Segfault on trivial consumption of vector

[alexcrichton]

This program will cause a segfault:

fn main() {
  let a : ~[int] = ~[];
  do a.consume |_, _| {}
}

Although if the consumption is changed to vec::consume the segfault does not happen.

This may be a dup of #4318?

[brson]

I've also noticed that the consume method doesn't work. As a workaround, the function, vec::consume does.

[alexcrichton]

Closed by #6903