Patch Void type handling in Sorbet runtime for correct return types

Since sorbet/sorbet#10064 was merged, for any sig that declares `.void.checked(:tests)`, the runtime will treat the return type as `T.anything` instead of `void` and thus break Tapioca's signature generation for methods that use this pattern.

This commit adds a patch to the Sorbet runtime to ensure that the return type is correctly treated as `void` in these cases, allowing Tapioca to generate accurate signatures.

Author: paracycle

lib/tapioca/internal.rb

@@ -13,6 +13,7 @@
 require "tapioca/sorbet_ext/name_patch"
 require "tapioca/sorbet_ext/generic_name_patch"
 require "tapioca/sorbet_ext/proc_bind_patch"
+require "tapioca/sorbet_ext/void_patch"
 require "tapioca/runtime/generic_type_registry"
 
 # The rewriter needs to be loaded very early so RBS comments within Tapioca itself are rewritten

lib/tapioca/sorbet_ext/void_patch.rb

@@ -0,0 +1,29 @@
+# typed: true
+# frozen_string_literal: true
+
+# If Signature has `effective_return_type`, then `return_type` always returns the correct type.
+# Ref: https://github.com/sorbet/sorbet/pull/10121
+return if T::Private::Methods::Signature.method_defined?(:effective_return_type)
+
+module T
+  module Private
+    module Methods
+      module DeclBuilderPatch
+        def void
+          super.tap do
+            @_real_returns_is_void = true
+          end
+        end
+
+        def finalize!
+          super.tap do
+            #: self as untyped
+            decl.returns = T::Private::Types::Void::Private::INSTANCE if @_real_returns_is_void
+          end
+        end
+      end
+
+      DeclBuilder.prepend(DeclBuilderPatch)
+    end
+  end
+end

sorbet/rbi/shims/sorbet.rbi

@@ -14,7 +14,13 @@ module T::Private
     def self.sealed_module?(mod); end
   end
 
-  class Types::NotTyped < T::Types::Base; end
+  module Types
+    class NotTyped < T::Types::Base; end
+
+    module Void::Private
+      INSTANCE = T.let(T.unsafe(nil), T::Private::Types::Void)
+    end
+  end
 
   module Methods
     ARG_NOT_PROVIDED = T.let(T.unsafe(nil), Object)
@@ -53,6 +59,8 @@ module T::Private
       def finalized; end
       def finalized=(finalized); end
     end
+
+    class Signature; end
   end
 
   module DeclState

spec/tapioca/gem/pipeline_spec.rb

@@ -4627,6 +4627,32 @@ def foo; end
       assert_equal(output, compiled)
     end
 
+    it "compiles methods with .void.checked(:tests) properly" do
+      add_ruby_file("bar.rb", <<~RUBY)
+        class Bar
+          extend T::Sig
+
+          sig { params(x: Integer).void.checked(:tests) }
+          def initialize(x); end
+
+          sig { void.checked(:tests) }
+          def foo; end
+        end
+      RUBY
+
+      output = template(<<~RBI)
+        class Bar
+          sig { params(x: ::Integer).void }
+          def initialize(x); end
+
+          sig { void }
+          def foo; end
+        end
+      RBI
+
+      assert_equal(output, compile)
+    end
+
     it "compiles constants with nil values" do
       add_ruby_file("foo.rb", <<~RUBY)
         class Foo