Parser: recover on missing types in decls

[auduchinok]

Adds recovery for missing types in declarations:

typeR={ F:}

typeR={ F }

typeU=| A ofi:

typeT=valx:

typeT()=inherit

typeT()=interface

typeT()=member valP:=1

It also disallows interface declaration members to be at the same indentation when the new indentation rules are enabled:

typeI=interfaceabstractP:intend

and requires at least one additional space:

typeI=interfaceabstractP:intend

It's needed for recovery of unfinished interface members:

typeT()=interface// unfinishedmemberthis.P=1// was incorrectly parsed as an interface member

[edgarfgp]

Would it make sense to include the following scenario here too?

[auduchinok]

Would it make sense to include the following scenario here too?

Yes, but it's unrelated to this PR. 🙂

[auduchinok]

The most of the changes have been proposed via separate PRs. We can close this one now 🎉