Issue #20478 has been updated by nobu (Nobuyoshi Nakada). Even this should be a syntax error? ```ruby def foo(bar = ->(baz = bar) {}) end ``` That means it needs to manage the list of yet-unusable variables, not only tracking single variable. ---------------------------------------- Bug #20478: Circular parameter syntax error rules https://bugs.ruby-lang.org/issues/20478#change-108242 * Author: kddnewton (Kevin Newton) * Status: Open * Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- I would like to revisit https://bugs.ruby-lang.org/issues/16343. These cases are syntax errors: ```ruby def foo(bar = -> { bar }) end # no lambda parameters def foo(bar = ->() { bar }) end # no lambda parameters def foo(bar = baz { bar }) end # no block parameters def foo(bar = baz { _1 + bar }) end # parameters, but no pipes def foo(bar = baz { it + bar }) end # parameters, but no pipes ``` These cases are not syntax errors: ```ruby def foo(bar = ->(baz) { bar }) end # lambda parameters def foo(bar = baz { || bar }) end # no block parameters but empty pipes def foo(bar = baz { |qux| bar }) end # block parameters ``` I don't think these rules are very intuitive, and they feel somewhat arbitrary. I would like to suggest we change them to be either: * Syntax error is raised if the parameter is ever read in its default value at any scope depth * Syntax error is raised if the parameter is ever read in its default value at depth 0 Either one is fine by me, but gating the syntax error based on the presence of pipes is really confusing. -- https://bugs.ruby-lang.org/