Issue #21139 has been updated by mame (Yusuke Endoh). AMomchilov (Alexander Momchilov) wrote in #note-19:
Since `it` is just a shorthand for "the first block argument," then I think people would expect that it works _as if_ you declared `|it|` yourself.
I can understand that expectation. However, this would mean executing an assignment to the local variable `it` on every block evaluation. For this performance reason, @ko1 is against it, as mentioned here: https://bugs.ruby-lang.org/issues/20965#note-7 jeremyevans0 (Jeremy Evans) wrote in #note-20:
Personally, I think consistency is much more important in this case.
I agree with Jeremy. While we could debate the "intuitive" behavior of code like `{ it = it; p it }`, I believe no one would recommend such code. Therefore, I don't see the need to make it behave "intuitively." IMO, `it` should be used only for very small, obvious, single-line blocks, like `{ it + 1 }` or `{ foo(it) }`. I believe that any block containing an assignment should use an explicit parameter name instead of `it`. Furthermore, Matz said "Assignment to `it` should be prohibited in the long run." (This is a difficult decision, however, as an amount of existing code uses `it` as a local variable name.) Considering all the above, I believe it is better to maintain consistency with the existing semantics of `x = x`, rather than introducing an ad-hoc syntactic exception to satisfy an "intuitive" expectation for a piece of code that is itself not recommended. ---------------------------------------- Bug #21139: Prism and parse.y parses `it = it` differently https://bugs.ruby-lang.org/issues/21139#change-114184 * Author: tompng (tomoya ishida) * Status: Feedback * Assignee: prism * ruby -v: ruby 3.5.0dev (2025-02-14T16:49:52Z master ee181d1bb7) +PRISM [x86_64-linux] * Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- ~~~ # ruby --parser=parse.y -e "42.tap { it = it; p it }" nil # ruby --parser=prism -e "42.tap { it = it; p it }" 42 ~~~ ---Files-------------------------------- clipboard-202503081702-idzz2.png (22.6 KB) -- https://bugs.ruby-lang.org/