1 files changed, 55 insertions, 5 deletions

diff --git a/lib/Sema/SemaDeclAttr.cpp b/lib/Sema/SemaDeclAttr.cpp
index b43642f5493b..e8503427536d 100644
--- a/lib/Sema/SemaDeclAttr.cpp
+++ b/lib/Sema/SemaDeclAttr.cpp
@@ -6903,6 +6903,32 @@ static bool ShouldDiagnoseAvailabilityInContext(Sema &S, AvailabilityResult K,
   return true;
 }
 
+static bool
+shouldDiagnoseAvailabilityByDefault(const ASTContext &Context,
+                                    const VersionTuple &DeploymentVersion,
+                                    const VersionTuple &DeclVersion) {
+  const auto &Triple = Context.getTargetInfo().getTriple();
+  VersionTuple ForceAvailabilityFromVersion;
+  switch (Triple.getOS()) {
+  case llvm::Triple::IOS:
+  case llvm::Triple::TvOS:
+    ForceAvailabilityFromVersion = VersionTuple(/*Major=*/11);
+    break;
+  case llvm::Triple::WatchOS:
+    ForceAvailabilityFromVersion = VersionTuple(/*Major=*/4);
+    break;
+  case llvm::Triple::Darwin:
+  case llvm::Triple::MacOSX:
+    ForceAvailabilityFromVersion = VersionTuple(/*Major=*/10, /*Minor=*/13);
+    break;
+  default:
+    // New targets should always warn about availability.
+    return Triple.getVendor() == llvm::Triple::Apple;
+  }
+  return DeploymentVersion >= ForceAvailabilityFromVersion ||
+         DeclVersion >= ForceAvailabilityFromVersion;
+}
+
 static void DoEmitAvailabilityWarning(Sema &S, AvailabilityResult K,
                                       Decl *Ctx, const NamedDecl *D,
                                       StringRef Message, SourceLocation Loc,
@@ -6991,13 +7017,26 @@ static void DoEmitAvailabilityWarning(Sema &S, AvailabilityResult K,
     }
     break;
 
-  case AR_NotYetIntroduced:
-    diag = diag::warn_partial_availability;
-    diag_message = diag::warn_partial_message;
-    diag_fwdclass_message = diag::warn_partial_fwdclass_message;
+  case AR_NotYetIntroduced: {
+    // We would like to emit the diagnostic even if -Wunguarded-availability is
+    // not specified for deployment targets >= to iOS 11 or equivalent or
+    // for declarations that were introduced in iOS 11 (macOS 10.13, ...) or
+    // later.
+    const AvailabilityAttr *AA = getAttrForPlatform(S.getASTContext(), D);
+    VersionTuple Introduced = AA->getIntroduced();
+    bool NewWarning = shouldDiagnoseAvailabilityByDefault(
+        S.Context, S.Context.getTargetInfo().getPlatformMinVersion(),
+        Introduced);
+    diag = NewWarning ? diag::warn_partial_availability_new
+                      : diag::warn_partial_availability;
+    diag_message = NewWarning ? diag::warn_partial_message_new
+                              : diag::warn_partial_message;
+    diag_fwdclass_message = NewWarning ? diag::warn_partial_fwdclass_message_new
+                                       : diag::warn_partial_fwdclass_message;
     property_note_select = /* partial */ 2;
     available_here_select_kind = /* partial */ 3;
     break;
+  }
 
   case AR_Available:
     llvm_unreachable("Warning for availability of available declaration?");
@@ -7317,7 +7356,18 @@ void DiagnoseUnguardedAvailability::DiagnoseDeclAvailability(
     if (!ShouldDiagnoseAvailabilityInContext(SemaRef, Result, Introduced, Ctx))
       return;
 
-    SemaRef.Diag(Range.getBegin(), diag::warn_unguarded_availability)
+    // We would like to emit the diagnostic even if -Wunguarded-availability is
+    // not specified for deployment targets >= to iOS 11 or equivalent or
+    // for declarations that were introduced in iOS 11 (macOS 10.13, ...) or
+    // later.
+    unsigned DiagKind =
+        shouldDiagnoseAvailabilityByDefault(
+            SemaRef.Context,
+            SemaRef.Context.getTargetInfo().getPlatformMinVersion(), Introduced)
+            ? diag::warn_unguarded_availability_new
+            : diag::warn_unguarded_availability;
+
+    SemaRef.Diag(Range.getBegin(), DiagKind)
         << Range << D
         << AvailabilityAttr::getPrettyPlatformName(
                SemaRef.getASTContext().getTargetInfo().getPlatformName())