diff --git a/include/swift/AST/DiagnosticsSema.def b/include/swift/AST/DiagnosticsSema.def
index 54310001bb7c3..8b04951853c6a 100644
--- a/include/swift/AST/DiagnosticsSema.def
+++ b/include/swift/AST/DiagnosticsSema.def
@@ -6989,6 +6989,17 @@ WARNING(attr_availability_expected_version_spec, none,
 ERROR(attr_availability_requires_custom_availability, none,
       "%0 requires '-enable-experimental-feature CustomAvailability'",
       (AvailabilityDomain))
+ERROR(attr_availability_domain_access, none,
+      "availability domain '%0' is "
+      "%select{private|fileprivate|internal|package|%error|%error}1 "
+      "and cannot be used in '%2' on "
+      "%select{private|fileprivate|internal|package|public|%error}3 %kind4",
+      (AvailabilityDomain, AccessLevel, DeclAttribute, AccessLevel,
+       const Decl *))
+ERROR(attr_availability_domain_not_usable_from_inline, none,
+      "availability domain '%0' used in '%1' on %kind2 must be "
+      "'@usableFromInline' or public",
+      (AvailabilityDomain, DeclAttribute, const Decl *))
 
 ERROR(availability_decl_unavailable, none,
       "%0 is unavailable%select{ in %2|}1%select{|: %3}3",
diff --git a/lib/AST/AvailabilityDomain.cpp b/lib/AST/AvailabilityDomain.cpp
index db245ac22f9b2..f4329774b73da 100644
--- a/lib/AST/AvailabilityDomain.cpp
+++ b/lib/AST/AvailabilityDomain.cpp
@@ -41,9 +41,7 @@ getCustomDomainKind(clang::FeatureAvailKind featureAvailKind) {
 static const CustomAvailabilityDomain *
 customDomainForClangDecl(ValueDecl *decl) {
   auto *clangDecl = decl->getClangDecl();
-  ASSERT(clangDecl);
-
-  auto *varDecl = dyn_cast<clang::VarDecl>(clangDecl);
+  auto *varDecl = dyn_cast_or_null<clang::VarDecl>(clangDecl);
   if (!varDecl)
     return nullptr;
 
diff --git a/lib/AST/DiagnosticEngine.cpp b/lib/AST/DiagnosticEngine.cpp
index a26d6eafec562..00daeba9490bc 100644
--- a/lib/AST/DiagnosticEngine.cpp
+++ b/lib/AST/DiagnosticEngine.cpp
@@ -16,6 +16,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "swift/AST/DiagnosticEngine.h"
+#include "swift/AST/AvailabilityDomain.h"
 #include "swift/AST/ASTContext.h"
 #include "swift/AST/ASTPrinter.h"
 #include "swift/AST/Decl.h"
@@ -877,6 +878,20 @@ static void formatDiagnosticArgument(StringRef Modifier,
       assert(Modifier.empty() && "Improper modifier for ValueDecl argument");
     }
 
+    // Handle declarations representing an AvailabilityDomain specially.
+    if (auto VD = dyn_cast<ValueDecl>(D)) {
+      if (auto domain = AvailabilityDomain::forCustom(const_cast<ValueDecl *>(VD))) {
+        Out << "availability domain";
+
+        if (includeName) {
+          Out << " " << FormatOpts.OpeningQuotationMark;
+          Out << domain->getNameForDiagnostics();
+          Out << FormatOpts.ClosingQuotationMark;
+        }
+        break;
+      }
+    }
+
     if (includeName) {
       if (auto accessor = dyn_cast<AccessorDecl>(D)) {
         // If it's an accessor, describe that and then switch to discussing its
diff --git a/lib/Sema/MiscDiagnostics.cpp b/lib/Sema/MiscDiagnostics.cpp
index 368f753388b0b..460f489995a4c 100644
--- a/lib/Sema/MiscDiagnostics.cpp
+++ b/lib/Sema/MiscDiagnostics.cpp
@@ -5257,6 +5257,12 @@ static bool diagnoseAvailabilityCondition(PoundAvailableInfo *info,
       return true;
     }
 
