A snapshots data structure provides compilers and other tools with snapshots of a buffer at different points in time. Snapshot heads identify trees within a directed acyclic graph (DAG) of nodes. Leaf nodes of a given tree collectively hold data elements representing information that was resident in the buffer at a particular point in time regardless of subsequent editing of the buffer. During buffer editing operations a new tree is created in the DAG with leaf nodes holding data elements that match one-to-one a subsequence of data elements held by leaf nodes of an existing tree.