From: kazuki@... Date: 2021-08-15T11:53:01+00:00 Subject: [ruby-core:104923] [Ruby master Feature#16182] Should `expr in a, b, c` be allowed or not? Issue #16182 has been updated by ktsj (Kazuki Tsujimoto). How about allowing parentheses/brackets to be omitted in one-line pattern matching? Now that we use `=>` in one-line pattern matching, that syntax can't be made into an argument whether we allow omission or not. ---------------------------------------- Feature #16182: Should `expr in a, b, c` be allowed or not? https://bugs.ruby-lang.org/issues/16182#change-93291 * Author: mame (Yusuke Endoh) * Status: Open * Priority: Normal * Assignee: matz (Yukihiro Matsumoto) ---------------------------------------- In #15865, a new syntax ` in ` was introduced. By using this, we can write: ``` json = { foo: 1, bar: 2} if json in { foo:, bar: } p [foo, bar] #=> [1, 2] end ``` However, we cannot write: ``` p(json in { foo:, bar: }) #=> expected: true, actual: syntax error ``` This is because ` in ` is an expression but not an argument. For example, `foo(json in a, b, c)` is ambiguous: it is considered `foo((json in a), b, c)` and `foo((json in a, b, c))`. What should we do? 1. Do nothing; we admit that it is a spec 2. Revert the feature 3. Disallow a pattern like `a, b, c` or `a:, b:, c:` in this one-line pattern matching syntax; we ask a user to write `json in [a, b, c]` or `json in {a:, b:, c:}` -- https://bugs.ruby-lang.org/ Unsubscribe: