Dart is an open-source, scalable programming language, with robust libraries and runtimes, for building web, server, and mobile apps.
On Wed Nov 28, we will disable support for the old getter definition syntax. The empty formal parameter list in the getter definition will be a compile error.
To convert your sources from old to new syntax, simply remove the empty parameter list after the getter name, for example:
old: int get Length() => a.length;
new: int get Length => a.length;