Comment by lytigas

According to [1], Crystal Macros "receive AST nodes at compile-time and produce code that is pasted into a program." This is basically the same as Rust procedural macros[2]. You're probably thinking of "Macros by example"[3]

[1] https://crystal-lang.org/reference/syntax_and_semantics/macr...

[2] https://doc.rust-lang.org/reference/procedural-macros.html

[3] https://doc.rust-lang.org/reference/macros-by-example.html