This document summarizes Hamlet D'Arcy's presentation on AST transformations using tools like Lombok, Groovy, CodeNarc, and Mirah. It discusses how these tools allow manipulating abstract syntax trees to add functionality like automatic property generation, static analysis, and embedded domain-specific languages. Local AST transformations are performed without changing bytecode or requiring new semantics. Type checking can also be added through transformations. Mirah compiles to pure Java classes without additional syntax.