explosive error message

forgotJust

Handler/Posts.hs:45:22:
    Couldn't match type `PostGeneric' with `Maybe'
    Expected type: YesodDB
                     Dtek
                     Dtek
                     (Maybe
                        (Key
                           Database.Persist.GenericSql.Raw.SqlPersist (PostGeneric backend0),
                         Maybe Post))
      Actual type: Database.Persist.GenericSql.Raw.SqlPersist
                     (GGHandler Dtek Dtek IO)
                     (Maybe
                        (Key
                           Database.Persist.GenericSql.Raw.SqlPersist (PostGeneric backend0),
                         PostGeneric backend0))
    In the return type of a call of `selectFirst'
    In the second argument of `($)', namely
      `selectFirst [PostSlug ==. slug] []'

Handler/Posts.hs:45:22:
    Kind incompatibility when matching types:
      backend0 :: (* -> *) -> * -> *
      Post :: *
    Expected type: YesodDB
                     Dtek
                     Dtek
                     (Maybe
                        (Key
                           Database.Persist.GenericSql.Raw.SqlPersist (PostGeneric backend0),
                         Maybe Post))
      Actual type: Database.Persist.GenericSql.Raw.SqlPersist
                     (GGHandler Dtek Dtek IO)
                     (Maybe
                        (Key
                           Database.Persist.GenericSql.Raw.SqlPersist (PostGeneric backend0),
                         PostGeneric backend0))
    In the return type of a call of `selectFirst'
    In the second argument of `($)', namely
      `selectFirst [PostSlug ==. slug] []'
Starting development server...

dist/devel.hs:3:1:
    Failed to load interface for `Application':
      it is not a module in the current program, or in any known package.