+    // Check the availability of the domain decl.
+    if (auto *domainDecl = spec.getDomain().getDecl()) {
+      auto where = ExportContext::forFunctionBody(DC, loc);
+      diagnoseDeclAvailability(domainDecl, loc, nullptr, where);
+    }
+
     hasValidSpecs = true;
     if (!domain.isPlatform())
       allValidSpecsArePlatform = false;
diff --git a/lib/Sema/TypeCheckAccess.cpp b/lib/Sema/TypeCheckAccess.cpp
index b1aae3a489466..bafb1de01e054 100644
--- a/lib/Sema/TypeCheckAccess.cpp
+++ b/lib/Sema/TypeCheckAccess.cpp
@@ -28,6 +28,7 @@
 #include "swift/AST/Import.h"
 #include "swift/AST/ParameterList.h"
 #include "swift/AST/Pattern.h"
+#include "swift/AST/PrettyStackTrace.h"
 #include "swift/AST/TypeCheckRequests.h"
 #include "swift/Basic/Assertions.h"
 #include "clang/AST/DeclCXX.h"
@@ -70,10 +71,22 @@ static void forAllRequirementTypes(
 using CheckTypeAccessCallback =
     void(AccessScope, const TypeRepr *, DowngradeToWarning, ImportAccessLevel);
 
+using CheckDeclAccessCallback = void(AccessScope, SourceLoc, ImportAccessLevel);
+
 class AccessControlCheckerBase {
 protected:
   bool checkUsableFromInline;
 
+  bool shouldSkipChecking(const ValueDecl *decl);
+
+  /// Returns true if access checking ought to be skipped for the given
+  /// `AccessScope`.
+  bool shouldSkipAccessCheckingInContext(AccessScope contextAccessScope,
+                                         const ASTContext &ctx);
+
+  ImportAccessLevel getImportAccessForDecl(const ValueDecl *decl,
+                                           const DeclContext *useDC);
+
   void checkTypeAccessImpl(
       Type type, TypeRepr *typeRepr, AccessScope contextAccessScope,
       const DeclContext *useDC, bool mayBeInferred,
@@ -102,6 +115,12 @@ class AccessControlCheckerBase {
     });
   }
 
+  void checkAvailabilityDomains(const Decl *D);
+
+  void checkDeclAccess(SourceLoc loc, const ValueDecl *decl,
+                       AccessScope contextAccessScope, const DeclContext *useDC,
+                       llvm::function_ref<CheckDeclAccessCallback> diagnose);
+
   AccessControlCheckerBase(bool checkUsableFromInline)
       : checkUsableFromInline(checkUsableFromInline) {}
 
@@ -117,10 +136,50 @@ class AccessControlCheckerBase {
     const ValueDecl *ownerDecl);
 
   void checkGlobalActorAccess(const Decl *D);
+
+  void checkAvailabilityDomains(const Decl *D, AccessScope accessScope,
+                                AccessLevel contextAccess);
 };
 
 } // end anonymous namespace
 
+bool AccessControlCheckerBase::shouldSkipChecking(const ValueDecl *decl) {
+  if (!checkUsableFromInline)
+    return false;
+
+  if (decl->getFormalAccess() != AccessLevel::Internal &&
+      decl->getFormalAccess() != AccessLevel::Package)
+    return true;
+  return !decl->isUsableFromInline();
+}
+
+bool AccessControlCheckerBase::shouldSkipAccessCheckingInContext(
+    AccessScope contextAccessScope, const ASTContext &ctx) {
+  if (ctx.isAccessControlDisabled())
+    return true;
+
+  // Don't spend time checking local declarations; this is always valid by the
+  // time we get to this point.
+  if (contextAccessScope.isInContext() &&
+      contextAccessScope.getDeclContext()->isLocalContext())
+    return true;
+
+  return false;
+}
+
+ImportAccessLevel
+AccessControlCheckerBase::getImportAccessForDecl(const ValueDecl *decl,
+                                                 const DeclContext *useDC) {
+  auto complainImport = decl->getImportAccessFrom(useDC);
+
+  // Don't complain about an import that doesn't restrict the access
+  // level of the decl. This can happen with imported `package` decls.
+  if (complainImport && complainImport->accessLevel >= decl->getFormalAccess())
+    return std::nullopt;
+
+  return complainImport;
+}
+
 /// Searches the given type representation for a `DeclRefTypeRepr` that is
 /// bound to a type declaration with the given access scope. The type
 /// representation is searched in source order. For example, nodes in
@@ -201,12 +260,7 @@ void AccessControlCheckerBase::checkTypeAccessImpl(
     llvm::function_ref<CheckTypeAccessCallback> diagnose) {
 
   auto &Context = useDC->getASTContext();
-  if (Context.isAccessControlDisabled())
-    return;
-  // Don't spend time checking local declarations; this is always valid by the
-  // time we get to this point.
-  if (contextAccessScope.isInContext() &&
-      contextAccessScope.getDeclContext()->isLocalContext())
+  if (shouldSkipAccessCheckingInContext(contextAccessScope, Context))
     return;
 
   // Report where it was imported from.
@@ -229,7 +283,7 @@ void AccessControlCheckerBase::checkTypeAccessImpl(
         return TypeWalker::Action::Continue;
       }));
     }
-  };
+  }
 
   AccessScope problematicAccessScope = AccessScope::getPublic();
 
@@ -307,19 +361,36 @@ void AccessControlCheckerBase::checkTypeAccessImpl(
     const ValueDecl *VD = complainRepr->getBoundDecl();
     assert(VD &&
            "findTypeDeclWithAccessScope should return bound TypeReprs only");
-    complainImport = VD->getImportAccessFrom(useDC);
-
-    // Don't complain about an import that doesn't restrict the access
-    // level of the decl. This can happen with imported `package` decls.
-    if (complainImport.has_value() &&
-        complainImport->accessLevel >= VD->getFormalAccess())
-      complainImport = std::nullopt;
+    complainImport = getImportAccessForDecl(VD, useDC);
   }
 
   diagnose(problematicAccessScope, complainRepr, downgradeToWarning,
            complainImport);
 }
 
+void AccessControlCheckerBase::checkDeclAccess(
+    SourceLoc loc, const ValueDecl *decl, AccessScope contextAccessScope,
+    const DeclContext *useDC,
+    llvm::function_ref<CheckDeclAccessCallback> diagnose) {
+
+  auto &ctx = useDC->getASTContext();
+  if (shouldSkipAccessCheckingInContext(contextAccessScope, ctx))
+    return;
+
+  recordRequiredImportAccessLevelForDecl(
+      decl, useDC, contextAccessScope.accessLevelForDiagnostics(), loc);
+
+  AccessScope declAccessScope =
+      decl->getFormalAccessScope(useDC, checkUsableFromInline);
+  if (contextAccessScope.hasEqualDeclContextWith(declAccessScope) ||
+      contextAccessScope.isChildOf(declAccessScope))
+    return;
+
+  // The reference to the decl violates the rules of access control.
+  ImportAccessLevel complainImport = getImportAccessForDecl(decl, useDC);
+  diagnose(declAccessScope, loc, complainImport);
+}
+
 /// Checks if the access scope of the type described by \p TL is valid for the
 /// type to be the type of \p context. If it isn't, calls \p diagnose with a
 /// TypeRepr representing the offending part of \p TL.
@@ -556,6 +627,50 @@ void AccessControlCheckerBase::checkGlobalActorAccess(const Decl *D) {
       });
 }
 
+void AccessControlCheckerBase::checkAvailabilityDomains(
+    const Decl *D, AccessScope accessScope, AccessLevel contextAccess) {
+  auto &ctx = D->getASTContext();
+  for (auto attr : D->getSemanticAvailableAttrs()) {
+    if (auto *domainDecl = attr.getDomain().getDecl()) {
+      checkDeclAccess(
+          attr.getParsedAttr()->getDomainLoc(), domainDecl, accessScope,
+          D->getDeclContext(),
+          [&](AccessScope domainAccessScope, SourceLoc useLoc,
+              ImportAccessLevel importLimit) {
+            // FIXME: [availability] Improve diagnostics by indicating the decl
+            // that the formal access is implied by. Enum cases, associated
+            // types, protocol requirements, etc. inherit their access level
+            // from their context.
+
+            if (checkUsableFromInline) {
+              ctx.Diags.diagnose(
+                  useLoc, diag::attr_availability_domain_not_usable_from_inline,
+                  attr.getDomain(), attr.getParsedAttr(), D);
+              noteLimitingImport(nullptr, ctx, importLimit, domainDecl);
+              return;
+            }
+
+            ctx.Diags.diagnose(useLoc, diag::attr_availability_domain_access,
+                               attr.getDomain(),
+                               domainAccessScope.accessLevelForDiagnostics(),
+                               attr.getParsedAttr(), contextAccess, D);
+            noteLimitingImport(nullptr, ctx, importLimit, domainDecl);
+          });
+    }
+  }
+}
+
+void AccessControlCheckerBase::checkAvailabilityDomains(const Decl *D) {
+  auto VD = dyn_cast<ValueDecl>(D->getAbstractSyntaxDeclForAttributes());
+  if (!VD || shouldSkipChecking(VD))
+    return;
+
+  AccessScope contextAccessScope =
+      VD->getFormalAccessScope(VD->getDeclContext(), checkUsableFromInline);
+
+  checkAvailabilityDomains(VD, contextAccessScope, VD->getFormalAccess());
+}
+
 namespace {
 class AccessControlChecker : public AccessControlCheckerBase,
                              public DeclVisitor<AccessControlChecker> {
@@ -573,7 +688,7 @@ class AccessControlChecker : public AccessControlCheckerBase,
 
