X can be

• a class instance (for static or non-static fields)
• or an array (for indexed element or subrange assignment)
• or a classname, or a class(_,_) or array(_) type (for static fields)
• but not a String (no fields to retrieve)

Fspec can be

• an atomic field name (overloading through shadowing has yet to be handled properly)
• or an array index I (X must be an array object: V is assigned to X[I])
• or a pair I-J of integers (X must be an array object, V must be a list of values: successive members of V are assigned to X[I..J])

V must be a suitable value or object.