improvement: delete old compilation units from pc

[kasiaMarek]

The idea is to delete compilation units from presentation compiler, that are no longer needed. The heuristic is as follows, we keep compilation units for the following paths:

• last 5 focused - probably we want this to be a configurable number
• modified since the last compilation
• outlined

I'm also hoping this means we can delete uncached pc.

[filipwiech]

last 5 focused

How will it work in editors which do not support custom Metals didFocus LSP extension? Would it track last 5 didOpen calls instead? :slightly_smiling_face:

[kasiaMarek]

How will it work in editors which do not support custom Metals didFocus LSP extension? Would it track last 5 didOpen calls instead? 🙂

"Focus" is called here on:

• didOpen
• didChange (if didFocus is not supported)
• didFocus
• didClose (will focus on the previous opened)

[kasiaMarek]

I changed this to use last N files for which compilation unit was requested instead of last N focused. It's both easier (no need for additional pc method) and should be more reliable.