     DeclVisitor<AccessControlChecker>::visit(D);
     checkGlobalActorAccess(D);
-    checkAttachedMacrosAccess(D);
+    checkAvailabilityDomains(D);
   }
 
   // Force all kinds to be handled at a lower level.
@@ -1314,19 +1429,6 @@ class AccessControlChecker : public AccessControlCheckerBase,
       noteLimitingImport(MD, minImportLimit, complainRepr);
     }
   }
-
-  void checkAttachedMacrosAccess(const Decl *D) {
-    for (auto customAttrC : D->getExpandedAttrs().getAttributes<CustomAttr>()) {
-      auto customAttr = const_cast<CustomAttr *>(customAttrC);
-      auto *macroDecl = D->getResolvedMacro(customAttr);
-      if (macroDecl) {
-        diagnoseDeclAvailability(
-            macroDecl, customAttr->getTypeRepr()->getSourceRange(), nullptr,
-            ExportContext::forDeclSignature(const_cast<Decl *>(D)),
-            std::nullopt);
-      }
-    }
-  }
 };
 
 class UsableFromInlineChecker : public AccessControlCheckerBase,
@@ -1335,13 +1437,6 @@ class UsableFromInlineChecker : public AccessControlCheckerBase,
   UsableFromInlineChecker()
       : AccessControlCheckerBase(/*checkUsableFromInline=*/true) {}
 
-  static bool shouldSkipChecking(const ValueDecl *VD) {
-    if (VD->getFormalAccess() != AccessLevel::Internal &&
-        VD->getFormalAccess() != AccessLevel::Package)
-      return true;
-    return !VD->isUsableFromInline();
-  };
-
   void visit(Decl *D) {
     if (!D->getASTContext().isSwiftVersionAtLeast(4, 2))
       return;
@@ -1355,6 +1450,7 @@ class UsableFromInlineChecker : public AccessControlCheckerBase,
 
     DeclVisitor<UsableFromInlineChecker>::visit(D);
     checkGlobalActorAccess(D);
+    checkAvailabilityDomains(D);
   }
 
   // Force all kinds to be handled at a lower level.
@@ -2141,9 +2237,34 @@ class DeclAvailabilityChecker : public DeclVisitor<DeclAvailabilityChecker> {
     checkType(customAttr->getType(), customAttr->getTypeRepr(), D);
   }
 
+  void checkAttachedMacros(const Decl *D) {
+    for (auto customAttrC : D->getExpandedAttrs().getAttributes<CustomAttr>()) {
+      auto customAttr = const_cast<CustomAttr *>(customAttrC);
+      auto *macroDecl = D->getResolvedMacro(customAttr);
+      if (macroDecl) {
+        diagnoseDeclAvailability(macroDecl,
+                                 customAttr->getTypeRepr()->getSourceRange(),
+                                 nullptr, Where, std::nullopt);
+      }
+    }
+  }
+
+  void checkAvailabilityDomains(const Decl *D) {
+    D = D->getAbstractSyntaxDeclForAttributes();
+    for (auto attr : D->getSemanticAvailableAttrs()) {
+      if (auto *domainDecl = attr.getDomain().getDecl()) {
+        diagnoseDeclAvailability(domainDecl,
+                                 attr.getParsedAttr()->getDomainLoc(), nullptr,
+                                 Where, std::nullopt);
+      }
+    }
+  }
+
   void visit(Decl *D) {
     DeclVisitor<DeclAvailabilityChecker>::visit(D);
     checkGlobalActor(D);
+    checkAttachedMacros(D);
+    checkAvailabilityDomains(D);
   }
   
