New static analysis of `main`

[eernstg]

The PR dart-lang/language#1146 introduces a new section in the null-safety specification about the static requirements on the main function. That section will replace the section Scripts in the language specification when null safety is in a stable release, so a comparison between the 'Scripts' section in the language specification and the new section in the null-safety specification may be helpful. We need tests for this new behavior.

[sgrekhov]

@eernstg are there implementation issues for the new static analysis of main?

[sgrekhov]

@eernstg, is the following an error?

library main;
...

And the second one

import "some_lib.dart" as main;
...

[eernstg]

implementation issues

No, the change was supposed to make the spec track the implementations more closely, not the other way around.

library main;

That is not an error, a libraryName does not introduce its name into any scope.

import "some_lib.dart" as main;

That is also allowed: When main is an import prefix it is not exported. It is only an exported main which is subject to restrictions.

[sgrekhov]

import "some_lib.dart" as main;

That is also allowed: When main is an import prefix it is not exported. It is only an exported main which is subject to restrictions.

@eernstg, in this case we'll have an error if library has main() function

import "some_lib.dart" as main;
main() { // error - The name 'main' is already used as an import prefix and can't be used to name a top-level element.
}

Is this expected?