Golang's "named return" is a pretty wild feature I haven't seen elsewhere. (The closest I know is &aux in Common Lisp.)
Implicit `return` example: https://tour.golang.org/basics/7 or even modifying results before returning:
miniblog.
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"Example Driven Development" using Glamorous and Pharo Smalltalk: https://medium.com/feenk/an-example-of-example-driven-development-4dea0d995920
Tests returning values and composing is a really interesting model. It establishes structure and shows which test failure is the most 'fundamental'.
I've just added closure support to my toy programming language: https://github.com/Wilfred/garden/commit/d1fb4566a2187dfe98fb1d2278a7a0d2acd8059e
Closures are more fiddly than I expected, but I now have a much better understanding of what downward/upward funargs are :)
(Downward: passing a closure, upward: returning a closure)
I feel like Rust often pushes me to use concrete types.
It's a lot easier to return a Vec than an impl Iterator. It's not a big problem, but in e.g. Java I'd just say I'm returning some kind of iterator.