Multi-line ternary doesn't work

[BSteffaniak]

e.g.

public Int days =>
    start == null || end == null ?
        -1 :
        (end.millis - start.millis) / DateTime.SECS_DAY

but this does:

public Int days =>
    start == null || end == null ? -1 : (end.millis - start.millis) / DateTime.SECS_DAY