From: sawadatsuyoshi@... Date: 2020-01-05T16:06:12+00:00 Subject: [ruby-core:96671] [Ruby master Feature#16166] Remove exceptional treatment of *foo when it is the sole block parameter Issue #16166 has been updated by sawa (Tsuyoshi Sawada). [The log for developers' meeting 20191128](https://docs.google.com/document/d/1AZ74HXEedKksJwhEUPIlnRxAUgchndZPZYAKjGPMsFI/edit#) says that Matz hoped this to be done in 2.7. However, Ruby 2.7 still returns this: ```ruby instance_exec(["a"]){|*foo, **bar| foo } #=> ["a"] ``` Likely forgotten? Perhaps, it can be done by the next release (2.8 or 3.0). ---------------------------------------- Feature #16166: Remove exceptional treatment of *foo when it is the sole block parameter https://bugs.ruby-lang.org/issues/16166#change-83654 * 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: