During compile parsing happens in two stages:
1. diet parse (any blocks like method bodies are skipped)
2. parse bodies
Both phases did read the source .java file from file system. With this
change the file contents is kept in CompilationResult.contentRef until
no longer needed. It is cached in
a SoftReference to avoid OutOfMemoryError.

https://github.com/eclipse-jdt/eclipse.jdt.core/issues/2691