From f0fd5067459c37009e8c9b1d669e7428359fb276 Mon Sep 17 00:00:00 2001
From: Pavel Yaskevich <pyaskevich@apple.com>
Date: Fri, 5 Dec 2025 17:12:37 -0800
Subject: [PATCH] [Diagnostics] TildeSendable: Suggest `Sendable` suppression
 in explicit Senable warning

Add a note to missing explicit `Sendable` conformance warning
(produced by `-Wwarning ExplicitSendable`) and a fix-it with
a suggestion to suppress `Senable` conformance  via `~Sendable`.
---
 include/swift/AST/DiagnosticsSema.def |  3 +++
 lib/Sema/TypeCheckConcurrency.cpp     | 11 +++++++++++
 test/Sema/tilde_sendable.swift        | 18 +++++++++++++++++-
 3 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/include/swift/AST/DiagnosticsSema.def b/include/swift/AST/DiagnosticsSema.def
index 116e11f825d1e..18c57099ae575 100644
--- a/include/swift/AST/DiagnosticsSema.def
+++ b/include/swift/AST/DiagnosticsSema.def
@@ -8987,6 +8987,9 @@ NOTE(sendable_conformance_is_suppressed, none,
      "%kind0 explicitly suppresses conformance to 'Sendable' protocol",
      (const NominalTypeDecl *))
 
+NOTE(suppress_sendable_conformance,none,
+     "consider suppressing conformance to 'Sendable' protocol", ())
+
 ERROR(non_sendable_type_suppressed,none,
       "cannot both conform to and suppress conformance to 'Sendable'", ())
 
diff --git a/lib/Sema/TypeCheckConcurrency.cpp b/lib/Sema/TypeCheckConcurrency.cpp
index 1fa26a342f119..a7937c445a4a3 100644
--- a/lib/Sema/TypeCheckConcurrency.cpp
+++ b/lib/Sema/TypeCheckConcurrency.cpp
@@ -1453,6 +1453,17 @@ void swift::diagnoseMissingExplicitSendable(NominalTypeDecl *nominal) {
     }
   }
 
+  // Note to supress Sendable conformance is feature is enabled.
+  if (ctx.LangOpts.hasFeature(Feature::TildeSendable)) {
+    auto note = nominal->diagnose(diag::suppress_sendable_conformance);
+    auto inheritance = nominal->getInherited();
+    if (inheritance.empty()) {
+      note.fixItInsertAfter(nominal->getNameLoc(), ": ~Sendable");
+    } else {
+      note.fixItInsertAfter(inheritance.getEndLoc(), ", ~Sendable");
+    }
+  }
+
   // Note to disable the warning.
   {
     auto note = nominal->diagnose(diag::explicit_disable_sendable, nominal);
diff --git a/test/Sema/tilde_sendable.swift b/test/Sema/tilde_sendable.swift
index 0e1be14a6535e..7c5de87fd0285 100644
--- a/test/Sema/tilde_sendable.swift
+++ b/test/Sema/tilde_sendable.swift
@@ -1,4 +1,4 @@
-// RUN: %target-typecheck-verify-swift -strict-concurrency=complete -swift-version 5 -enable-experimental-feature TildeSendable
+// RUN: %target-typecheck-verify-swift -strict-concurrency=complete -swift-version 5 -enable-experimental-feature TildeSendable -Wwarning ExplicitSendable
 
 // REQUIRES: swift_feature_TildeSendable
 
@@ -136,3 +136,19 @@ do {
     // expected-error@-1 {{conformance to 'Sendable' can only be suppressed on structs, classes, and enums}}
   }
 }
+
+// ExplicitSendable + ~Sendable tests
+
+public struct TestExplicitSendable1 { // expected-warning {{public struct 'TestExplicitSendable1' does not specify whether it is 'Sendable' or not}}
+  // expected-note@-1 {{consider making struct 'TestExplicitSendable1' conform to the 'Sendable' protocol}}
+  // expected-note@-2 {{consider suppressing conformance to 'Sendable' protocol}} {{36-36=: ~Sendable}}
+  // expected-note@-3 {{make struct 'TestExplicitSendable1' explicitly non-Sendable to suppress this warning}}
+}
+
+public class TestExplicitSendableWithParent: ExpressibleByIntegerLiteral { // expected-warning {{public class 'TestExplicitSendableWithParent' does not specify whether it is 'Sendable' or not}}
+  // expected-note@-1 {{consider suppressing conformance to 'Sendable' protocol}} {{73-73=, ~Sendable}}
+  // expected-note@-2 {{make class 'TestExplicitSendableWithParent' explicitly non-Sendable to suppress this warning}}
+
+  public required init(integerLiteral: Int) {
+  }
+}