   // Force all kinds to be handled at a lower level.
@@ -2373,14 +2494,10 @@ class DeclAvailabilityChecker : public DeclVisitor<DeclAvailabilityChecker> {
   }
 
   void checkConstrainedExtensionRequirements(ExtensionDecl *ED,
-                                             bool hasExportedMembers) {
+                                             ExportabilityReason reason) {
     if (!ED->getTrailingWhereClause())
       return;
 
-    ExportabilityReason reason =
-        hasExportedMembers ? ExportabilityReason::ExtensionWithPublicMembers
-                           : ExportabilityReason::ExtensionWithConditionalConformances;
-
     forAllRequirementTypes(ED, [&](Type type, TypeRepr *typeRepr) {
       checkType(type, typeRepr, ED, reason,
                 DeclAvailabilityFlag::DisableUnsafeChecking);
@@ -2424,7 +2541,23 @@ class DeclAvailabilityChecker : public DeclVisitor<DeclAvailabilityChecker> {
     // the 'where' clause must only name exported types.
     Where = wasWhere.withExported(hasExportedMembers ||
                                   !ED->getInherited().empty());
-    checkConstrainedExtensionRequirements(ED, hasExportedMembers);
+    ExportabilityReason reason =
+        hasExportedMembers
+            ? ExportabilityReason::ExtensionWithPublicMembers
+            : ExportabilityReason::ExtensionWithConditionalConformances;
+    checkConstrainedExtensionRequirements(ED, reason);
+
+    // Diagnose the exportability of the availability domains referenced by the
+    // @available attributes attached to the extension.
+    if (Where.isExported()) {
+      for (auto availableAttr : ED->getSemanticAvailableAttrs()) {
+        if (auto *domainDecl = availableAttr.getDomain().getDecl()) {
+          TypeChecker::diagnoseDeclRefExportability(
+              availableAttr.getParsedAttr()->getDomainLoc(), domainDecl,
+              Where.withReason(reason));
+        }
+      }
+    }
 
     // If we haven't already visited the extended nominal visit it here.
     // This logic is too wide but prevents false reports of an unused public
@@ -2492,7 +2625,7 @@ class DeclAvailabilityChecker : public DeclVisitor<DeclAvailabilityChecker> {
 
 } // end anonymous namespace
 
-static void checkExtensionGenericParamAccess(const ExtensionDecl *ED) {
+static void checkExtensionAccess(const ExtensionDecl *ED) {
   auto *AA = ED->getAttrs().getAttribute<AccessControlAttr>();
   if (!AA)
     return;
@@ -2523,8 +2656,11 @@ static void checkExtensionGenericParamAccess(const ExtensionDecl *ED) {
     break;
   }
 
-  AccessControlChecker().checkGenericParamAccess(
-      ED, ED, desiredAccessScope, userSpecifiedAccess);
+  auto accessChecker = AccessControlChecker();
+  accessChecker.checkGenericParamAccess(ED, ED, desiredAccessScope,
+                                        userSpecifiedAccess);
+  accessChecker.checkAvailabilityDomains(ED, desiredAccessScope,
+                                         userSpecifiedAccess);
 }
 
 DisallowedOriginKind swift::getDisallowedOriginKind(const Decl *decl,
@@ -2660,13 +2796,10 @@ void swift::checkAccessControl(Decl *D) {
     AccessControlChecker(allowInlineable).visit(D);
     UsableFromInlineChecker().visit(D);
   } else if (auto *ED = dyn_cast<ExtensionDecl>(D)) {
-    checkExtensionGenericParamAccess(ED);
+    checkExtensionAccess(ED);
     registerPackageAccessForPackageExtendedType(ED);
   }
 
-  if (isa<AccessorDecl>(D))
-    return;
-
   auto where = ExportContext::forDeclSignature(D);
   if (where.isImplicit())
     return;
diff --git a/lib/Sema/TypeCheckAttr.cpp b/lib/Sema/TypeCheckAttr.cpp
index 9232601deb7b5..f4a8dae839360 100644
--- a/lib/Sema/TypeCheckAttr.cpp
+++ b/lib/Sema/TypeCheckAttr.cpp
@@ -563,6 +563,9 @@ void AttributeChecker::visitSensitiveAttr(SensitiveAttr *attr) {
 }
 
 void AttributeChecker::visitTransparentAttr(TransparentAttr *attr) {
+  if (attr->isImplicit())
+    return;
+
   DeclContext *dc = D->getDeclContext();
   // Protocol declarations cannot be transparent.
   if (isa<ProtocolDecl>(dc))
diff --git a/lib/Sema/TypeCheckDeclPrimary.cpp b/lib/Sema/TypeCheckDeclPrimary.cpp
index a290483e08c72..f213579f07a17 100644
--- a/lib/Sema/TypeCheckDeclPrimary.cpp
+++ b/lib/Sema/TypeCheckDeclPrimary.cpp
@@ -3719,11 +3719,11 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
         TypeChecker::checkProtocolSelfRequirements(FD);
       }
 
