+ # A VT is fixed when:
+ # * the VT is (re-)defined with the annotation `is fixed`
+ # * the VT is (indirectly) bound to an enum class (see `enum_kind`) since there is no subtype possible
+ # * the receiver is an enum class since there is no subtype possible
+ redef fun lookup_fixed(mmodule: MModule, resolved_receiver: MType): MType
+ do
+ assert not resolved_receiver.need_anchor
+ resolved_receiver = resolved_receiver.as_notnullable
+ 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)
+
+ # Recursively lookup the fixed result
+ res = res.lookup_fixed(mmodule, resolved_receiver)
+
+ # 1. For a fixed VT, return the resolved bound
+ if prop.is_fixed then return res
+
+ # 2. For a enum boud, return the bound
+ if res isa MClassType and res.mclass.kind == enum_kind then return res
+
+ # 3. for a enum receiver return the bound
+ if resolved_receiver.mclass.kind == enum_kind then return res
+
+ return self
+ end
+