llogiq
commented
6 years ago We should perhaps stress the third point more – that the cost of requiring #[derive(Debug)] is acceptable in exchange for a safe default (not having it in the first place).
Incidentally, this argument also applies to auto-deriving Default. The code bloat argument is weaker there, because the method is smaller, can likely be constified and inlined.
Asked on Reddit at least two times:
@llogiq's answer is a good start; https://www.reddit.com/r/rust/comments/8677z1/why_does_rust_not_derivedebug_by_default/dw378lk/
Not sure where this should go to. Maybe under the "Debugging and Tooling" section.