Allow using URI strings in "part of" declarations

[davidmorgan]

According to the 1.23 CHANGELOG this is now supported in the language, but dartfmt doesn't seem to be happy with it.

dartfmt 0.2.16 on the command line removes a "part of" URI from the file if I use one.

Formatting via the dart_style library seems to refuse to format files using a URI "part of" -- seen in this pull request for source_gen trying to change the generated code: dart-lang/source_gen#138

[davidmorgan]

Do we just need to wait for an analyzer release to fix this? Thanks.

[munificent]

No, there's work to be done in dartfmt too.

It was a mistake to put this feature in the 1.23 CHANGELOG and has since been removed: dart-lang/sdk@9add06f. The feature hasn't officially shipped yet (in part because dartfmt doesn't support it yet).

[davidmorgan]

Got it. Thanks!