Question

Formulated in another way:

could you give an example assignment of JAVA, x=y, such that the declared type of "x" is not a supertype of that of "y"?

Recall that the declared type is "T" if x is declared as "T x". (supertype includes "the same type" by convention.)

Answer 1

In assignment the LHS must be the type or the RHS or a super type.
With supertype also covariant array types are meant: String[] to Object[] (never use that!).
Or widening (primitive types) may take place: assigning an int to a float.
Or boxing may happen: Integer to int, int to Integer.