The use clause follows the name clause. It may be empty or of the form
'use' M1 , ... , Mnwhere M1 , ... , Mn is a list of module names (optionally separated by commas). The items provided by modules that appear in this list can be used in the module containing the use clause.
For example. if module IR provides a definition of a type Expr and module CodeGen contains a use clause
'use' IR, TargetFilethen the type Expr can be used inside CodeGen.
A module with an empty use clause cannot use items declared in other modules.