Macrodetail

Macrodetail is a concept used in metaprogramming and macro systems to describe the granularity and fidelity of information produced by macro expansion. It refers to the amount and type of detail that a macro’s expansion yields, including the generated code, the original arguments, source location metadata, and related annotations or hygiene information.

In practice, macrodetail encompasses several components. The generated output may include or omit wrappers, comments, and metadata that map the expansion back to its source. Argument binding, type information, and source spans can be preserved to aid debugging and tooling. Hygiene artifacts and dependency notes may also be attached to expanded code to help maintainability and avoid naming conflicts across expansions.

Different languages handle macrodetail in distinct ways. In Lisp and other homoiconic macro systems, macros operate on code as data, providing rich opportunities to control or inspect detail. In Rust, procedural macros can emit tokens with spans that improve error messages and debugging traces, effectively shaping macrodetail. In C and C++, preprocessor macros expand text with minimal structural information, often limiting macrodetail and complicating debugging. The level of detail exposed or preserved influences tooling, error reporting, and reproducibility of builds.

Applications of macrodetail include debugging, code generation, and documentation of macro behavior. A balance is sought between providing enough detail for tracing and keeping the macro surface area small to avoid code bloat and complexity. Proper management of macrodetail supports clearer error messages, better maintainability, and more predictable compilation.