Zero[].
Succ[prev].
Succ[prev]. //Duplicate record
Add[left; right].
Add[lhs; Rhs[]]. //Declaration with value property. Duplicate record

Zero[1]: 0; //Wrong number of arguments
Succ[x]: Add[\x; 1]; //Value with declaration property. Unbound output
Add[\left; \right]: Subtract[Neg[\left]; Neg[\right]]; //Undeclared records