The code is somewhat invasive, but it seems hard to do this in a
clean way, since the design itself involves a bunch of 'action
at a distance'.
Issue #1819
The last argument of the call must be a block, and the type of this
argument must a function returning bool. `break` and `cont` are
supported in the body of the block, and return `false` or `true` from
the function. When the end of the function is reached, `true` is
implicitly returned.
for vec::all([1, 2, 3]) {|elt|
if elt == 2 { break; }
log(error, elt);
}
Issue #1619
