Breaking change: compile-time error for `continue` statement having invalid target

[asashour]

Change

A compile-time error will be triggered for continue statement targeting invalid labeled statements (which are not for, do, while, or switch case).

Original issue is #49852, see also dart-lang/language#2586

Note: there is already continue_label_on_switch, which would be part of the new error.

Rationale

As per 18.15 of the specs, it is a compile-time error for the continue label to target non-loops or switch members.

Impact

There is a chance that some invalid usage is encountered.

Mitigation

Users have to change the code and properly target valid labeled statements.

[asashour]

https://dart-review.googlesource.com/c/sdk/+/279343

As the relevant CL has landed, the proposed CL adds CHANGELOG and closes this issue.

I hope that follows the breaking-changes process.

[itsjustkevin]

@vsmenon @grouma @Hixie @eernstg could you take a look at this? It has been merged for a month now.

[eernstg]

This is a bug fix that eliminates a soundness issue. The update in https://dart-review.googlesource.com/c/sdk/+/279343 was a new entry in CHANGELOG.md, which means that it (presumably) hasn't been implemented, but I doubt that there is any other way ahead than implementing it.

@vsmenon, @grouma, @Hixie, do you see a reason to reject this request?

[vsmenon]

lgtm - thanks!

@eernstg - is this a change in the spec or enforcement of existing spec?

[eernstg]

Enforcement of existing spec.

[asashour]

The change has been implemented in 49c7d93

[grouma]

LGTM