#### §2.3.5.(d) Incompatible redefinition of a role hierarchy

Consider a team `T1` with a method `m` with declared lifting regarding role `R`, where no lifting problems are detected. Consider next a sub-team `T2` which modifies the hierarchy of role `R` such that lifting to `T2.R` is problematic due to a binding ambiguity. In this case clients invoking `T1.m()` could face the situation at runtime that an instance of `T2` is used that unexpectedly fails to lift to its role `R`. Here, the compiler signals a specific error against `T2` alerting of the incompatible change.