Issue #16166 has been updated by jeremyevans0 (Jeremy Evans). matz (Yukihiro Matsumoto) wrote: > I think the following code behavior is wrong: > ```ruby > p instance_exec(["a"]){|*foo, **bar| foo } #=> ["a"] > ``` > It should return `[["a"]]`. Here's a pull request for that: https://github.com/ruby/ruby/pull/2502 Note that it breaks some tests/specs. I believe the reason methods with keywords were handled differently is because the last element of the argument could be used as keywords: ``` $ ruby -e "p proc{|*foo, **bar| [foo, bar]}.call([1, {a: 1}])" -e:1: warning: The last argument is used as the keyword parameter -e:1: warning: for `call' defined here [[1], {:a=>1}] ``` As you can see, this now raises a warning in Ruby 2.7, and behavior will change in Ruby 3.0. Do we want to make this change in 2.7, or do we want to wait for 3.0? ---------------------------------------- Feature #16166: Remove exceptional treatment of *foo when it is the sole block parameter https://bugs.ruby-lang.org/issues/16166#change-81778 * Author: sawa (Tsuyoshi Sawada) * Status: Open * Priority: Normal * Assignee: * Target version: ---------------------------------------- In the parameter signature of a code block for a method that is not involved in method definition or creation of lambda objects, two types of arguments `["a"]` and `"a"` are neutralized: ```ruby instance_exec(["a"]){|foo, bar| foo} # => "a" instance_exec("a"){|foo, bar| foo} # => "a" instance_exec(["a"]){|*foo, **bar| foo} # => ["a"] instance_exec("a"){|*foo, **bar| foo} # => ["a"] ``` This is the same behavior as with assignment constructions: ```ruby foo, bar = ["a"]; foo # => "a" foo, bar = "a"; foo # => "a" *foo = ["a"]; foo # => ["a"] *foo = "a"; foo # => ["a"] ``` And it contrasts with constructions involved in method definition or creation of lambda objects, where the distinction is preserved: ```ruby lambda{|foo| foo}.call(["a"]) # => ["a"] lambda{|foo| foo}.call("a") # => "a" ->(foo){foo}.call(["a"]) # => ["a"] ->(foo){foo}.call("a") # => "a" lambda{|*foo| foo}.call(["a"]) # => [["a"]] lambda{|*foo| foo}.call("a") # => ["a"] ->(*foo){foo}.call(["a"]) # => [["a"]] ->(*foo){foo}.call("a") # => ["a"] ``` However, when `*foo` is the sole parameter of a code block for a method that is not involved in method definition or creation of lambda objects, `["a"]` and `"a"` are not neutralized: ```ruby instance_exec(["a"]){|*foo| foo} # => [["a"]] instance_exec("a"){|*foo| foo} # => ["a"] ``` behaving in contrast to assignment constructions, and rather on a par with constructions involved in method definition or creation of lambda objects. Particularly, existence or absence of another parameter `**bar` entirely changes what `foo` refers to: ```ruby instance_exec(["a"]){|*foo| foo} # => [["a"]] instance_exec(["a"]){|*foo, **bar| foo} # => ["a"] ``` I find this behavior inconsistent and confusing. I would like to request to remove this exceptional treatment of splatted parameter `*foo` when it is the sole parameter in a code block. I request this behavior: ```ruby instance_exec(["a"]){|*foo| foo} # => ["a"] ``` -- https://bugs.ruby-lang.org/ Unsubscribe: <mailto:ruby-core-request / ruby-lang.org?subject=unsubscribe> <http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>