Cannot open source file " literally any zephyr file"

[Kylobyte25]

I'm pulling my hair out here. 

Why would syntax errors completely break the toolchain?

Every now and then ill have a syntax error which causes the build to fail, the entire application corrupts and key files are then lost. 

In this state a prestine build does not work. 
undoing my changes does not work. 

Deleting the application does not work. 

Even clearing out everything, starting with a new hello world example and sterile nrf52840dk development kit build fails and key includes fail to be found.

Why would this happen?

currently no zephyr file can be found. 
I've reinstalled the toolchain. 

Previously I've had to completley uninstall vscode and reinstall nrfconnect and all the extensions. 

This is a NIGHTMARE. what is going on.

[Kylobyte25]

so far, I've learned

1) prestine builds do pretty much nothing unless you completely delete the build folder.  whats the point of a pristine build then? what does clean build do if both of these options do nothing?  why is all guidance missing this key detail?  

2) improper alias in the device tree can completely corrupt your files.  This is kind of infuriating and there's no error code that points me to this as the culprit. 

3)really upset that you can waste days of work just trying to understand why vscode and nrfconnect operate the way they do. 

no explications as to why standard examples and devkit builds get corrupted also. not exactly sure how this can be possible.