From: daniel@...42.com Date: 2019-10-22T18:00:35+00:00 Subject: [ruby-core:95472] [Ruby master Feature#16166] Remove exceptional treatment of *foo when it is the sole block parameter Issue #16166 has been updated by Dan0042 (Daniel DeLorme). I think this is related: ```ruby proc{ |a,b| [a,b] }.call(1,2) #=> [1, 2] proc{ |*ab| ab }.call(1,2) #=> [1, 2] proc{ |a,b| [a,b] }.call([1,2]) #=> [1, 2] proc{ |*ab| ab }.call([1,2]) #=> [[1, 2]] ``` I *really* think the last result should be [1, 2]. Otherwise I totally fail to understand the logic. But of course there's always backward compatibility to worry about... ---------------------------------------- Feature #16166: Remove exceptional treatment of *foo when it is the sole block parameter https://bugs.ruby-lang.org/issues/16166#change-82242 * 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: