From 22f23a378b2d9f6101fa63667a7e13ab56d3568b Mon Sep 17 00:00:00 2001
From: Takeshi KOMIYA <i.tkomiya@gmail.com>
Date: Mon, 30 Sep 2024 18:57:34 +0900
Subject: [PATCH] stdlib: Make the block arguments of Kernel#proc untyped

This changes the block argument of `Kernel#proc` to UntypedFunction.
Then the arguments of the block become untyped instead of nil.

It allows users to override the type via comment annotation.

For example:

```
proc do |a, b, c|
  # @type var a: String
  # @type var b: Integer
  # @type var c: Symbol
end
```

I found this problem on the Steep repo.
https://github.com/soutaro/steep/blob/v1.8.0/lib/steep.rb#L169-L176
---
 core/kernel.rbs            | 2 +-
 test/stdlib/Kernel_test.rb | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/core/kernel.rbs b/core/kernel.rbs
index dd1f624fd..f97b66fd6 100644
--- a/core/kernel.rbs
+++ b/core/kernel.rbs
@@ -1209,7 +1209,7 @@ module Kernel : BasicObject
   # -->
   # Equivalent to Proc.new.
   #
-  def self?.proc: () { () -> untyped } -> Proc
+  def self?.proc: () { (?) -> untyped } -> Proc
 
   # <!--
   #   rdoc-file=proc.c
diff --git a/test/stdlib/Kernel_test.rb b/test/stdlib/Kernel_test.rb
index 137726110..bd8e40e08 100644
--- a/test/stdlib/Kernel_test.rb
+++ b/test/stdlib/Kernel_test.rb
@@ -95,6 +95,11 @@ def test_autoload?
     end
   end
 
+  def test_proc
+    assert_send_type "() { () -> untyped } -> Proc", Kernel, :proc do end
+    assert_send_type "() { () -> untyped } -> Proc", Kernel, :proc do |a, b| end
+  end
+
   def test_rand
     assert_send_type "() -> Float", Kernel, :rand
     assert_send_type "(0) -> Float", Kernel, :rand, 0