Actually, what could really helpful would be a "simple" precond-postcond-invariant calculator...
The principle is quite simple: for every method you write, the "calculator" tells you what "outside" variable are modified. Obviously it seems quite simple with FP... but not so simple with object/imperative language as soon as you start to call other procedures or subsystems or syscall!
Of course, it could be nice that this "calculator" works inline (while you write your code) and not afterwards (when the program is compiled). It should be "smart enough" for example to tell you that your code is calling an INSERT on a database in a sub-sub-sub procedure of your code or that it is effectively calling some file writing somewhere in the called path
The principle is quite simple: for every method you write, the "calculator" tells you what "outside" variable are modified. Obviously it seems quite simple with FP... but not so simple with object/imperative language as soon as you start to call other procedures or subsystems or syscall!
Of course, it could be nice that this "calculator" works inline (while you write your code) and not afterwards (when the program is compiled). It should be "smart enough" for example to tell you that your code is calling an INSERT on a database in a sub-sub-sub procedure of your code or that it is effectively calling some file writing somewhere in the called path