With quant.info listing quant:quant_api as a dependency and quant_api listing quant:quant as a dependency then you have a circular dependency that makes it so you can't uninstall either module:
Kristens-MacBook-Pro:quantcdn kristenpol$ ddev drush pm:list |grep quant
Quant Quant (quant) Module Enabled
Quant Quant API (quant_api) Module Enabled
Quant Quant Cron (quant_cron) Module Not installed
Quant Quant File (quant_file) Module Not installed
Quant Quant Redirects (quant_redirect) Module Not installed
Quant Quant scheduler (quant_scheduler) Module Not installed
Quant Quant sitemap (quant_sitemap) Module Not installed
Kristens-MacBook-Pro:quantcdn kristenpol$ ddev drush pm:disable quant
The following extensions will be disabled: quant, quant_api
Do you really want to continue? (y/n): y
quant was disabled successfully. [ok]
quant_api was disabled successfully. [ok]
Kristens-MacBook-Pro:quantcdn kristenpol$ ddev drush pm:uninstall quant
To uninstall quant, the following modules must be uninstalled first: quant_api, quant [error]
There were no modules that could be uninstalled. [ok]
Kristens-MacBook-Pro:quantcdn kristenpol$ ddev drush pm:uninstall quant_api
To uninstall quant_api, the following modules must be uninstalled first: quant_api, quant [error]
There were no modules that could be uninstalled. [ok]
Kristens-MacBook-Pro:quantcdn kristenpol$ ddev drush pm:uninstall quant_api quant
To uninstall quant_api, the following modules must be uninstalled first: quant_api, quant [error]
To uninstall quant, the following modules must be uninstalled first: quant_api, quant [error]
There were no modules that could be uninstalled.
Update quant_api to not have quant as a dependency in the info file yet still require that it's installed since it uses things like the quant_help helper function.
Fixed
1.0
Code
Merged in GitHub. This will be synced to d.o as part of the next release:
📌 Create Quant release 7.x-1.3 Fixed