Work in Progress

We are still in the process of writing the documentation for Scala 3. You can help us to improve the documentation.

Are you searching for the Scala 2 documentation?

Macros in Scala 3

Tutorial

Language

This tutorial covers all the features involved in writing macros in Scala 3.

The metaprogramming API of Scala 3 is designed in layers to gradually support different levels of use-cases. Each successive layer exposes additional abstractions and offers more fine-grained control.

  • As a starting point, the new inline feature allows some abstractions (values and methods) to be marked as statically reducible. It provides the entry point for macros and other metaprogramming utilities.

  • Compile-time operations offer additional metaprogramming utilities that can be used within inline methods (for example to improve error reporting), without having to define a macro.

  • Starting from inline methods, macros are programs that explicitly operate on programs.

    • Macros can be defined in terms of a high-level API of quoted expressions, that admits simple construction and deconstruction of programs expressions.

    • Macros can also be defined in terms of a more low-level API of Reflection, that allows detailed inspection of programs.

The tutorial uses the API of Scala 3.0.0-RC3. The API had many small changes in this revision.

🚧 We are still in the process of writing the tutorial. You can help us 🚧

Contributors to this page: