Fix for use_primary_constructors produces syntax error when there's no constructor

[stereotype441]

In a project that's using language version 3.13, if the use_primary_constructors lint is enabled, the lint fires for a class like this:

class C<T> {}

(Which is admittedly kind of silly, since there's no value to be added by converting to primary constructor syntax when there's no constructor present).

If you bring up the context menu and select "Convert the default constructor to a primary constructor", the code is changed to:

class C()<T> {}

This is incorrect. It should be:

class C<T>() {}

Not sure how high of a priority this is, because we (currently) don't have plans to heavily advertise this lint.

[bwilkerson]

I believe that this was fixed by https://dart-review.git.corp.google.com/c/sdk/+/506760. Please reopen the issue and let me know if you still see the problem after moving to a build that includes that fix.

Which is admittedly kind of silly ...

True, but were targeting a maximal conversion, and it seemed appropriate in that context. :-)

[stereotype441]

I'm on d6889ba, which includes that fix, and I'm still seeing the problem.

Note that https://dart-review.git.corp.google.com/c/sdk/+/506760 fixes

class C<T> {
  C();
}

I can verify that this is indeed fixed.

Whereas the problem I'm seeing is with:

class C<T> {}

So it looks like the fix wasn't general enough.