tree 934ff3499e098a1bac9d71a2f94005a07697183b
parent e416b4b0568e0778bee0bb98b142e82e3a377e23
author Nate Bosch <nbosch@google.com> 1604963792 -0800
committer Nate Bosch <nbosch@google.com> 1604963792 -0800

Different pattern for _span so it doesn't need to be late

Instead of marking the field nullable, or late, add a constructor in the
abstract class and use it from the others.

It was already impossible to correctly subclass `YamlNode` from outside
the library, so the addition of a private constructor should not be
breaking.