analyzer should warn when using Set literals with SDK < 2.2.0

[kevmoo]

Just like we did for Future without dart:async imports, we should warn package authors if they are using a feature outside of their defined SDK constraint.

VERY helpful to avoid publishing packages that silently break folks.

CC @mit-mit @devoncarew @stereotype441

[devoncarew]

Are checks like these things we should roll into pub publish itself?

[kevmoo]

Are checks like these things we should roll into pub publish itself?

Likely, although it should be done server-side. The problem: it'll make publish slow. CC @mit-mit

Either way, having it analyzer itself is a good first step.

[kevmoo]

FYI: marked this P1 because I think it's critical to help our users "do the right thing"

[bwilkerson]

Is this something we're going to want for every experiment that gets enabled? (I think the answer it "yes", but wanted to confirm.)

If so, we should make sure that it's part of the analyzer's implementation plan from now on.

Is this going to hold up shipping 2.2.0? (I think that's the implication of the P1 and milestone, but again wanted to confirm.)

[kevmoo]

Is this something we're going to want for every experiment that gets enabled? (I think the answer it "yes", but wanted to confirm.)

If so, we should make sure that it's part of the analyzer's implementation plan from now on.

I think so! As language features are introduced, it'd be amazing if we could warn people about this.

(I'd love to do it for APIs, too.)

sdk/sdk/lib/internal/internal.dart

Lines 200 to 204 in edca616

	@Since("2.2")
	class Since {
	final String version;
	const Since(this.version);
	}

Is this going to hold up shipping 2.2.0? (I think that's the implication of the P1 and milestone, but again wanted to confirm.)

I'd like it to block 2.2.0 – later and the ship has sailed. We should talk to @dgrove and @mit-mit about that

[devoncarew]

Given the amount of moving parts between landing a change in the sdk repo, and it making it's way into even a dev sdk, I suspect we've already missed 2.2.0. We should likely plan for a change landing in a .x patch release, and design the feature we'd ultimately like to see land.

[kevmoo]

okay...would be good to track.

[bwilkerson]

https://dart-review.googlesource.com/c/sdk/+/96837

[kevmoo]

Closed in 5fdb3c5

[kevmoo]

Reverted in 0f4a208

[stereotype441]

Fix was re-landed in 495c319