use-all (C121)
This rule is turned on by default.
What it does
Checks whether use statements are used correctly.
Why is this bad?
When using a module, it is recommended to add an 'only' clause to specify which components you intend to use:
Example
! Not recommended
use, intrinsic :: iso_fortran_env
! Better
use, intrinsic :: iso_fortran_env, only: int32, real64
This makes it easier for programmers to understand where the symbols in your code have come from, and avoids introducing many unneeded components to your local scope.