From: "vinistock (Vinicius Stock) via ruby-core" Date: 2025-07-28T17:17:28+00:00 Subject: [ruby-core:122873] [Ruby Bug#21139] Prism and parse.y parses `it = it` differently Issue #21139 has been updated by vinistock (Vinicius Stock). No, I don't mean all variables. However, the `it` case feels unintuitive because `it` refers to the first argument of the block. Take this other example here: ```ruby 42.tap { it = it; p it } 42.tap { |x| x = x; p x } ``` To me, these two are exact equivalents. You are storing the first argument of the block in a local variable that shadows the name of that argument. Right now, `parse.y` returns different results for these two cases, which to me is quite surprising. If you run that snippet with `parse.y`, you get `nil` and `42`. The way I reason about this code is as follows: ```ruby 42.tap do it = it # ^ First step: read the value of `it`, which is the block's argument and therefore is equal to 42 # ^ Second step: declare a local variable called `it` and store the value of the right hand side (which is 42) p it # ^ Third step: at this point `it` no longer refers to the special variable `it`, but to a local variable `it`, for which the value is currently 42 end ``` > I think it would be far simpler to forbid it as a local variable name, though the compatibility implications would need to be carefully considered. Maybe this is a better path forward as these edge cases can be confusing. That said, I still think that the current behaviour in Prism is more intuitive and consistent. ---------------------------------------- Bug #21139: Prism and parse.y parses `it = it` differently https://bugs.ruby-lang.org/issues/21139#change-114176 * 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/ ______________________________________________ ruby-core mailing list -- ruby-core@ml.ruby-lang.org To unsubscribe send an email to ruby-core-leave@ml.ruby-lang.org ruby-core info -- https://ml.ruby-lang.org/mailman3/lists/ruby-core.ml.ruby-lang.org/