Dart should support `&&=` and `||=` operators.

[lrhn]

Dart does not currently support using the && and || operators in assignments.
It allows other non-short-circuiting binary operators, and it allows ??=, which is short-circuiting.
Users have expressed surprise that those two are not supported.

This is a solution to #23.

See https://dart-review.googlesource.com/c/sdk/+/43500/ for a specification.

[har79]

Dupe of #23?

[kevmoo]

Indeed a dupe of #23 – CC @mit-mit and @eernstg

[mit-mit]

Not really; #23 is a "language request" (aka a "problem"), the present bug is a "language feature" i.e. a possible solution to the former request/problem. For more details, see https://github.com/dart-lang/language/blob/master/doc/life_of_a_language_feature.md

I have clarified this in the top-comment.

[kevmoo]

@mit-mit Noticed the labels, too.