Continue to label that is not for a loop

Is this valid code?
```dart
int findOverlap(List list, List sublist) {
for (int i = 0; i < list.length; ++i) {
outer:
{
for (int j = 0; j < sublist.length && i + j < list.length; ++j) {
if (list[i + j] != sublist[j]) continue outer;
}
return i;
}
}
return list.length;
}
```
Here, `outer` labels the block, not `for (int i`. So, according to `18.15 Continue` in the specification, `continue outer;` should be a compile-time error? But this code runs :-)

And the analyzer also does not report it as an error.
And I suspect that it might do something unexpected for flow analysis as well, possibly because of how the analyzer drives it.

https://github.com/dart-lang/sdk/blob/578b602deca0790f4e2bf25acaaa9571ed17192c/pkg/vm/lib/transformations/type_flow/utils.dart#L322-L330

Start with section 18.15, “Continue,” in the Dart specification and compare its rule for labeled statements with the behavior shown in the issue. Inspect the referenced type-flow code in pkg/vm/lib/transformations/type_flow/utils.dart around lines 322-330, then reproduce the example and check analyzer diagnostics. Done means the implementation and analyzer consistently handle continue-to-block labels according to the specification.

Written by the indexing model from the issue text.