From 7ac93e99a3db30ed41cbbe95df1d7be9a790b9cb Mon Sep 17 00:00:00 2001
From: Jemma Issroff <jemmaissroff@gmail.com>
Date: Wed, 13 Dec 2023 12:17:22 -0500
Subject: [PATCH] [PRISM] Account for multiple anonymous locals

This commit adjusts the local table size to be consistent regardless
of the number of anonymous locals.
---
 prism_compile.c                 | 14 ++++++++++++++
 test/ruby/test_compile_prism.rb |  2 ++
 2 files changed, 16 insertions(+)

diff --git a/prism_compile.c b/prism_compile.c
index c629fdfc610a08..b86b4760b00ab3 100644
--- a/prism_compile.c
+++ b/prism_compile.c
@@ -4489,6 +4489,7 @@ pm_compile_node(rb_iseq_t *iseq, const pm_node_t *node, LINK_ANCHOR *const ret,
         }
 
         if (requireds_list) {
+            int number_of_anonymous_locals = 0;
             for (size_t i = 0; i < requireds_list->size; i++) {
                 // For each MultiTargetNode, we're going to have one
                 // additional anonymous local not represented in the locals table
@@ -4497,6 +4498,19 @@ pm_compile_node(rb_iseq_t *iseq, const pm_node_t *node, LINK_ANCHOR *const ret,
                 if (PM_NODE_TYPE_P(required, PM_MULTI_TARGET_NODE)) {
                     table_size++;
                 }
+                else if (PM_NODE_TYPE_P(required, PM_REQUIRED_PARAMETER_NODE)) {
+                    if (pm_constant_id_lookup(scope_node, ((pm_required_parameter_node_t *)required)->name) == rb_intern("_")) {
+                        number_of_anonymous_locals++;
+                    }
+                }
+            }
+
+            // For each anonymous local we also want to increase the size
+            // of the locals table. Prism's locals table accounts for all
+            // anonymous locals as 1, so we need to increase the table size
+            // by the number of anonymous locals - 1
+            if (number_of_anonymous_locals > 1) {
+                table_size += (number_of_anonymous_locals - 1);
             }
         }
 
diff --git a/test/ruby/test_compile_prism.rb b/test/ruby/test_compile_prism.rb
index f89aabfc0e5637..192094bafe1975 100644
--- a/test/ruby/test_compile_prism.rb
+++ b/test/ruby/test_compile_prism.rb
@@ -1128,6 +1128,8 @@ def test_BlockNode
       assert_prism_eval("[].tap { _1 }")
 
       assert_prism_eval("[].each { |a,| }")
+      assert_prism_eval("[[1, 2, 3]].map { |_, _, a| a }")
+      assert_prism_eval("[[1, 2, 3]].map { |_, a| a }")
 
       assert_prism_eval("[[]].map { |a| a }")
       assert_prism_eval("[[]].map { |a| a }")