[tialaramex]

println! is only a declarative macro, whereas Maud is a proc macro.

The declarative macros aren't too head-twisting for tools, they just expand as declared, this can sometimes have a few surprising effects but generally it is very manageable. Procedural macros have essentially unlimited power and thus are sometimes entirely impossible to analyse.

[pornel]

println! depends on a proc macro: https://doc.rust-lang.org/stable/src/core/macros/mod.rs.html...

[tialaramex]

I see a built-in there. Are you really seeing a proc macro?