This extension is in alpha and will probably have many bugs.
It's goal is to be a fast IDE that is performant on large projects and doesn't consume too much memory.
If you have a small or medium sized project you will probably be better off using https://github.com/nwolverson/vscode-ide-purescript.
To use this project you will have to install a fork of the purs compiler with LSP support. This can be installed at https://www.npmjs.com/package/@oxfordabstracts/purescript-lsp.
After installing the fork, you should delete the output and rebuild your project to index your project.
TODO
Purescript with lsp binary. https://www.npmjs.com/package/@oxfordabstracts/purescript-lsp
TODO