block
    statement (assignment)
      expression
        operator (post-increment)
          operator (dereference)
            variable
      expression
        variable

Or perhaps I am wrong and it would generate an AST like you describe and rely on later passes to actually create a proper dependency graph. My mental model of how these kinds of postfix operators work always assumed it must very early on turn it into two separate statements. Thank you for the suggestions.

Oops, you're right - I got the operators the wrong way around! I forget the precise precedence of * and ++ in C sometimes. Assuming that it would be bracketed as *(lwr++), it should actually be:

  block
    statement (assignment)
      expression
        operator (dereference)
          operator (post-increment)
            variable
      expression
        variable