When using Lombok it will use a compiler plugin for this so maven builds have @nonnull generated as if-statements. I dont know if intellij uses their own plugin but they do support Lombok in maven projects, so maybe thats where this is coming from. Afaik intellij has no built in compiler but relies on java .
I was initially impressed with Lombok and then ran into all the downsides of it and it was institutionally abandoned at one particular firm I was with (100s of devs).
