Issue #20478 has been updated by kddnewton (Kevin Newton). If we go with only syntax errors at depth 0, then this: ```ruby def foo(bar = baz { bar }) end ``` should not be a syntax error either. I think that makes sense, because the `baz` method could use `instance_exec`/`instance_eval` so we don't know if `bar` is going to be the same variable here or not. ---------------------------------------- Bug #20478: Circular parameter syntax error rules https://bugs.ruby-lang.org/issues/20478#change-108410 * 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/