• I am on the latest Poetry version.
• I have searched the issues of this repo and believe that this is not a duplicate.
• If an exception occurs when executing a command, I executed it again in debug mode (-vvv option).

• OS version and name: any
• Poetry version: current master of poetry-core
• Link of a Gist with the contents of your pyproject.toml file: not applicable

Issue

When calling set_constraint() on a Dependency object, the _pretty_constraint attribute is not changed. This leads to an inconsistent state of the Dependency object. Because pretty_constraint is used in base_pep_508_name and therefore indirectly in __str__, this issue probably can result in incorrect constraints being printed resp. written to a file.