Go's %v leaves a lot to be desired, even when using %+#v to print even more info. I wish there was a format string to deeply traverse into pointers. Currently I have to import go-spew for that, which is a huge annoyance.

Python does it best from what I've seen so far, with its __repr__ method.

The default %v does leave some to be desired, but don't underestimate the utility of being able to shove anything at it and get something back. This is especially important because this applies recursively; you can have a structure that may have something "unprintable" buried deeply in it, but at least it won't prevent you from printing everything else.

Strongly-typed languages that do not force any sort of stringification on values, and thus refuse to compile if you try to dump a simple log message of one of these values out, are really annoying to work with. I understand the conceptual purity of saying "Hey, maybe not everything even has a string representation" but it makes debugging a real pain. If I were writing a new language today I think I'd mandate that everything gets a default debugging string output by default because the alternative is just so rough.

Even a not-great printer that may have a sort of "*unprintable*" bailout, or print something not terribly useful, but doesn't actually stop you from printing anything, is better than a language that completely rejects it at compile time.

Go has both Stringer and GoStringer interfaces, which is basically the same thing as __repr__.