• 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: Windows 10
• Poetry version: 1.1.4
• Link of a Gist with the contents of your pyproject.toml file:

Issue

With the linked pyproject.toml file, running

poetry export -f requirements.txt --output requirements.txt --without-hashes

generates this requirements.txt file.

These lines cause dependency conflict on Python 3.7 when installing this requirements file with pip.

ipython==7.16.1; python_version < "3.7" or python_version >= "4.0" or python_version >= "3.6" and implementation_name == "cpython"
ipython==7.20.0; python_version >= "3.7" and python_version < "4.0"

It tries to install both 7.16.1 (because python_version >= "3.6" and implementation_name == "cpython" matches) and 7.20.0 (because python_version >= "3.7" and python_version < "4.0" matches).