Bug #20974: Required and optional anonymous parameter show differently in Proc#parameters

• Status: Open
• Assignee: -
• Target version: -
• Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN

[alanwu (Alan Wu)]

The following has had the same output since Ruby 1.9, when Proc#parameters was introduced:

p(proc   { |(_a)| }.parameters) # => [[:opt, nil]]
p(lambda { |(_a)| }.parameters) # => [[:req]]

I think they should be [[:opt]] and [[:req]] or [[:opt, nil]] and [[:req, nil]]. I prefer the nil-free option since that feels more anonymous.

[alanwu (Alan Wu)]

• Related to Bug #20955: Subtle differences with Proc#parameters for anonymous parameters added

[alanwu (Alan Wu)]

• Description updated (diff)

[alanwu (Alan Wu)]

It's not hard to patch this small issue. We need consensus on whether this is an issue and what the new behavior should be, though.

diff --git a/iseq.c b/iseq.c
index 639ca3a4cd..d5808b81a5 100644
--- a/iseq.c
+++ b/iseq.c
@@ -3606,7 +3606,9 @@ rb_iseq_parameters(const rb_iseq_t *iseq, int is_proc)
     if (is_proc) {
         for (i = 0; i < body->param.lead_num; i++) {
             PARAM_TYPE(opt);
-            rb_ary_push(a, rb_id2str(PARAM_ID(i)) ? ID2SYM(PARAM_ID(i)) : Qnil);
+            if (rb_id2str(PARAM_ID(i))) {
+                rb_ary_push(a, ID2SYM(PARAM_ID(i)));
+            }
             rb_ary_push(args, a);
         }
     }