5, 3); // Okay
array g = randu(5, 1, 3) + randu(5, 3, 3); // Okay
array i = randu(3, 255, 255) + randu(3); // Okay