//! Open document tracking.
//!
//! When the editor opens a file via `textDocument/didOpen`, we mirror its
//! content into the workspace database (so the analyzer sees the buffer, not
//! the disk version). On close we restore from disk if the file existed
//! there, or delete it from the database if it was a virtual / new file.
use FileId;
/// State for a single editor-open document.