Merge: modelize_property: Promote `refine-type` to an error

Signed-off-by: Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>

Pull-Request: #2287
Reviewed-by: Jean Privat <jean@pryen.org>

diff --combined src/modelize/modelize_property.nit
index a313ab6,d0059fe..9465dbb
--- 1/src/modelize/modelize_property.nit
--- 2/src/modelize/modelize_property.nit
+++ b/src/modelize/modelize_property.nit
@@@ -80,6 -80,7 +80,6 @@@ redef class ModelBuilde
        end
  
        # Build the properties of `nclassdef`.
 -      # REQUIRE: all superclasses are built.
        private fun build_properties(nclassdef: AClassdef)
        do
                # Force building recursively
@@@ -1685,8 -1686,7 +1685,7 @@@ redef class ATypePropde
                                break
                        end
                        if p.mclassdef.mclass == mclassdef.mclass then
-                               # Still a warning to pass existing bad code
-                               modelbuilder.warning(n_type, "refine-type", "Redef Error: a virtual type cannot be refined.")
+                               modelbuilder.error(n_type, "Redef Error: a virtual type cannot be refined.")
                                break
                        end
                        if not modelbuilder.check_subtype(n_type, mmodule, anchor, bound, supbound) then