From 1649b5ec45ef1f08fbdcdb923aa95ac831a99911 Mon Sep 17 00:00:00 2001
From: Pavel Yaskevich <pyaskevich@apple.com>
Date: Mon, 24 Feb 2025 18:03:35 -0800
Subject: [PATCH 1/2] [Concurrency] Avoid dowgrading diagnostics multiple times

Unify `warn` + `limitBehavior` into a single call to make sure
that diagnostic doesn't get downgraded multiple times because
that could affect how diagnostics are tracked.
---
 lib/Sema/TypeCheckAvailability.cpp |  7 ++++--
 lib/Sema/TypeCheckConcurrency.cpp  | 39 +++++++++++++++++-------------
 2 files changed, 27 insertions(+), 19 deletions(-)

diff --git a/lib/Sema/TypeCheckAvailability.cpp b/lib/Sema/TypeCheckAvailability.cpp
index d40670b627c4c..e58ae673d8afc 100644
--- a/lib/Sema/TypeCheckAvailability.cpp
+++ b/lib/Sema/TypeCheckAvailability.cpp
@@ -2337,8 +2337,11 @@ diagnosePotentialUnavailability(const RootProtocolConformance *rootConf,
         ctx.getTargetPlatformStringForDiagnostics(),
         availability.getRawMinimumVersion());
 
-    err.warnUntilSwiftVersion(6);
-    err.limitBehavior(behaviorLimitForExplicitUnavailability(rootConf, dc));
+    auto behaviorLimit = behaviorLimitForExplicitUnavailability(rootConf, dc);
+    if (behaviorLimit >= DiagnosticBehavior::Warning)
+      err.limitBehavior(behaviorLimit);
+    else
+      err.warnUntilSwiftVersion(6);
 
     // Direct a fixit to the error if an existing guard is nearly-correct
     if (fixAvailabilityByNarrowingNearbyVersionCheck(loc, dc, availability, ctx,
diff --git a/lib/Sema/TypeCheckConcurrency.cpp b/lib/Sema/TypeCheckConcurrency.cpp
index 084196654c246..b989ce887f1ce 100644
--- a/lib/Sema/TypeCheckConcurrency.cpp
+++ b/lib/Sema/TypeCheckConcurrency.cpp
@@ -4853,14 +4853,12 @@ getIsolationFromAttributes(const Decl *decl, bool shouldDiagnose = true,
     bool isUnsafe = attr->isArgUnsafe();
     if (attr->hasArgs()) {
       if (isUnsafe) {
-        bool inSwiftinterface = decl->getDeclContext()->isInSwiftinterface();
-        ctx.Diags.diagnose(
-            attr->getLocation(),
-            diag::unsafe_global_actor)
-          .fixItRemove(attr->getArgs()->getSourceRange())
-          .fixItInsert(attr->getLocation(), "@preconcurrency ")
-          .warnUntilSwiftVersion(6)
-          .limitBehaviorIf(inSwiftinterface, DiagnosticBehavior::Ignore);
+        if (!decl->getDeclContext()->isInSwiftinterface()) {
+          ctx.Diags.diagnose(attr->getLocation(), diag::unsafe_global_actor)
+              .fixItRemove(attr->getArgs()->getSourceRange())
+              .fixItInsert(attr->getLocation(), "@preconcurrency ")
+              .warnUntilSwiftVersion(6);
+        }
       } else {
         ctx.Diags.diagnose(
             attr->getLocation(),
@@ -6490,11 +6488,14 @@ static bool checkSendableInstanceStorage(
               return true;
             }
 
-            property->diagnose(diag::non_concurrent_type_member,
-                               propertyType, false, property->getName(),
-                               nominal)
-                .limitBehaviorUntilSwiftVersion(behavior, 6)
-                .limitBehaviorIf(preconcurrency);
+            if (preconcurrency)
+              behavior = preconcurrency.value();
+
+            property
+                ->diagnose(diag::non_concurrent_type_member, propertyType,
+                           false, property->getName(), nominal)
+                .limitBehaviorWithPreconcurrency(behavior,
+                                                 preconcurrency.has_value());
             return false;
           });
 
@@ -6532,10 +6533,14 @@ static bool checkSendableInstanceStorage(
               return true;
             }
 
-            element->diagnose(diag::non_concurrent_type_member, type,
-                              true, element->getName(), nominal)
-                .limitBehaviorUntilSwiftVersion(behavior, 6)
-                .limitBehaviorIf(preconcurrency);
+            if (preconcurrency)
+              behavior = preconcurrency.value();
+
+            element
+                ->diagnose(diag::non_concurrent_type_member, type, true,
+                           element->getName(), nominal)
+                .limitBehaviorWithPreconcurrency(behavior,
+                                                 preconcurrency.has_value());
             return false;
           });
 

From 664c119e3085ba6a13d90493e8d7b3452b564c0d Mon Sep 17 00:00:00 2001
From: Pavel Yaskevich <pyaskevich@apple.com>
Date: Mon, 24 Feb 2025 18:04:55 -0800
Subject: [PATCH 2/2] [DiagnosticEngine] Don't account ignored diagnostics in
 `Sema.NumSwift6Errors` statistic

Since the diagnostic is not going to be emitted counting it in
`Swift6Errors` statistics is going to be confusing to the users.

Resolves: https://github.com/swiftlang/swift/issues/79291
Resolves: rdar://145341605
---
 lib/AST/DiagnosticEngine.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/AST/DiagnosticEngine.cpp b/lib/AST/DiagnosticEngine.cpp
index 599ff14369719..c6722f803f638 100644
--- a/lib/AST/DiagnosticEngine.cpp
+++ b/lib/AST/DiagnosticEngine.cpp
@@ -440,7 +440,8 @@ InFlightDiagnostic::limitBehaviorUntilSwiftVersion(
     limitBehavior(limit);
   }
 
-  if (majorVersion == 6) {
+  // Record all of the diagnostics that are going to be emitted.
+  if (majorVersion == 6 && limit != DiagnosticBehavior::Ignore) {
     if (auto stats = Engine->statsReporter) {
       ++stats->getFrontendCounters().NumSwift6Errors;
     }