[notduncansmith]

Perhaps the author was inspired by the Go language, as those are both Go-isms: Go's only loop is a for loop, and := tells the compiler to infer the variable type when initializing.

In fact, this snippet is only a few deviations away from being valid Go code.

[AYBABTME]

Their compiler is written in Go.

See https://github.com/ark-lang/ark

[warmwaffles]

You also need to remember that at one point Go's compiler was written in C, as with rust. It's all apart of the language evolution.

[AYBABTME]

I'm not blaming them, just saying there's evidence the authors are quite familiar with Go. =P

[michaelmior]

:= isn't really stating to infer the type (although this happens) but a way to differentiate variable initialization with assignment. When using := the variable is created while = is just a regular assignment. Having these as separate operators prevents errors like this:

    foo := 3
    fooo = 4

The second line is invalid because fooo does not exist.

[fapjacks]

Indeed it is written in Go, after all.