Issue #20043 has been updated by byroot (Jean Boussier).
Is there any use case for defined? besides those?
Instance variables for sure: `defined?(@ivar)`. Also checking for super: `defined?(super)`. Some people use it for a sequence of calls: `defined?(foo.bar.baz)`. ---------------------------------------- Bug #20043: `defined?` checks for method existence but only sometimes https://bugs.ruby-lang.org/issues/20043#change-105540 * Author: tenderlovemaking (Aaron Patterson) * Status: Open * Priority: Normal * ruby -v: ruby 3.3.0dev (2023-12-05T21:25:34Z master 56eccb350b) [arm64-darwin23] * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- When an expression is passed to `defined?`, it will _sometimes_ check if a method in a sub-expression is defined and sometimes it won't. For example: ``` $ ./miniruby -e'p defined?(a)' nil $ ./miniruby -e'p defined?([a])' nil ``` In the above case, Ruby will check whether or not the method `a` is defined, and it returns `nil`. However, if you use a splat, it will not check: ``` $ ./miniruby -e'p defined?([*a])' "expression" ``` The same thing seems to happen with method parameters: ``` $ ./miniruby -e'p defined?(itself)' "method" $ ./miniruby -e'p defined?(itself(a))' nil $ ./miniruby -e'p defined?(itself(*a))' "method" ``` Oddly, `defined?` will check contents of arrays, but _won't_ check contents of hashes: ``` $ ./miniruby -e'p defined?([[[[a]]]])' nil $ ./miniruby -e'p defined?({ a => a })' "expression" ``` I think all of the cases that refer to `a` should check whether or not `a` is defined regardless of splats or hashes. -- https://bugs.ruby-lang.org/