From 64bb14a2cd8ab74fb709effffe4ed5b3b2ecaa36 Mon Sep 17 00:00:00 2001
From: Copilot <198982749+Copilot@users.noreply.github.com>
Date: Wed, 4 Mar 2026 07:07:46 -0800
Subject: [PATCH] Fix `redundantSendable` incorrectly removing `Sendable` from
 types inside `public extension` (#2423)

Co-authored-by: calda <1811727+calda@users.noreply.github.com>
---
 Sources/Rules/RedundantSendable.swift    | 10 ++++++-
 Tests/Rules/RedundantSendableTests.swift | 33 ++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/Sources/Rules/RedundantSendable.swift b/Sources/Rules/RedundantSendable.swift
index e356cbee..03b7abaf 100644
--- a/Sources/Rules/RedundantSendable.swift
+++ b/Sources/Rules/RedundantSendable.swift
@@ -21,8 +21,16 @@ public extension FormatRule {
             switch typeDeclaration.visibility() {
             case .public, .open:
                 return
-            case .internal, .package, .fileprivate, .private, nil:
+            case .internal, .package, .fileprivate, .private:
                 break
+            case nil:
+                // A type with no explicit access modifier inside a public extension is effectively public
+                let isInPublicExtension = typeDeclaration.parentDeclarations.last.map {
+                    $0.keyword == "extension" && $0.visibility() == .public
+                } ?? false
+                if isInPublicExtension {
+                    return
+                }
             }
 
             guard let sendableConformance = typeDeclaration.conformances.first(where: {
diff --git a/Tests/Rules/RedundantSendableTests.swift b/Tests/Rules/RedundantSendableTests.swift
index 60dca028..7d97bc5e 100644
--- a/Tests/Rules/RedundantSendableTests.swift
+++ b/Tests/Rules/RedundantSendableTests.swift
@@ -93,6 +93,39 @@ final class RedundantSendableTests: XCTestCase {
         testFormatting(for: input, [output], rules: [.redundantSendable])
     }
 
+    func testDoesNotRemoveSendableFromTypeInsidePublicExtension() {
+        let input = """
+        public struct OuterStruct {}
+
+        public extension OuterStruct {
+            struct InnerStruct: Sendable {}
+            enum InnerEnum: Sendable {}
+        }
+        """
+
+        testFormatting(for: input, rules: [.redundantSendable])
+    }
+
+    func testRemovesSendableFromTypeInsideInternalExtension() {
+        let input = """
+        struct OuterStruct {}
+
+        extension OuterStruct {
+            struct InnerStruct: Sendable {}
+        }
+        """
+
+        let output = """
+        struct OuterStruct {}
+
+        extension OuterStruct {
+            struct InnerStruct {}
+        }
+        """
+
+        testFormatting(for: input, [output], rules: [.redundantSendable])
+    }
+
     func testRemovesSendableFromPackageValueTypes() {
         let input = """
         package struct PackageStruct: Sendable {