The code always lives as AST, and the code that you see in the editor is a pretty-print of the AST. We don't go back and forth between AST and text - when you m

The code always lives as AST, and the code that you see in the editor is a pretty-print of the AST. We don't go back and forth between AST and text - when you make a change in the editor, we look up the "token" where your cursor was, and use it to find the place in the AST that needs a change, and changes only that.