Issue #21661 has been updated by Earlopain (Earlopain _). It isn't specifically about block locals, `p do |a = def f = 1, b| end` is the same. `p do |a = def f = 1| 2; b|c end` becomes `p do |a = (def f = 1| 2); b|c end`, so one block local `b` and method body of `c`. The same issue as the first example I believe. That said, it looks inconsistent in parse.y: `def foo(a = def f = 1, b); end` and `->(a = def f = 1; b) {}` is accepted. Why is it ok in method and lamba parameters but not in block parameters? I feel like it should be rejected in all these cases. ---------------------------------------- Bug #21661: Endless method definition as a default value of block parameter is wrongly accepted in Prism https://bugs.ruby-lang.org/issues/21661#change-115029 * Author: tompng (tomoya ishida) * Status: Open * Assignee: prism * ruby -v: ruby 3.5.0dev (2025-11-01T00:18:01Z master 17a7b4e031) +PRISM [x86_64-linux] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- These are syntax error in parse.y but not in Prism. ~~~ruby p do |a = def f = 1; b| end p do |a = def f = 1| 2; b|c end # `|` inside block parameter ~~~ Normal assignment as a default value `p do |a = b = 1| end` is already syntax error. -- https://bugs.ruby-lang.org/