Better error message for dealing with bad constructors

config/models

Test
   field Text.

Error:

Model.hs:13:7:
    Illegal type constructor or class name: ‘Text.’

and it goes on with a huge dump of TH splices.

In practice, it's unlikely any user will actually face this unless they accidentally typo, but it's good practice to give good error messages.

The fix is as follows:
In persistent, Database.Persist.Quasi, Lines 67-69,

    getCon t =
        case T.breakOnEnd "." t of
            (_, "") -> FTTypeCon Nothing t

should be

    getCon t =
        case T.breakOnEnd "." t of
            (t', "") -> error ("Invalid data constructor - dangling qualifier: " ++ T.unpack t')

Since this is harmless, maybe it can be snuck in a code refactor commit in the future?

Run the reproducer in config/models and inspect Database.Persist.Quasi around lines 67-69; Model.hs:13:7 shows the current compiler error and TH dump. Done means dangling-qualified constructors produce the specified invalid-data-constructor message instead of the existing error output.