No error if library exports declaration 'main' which is not a function

[sgrekhov]

According to the recent update of the NNBD specification

Let L be a library that exports a declaration D named main. It is a compile-time error unless D is a function declaration.

But, in fact, there are no errors nor in analyzer nor in CFE in all of the cases below

void getVoid() {}
void main = getVoid();

int get main => 42;

class main {}

typedef void main(List<String> args);

class C {
}
mixin main on C {}

Dart SDK version: 2.10.0-110.0.dev (dev) (Wed Sep 9 17:51:43 2020 -0700) on "windows_x64"

[eernstg]

Created #43556/#43557 specific to CFE/analyzer, moved CFE epic link to #43556.

[franklinyow]

Any work left? Can we close this now?

[eernstg]

No more work here, it's covered by sub-issues and they're closed.