Right tree rotation

For old root $y$ with left child $x$ and untouched subtrees $A,B,C$, change the shape from $((A,x,B),y,C)$ to $(A,x,(B,y,C))$. Both have inorder sequence $A,x,B,y,C$. In a destructive traversal that only rotates at the current root, this transformation extends the right spine by one node and decreases the left-size potential by one.