model: in case of error, methods of MVirtualType return a bottomtype

Signed-off-by: Jean Privat <jean@pryen.org>

diff --git a/src/model/model.nit b/src/model/model.nit
index 851efda..ccb7522 100644 (file)
--- a/src/model/model.nit
+++ b/src/model/model.nit
@@ -1010,7 +1010,7 @@ abstract class MType
        # The result is returned exactly as declared in the "type" property (verbatim).
        # So it could be another formal type.
        #
-       # In case of conflict, the method aborts.
+       # In case of conflicts or inconsistencies in the model, the method returns a `MBottomType`.
        fun lookup_bound(mmodule: MModule, resolved_receiver: MType): MType do return self
 
        # Resolve the formal type to its simplest equivalent form.
@@ -1024,6 +1024,8 @@ abstract class MType
        #
        # By default, return self.
        # See the redefinitions for specific behavior in each kind of type.
+       #
+       # In case of conflicts or inconsistencies in the model, the method returns a `MBottomType`.
        fun lookup_fixed(mmodule: MModule, resolved_receiver: MType): MType do return self
 
        # Can the type be resolved?
@@ -1365,7 +1367,7 @@ class MVirtualType
 
        redef fun lookup_bound(mmodule: MModule, resolved_receiver: MType): MType
        do
-               return lookup_single_definition(mmodule, resolved_receiver).bound.as(not null)
+               return lookup_single_definition(mmodule, resolved_receiver).bound or else new MBottomType(model)
        end
 
        private fun lookup_single_definition(mmodule: MModule, resolved_receiver: MType): MVirtualTypeDef
@@ -1400,7 +1402,8 @@ class MVirtualType
                assert resolved_receiver isa MClassType # It is the only remaining type
 
                var prop = lookup_single_definition(mmodule, resolved_receiver)
-               var res = prop.bound.as(not null)
+               var res = prop.bound
+               if res == null then return new MBottomType(model)
 
                # Recursively lookup the fixed result
                res = res.lookup_fixed(mmodule, resolved_receiver)