Nomenclature question: what is the EXPR in for PATTERN in EXPR { } called?

[jieyouxu]

Location

https://doc.rust-lang.org/reference/expressions/loop-expr.html#iterator-loops

Context

I was reviewing a test cleanup PR rust-lang/rust#141974, and I was trying to say something about the EXPR in

for PATTERN in EXPR {
    //         ^--- what is this expr called?
    // ...
}

but I couldn't find a good term for this¹². The current grammar calls this EXPR

Expression_{except struct expression}

whereas for e.g. match EXPR { .. } or if let PATTERN = EXPR { .. }, there's a more "meaningful name" for that EXPR, which is the scrutinee expr.

Footnotes

1. In the community discord, terms like "interatee" or "iterable" or "into-iterable" were suggested, but yeah. ↩

2. Nadrieril came up with "loopee", which is an excellent term 😆 ↩