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 😆 ↩

[iampi31415]

Do they all need a name though?

Should the borrow expression call it borrowee ?

And the deref expression, dereferencee ? (We may use pointer here, but you get the gist.)

Just say what EXPR can be, which is done in the document.

IteratorLoopExpression :
for Pattern in Expression _{except struct expression} BlockExpression

And to an extent, the traditional iterator seems fine to me, but I'd not add an extra label.

for expression extracts values from an iterator, looping until the iterator is empty.