https://git.ruby-lang.org/ruby.git/commit/?id=8f1c69f27c

From 8f1c69f27ce6b3f5ed1c1cf8d2aa62aa9701d636 Mon Sep 17 00:00:00 2001
From: Jeremy Evans <code@j...>
Date: Tue, 22 Mar 2022 12:45:51 -0700
Subject: Raise ArgumentError when calling Enumberable#inject without block or
 arguments

Previously, this would work as expected if the enumerable contained
0 or 1 element, and would raise LocalJumpError otherwise. That
inconsistent behavior is likely to lead to bugs.

Fixes [Bug #18635]
---
 enum.c                 | 10 +++++++++-
 test/ruby/test_enum.rb |  2 ++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/enum.c b/enum.c
index 519d8873f6..383619999b 100644
--- a/enum.c
+++ b/enum.c
@@ -1010,8 +1010,16 @@ enum_inject(int argc, VALUE *argv, VALUE obj) https://github.com/ruby/ruby/blob/trunk/enum.c#L1010
     VALUE init, op;
     rb_block_call_func *iter = inject_i;
     ID id;
+    int num_args;
 
-    switch (rb_scan_args(argc, argv, "02", &init, &op)) {
+    if (rb_block_given_p()) {
+        num_args = rb_scan_args(argc, argv, "02", &init, &op);
+    }
+    else {
+        num_args = rb_scan_args(argc, argv, "11", &init, &op);
+    }
+
+    switch (num_args) {
       case 0:
 	init = Qundef;
 	break;
diff --git a/test/ruby/test_enum.rb b/test/ruby/test_enum.rb
index b0c43b9a7f..cc217b05cc 100644
--- a/test/ruby/test_enum.rb
+++ b/test/ruby/test_enum.rb
@@ -234,6 +234,8 @@ class TestEnumerable < Test::Unit::TestCase https://github.com/ruby/ruby/blob/trunk/test/ruby/test_enum.rb#L234
     assert_equal(24, @obj.inject(2) {|z, x| z * x })
     assert_equal(24, assert_warning(/given block not used/) {@obj.inject(2, :*) {|z, x| z * x }})
     assert_equal(nil, @empty.inject() {9})
+
+    assert_raise(ArgumentError) {@obj.inject}
   end
 
   FIXNUM_MIN = RbConfig::LIMITS['FIXNUM_MIN']
-- 
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