since per the Nim Manual source files are in the UTF-8 encoding, it's probably
safe to assume that string literals are UTF-8
https://nim-lang.org/docs/manual.html#lexical-analysis-encoding
> All Nim source files are in the UTF-8 encoding (or its ASCII subset). Other
encodings are not supported.

but the bytes in a Nim string don't actually assume any particular encoding:
https://nim-lang.org/docs/manual.html#types-string-type
> Per convention, all strings are UTF-8 strings, but this is not enforced. For
example, when reading strings from binary files, they are merely a sequence of
bytes.

just something to be aware of when working with arbitrary data coming from
files, network, etc.