-      checkAccessControl(FD);
-
       TypeChecker::checkParameterList(FD->getParameters(), FD);
     }
 
+    checkAccessControl(FD);
+
     TypeChecker::checkDeclAttributes(FD);
     TypeChecker::checkDistributedFunc(FD);
 
diff --git a/test/ClangImporter/Inputs/availability_domains_bridging_header.h b/test/ClangImporter/Inputs/availability_domains_bridging_header.h
index 18fdfc79293a5..66f8dcf5cb153 100644
--- a/test/ClangImporter/Inputs/availability_domains_bridging_header.h
+++ b/test/ClangImporter/Inputs/availability_domains_bridging_header.h
@@ -1,11 +1,7 @@
-#include <feature-availability.h>
-
-static struct __AvailabilityDomain bay_bridge
-    __attribute__((availability_domain(BayBridge))) = {
-        __AVAILABILITY_DOMAIN_ENABLED, 0};
-static struct __AvailabilityDomain golden_gate_bridge
-    __attribute__((availability_domain(GoldenGateBridge))) = {
-        __AVAILABILITY_DOMAIN_DISABLED, 0};
+#include <availability_domain.h>
+
+CLANG_DISABLED_AVAILABILITY_DOMAIN(BayBridge);
+CLANG_DISABLED_AVAILABILITY_DOMAIN(GoldenGateBridge);
 
 #define AVAIL 0
 #define UNAVAIL 1
diff --git a/test/ClangImporter/access-level-import-availability-custom-domains.swift b/test/ClangImporter/access-level-import-availability-custom-domains.swift
new file mode 100644
index 0000000000000..6963ed1f1532b
--- /dev/null
+++ b/test/ClangImporter/access-level-import-availability-custom-domains.swift
@@ -0,0 +1,328 @@
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -verify \
+// RUN:   -import-objc-header %S/Inputs/availability_domains_bridging_header.h \
+// RUN:   -I %S/../Inputs/custom-modules/availability-domains \
+// RUN:   -enable-experimental-feature CustomAvailability \
+// RUN:   -experimental-spi-only-imports -parse-as-library -swift-version 4 \
+// RUN:   %s
+
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -verify \
+// RUN:   -import-objc-header %S/Inputs/availability_domains_bridging_header.h \
+// RUN:   -I %S/../Inputs/custom-modules/availability-domains \
+// RUN:   -enable-experimental-feature CustomAvailability \
+// RUN:   -experimental-spi-only-imports -parse-as-library -swift-version 5 \
+// RUN:   %s -verify-additional-prefix swift5-
+
+// REQUIRES: swift_feature_CustomAvailability
+
+private import Rivers // also re-exported by Oceans
+internal import Oceans
+// expected-note@-1 22 {{availability domain 'Arctic' imported as 'internal' from 'Oceans' here}}
+// expected-swift5-note@-2 2 {{availability domain 'Arctic' imported as 'internal' from 'Oceans' here}}
+// expected-note@-3 23 {{availability domain 'Colorado' imported as 'internal' from 'Oceans' here}}
+// expected-swift5-note@-4 2 {{availability domain 'Colorado' imported as 'internal' from 'Oceans' here}}
+// expected-note@-5 22 {{availability domain 'Grand' imported as 'internal' from 'Oceans' here}}
+// expected-swift5-note@-6 2 {{availability domain 'Grand' imported as 'internal' from 'Oceans' here}}
+public import Seas
+@_spiOnly import Lakes
+
+@available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public global function 'publicFunc()'}}
+@available(Grand) // expected-error {{availability domain 'Grand' is internal and cannot be used in '@available' on public global function 'publicFunc()'}}
+// expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public global function 'publicFunc()'}}
+@available(Baltic)
+@available(BayBridge)
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+public func publicFunc() { }
+
+@available(Colorado) // expected-swift5-error {{availability domain 'Colorado' used in '@available' on global function 'usableFromInlineFunc()' must be '@usableFromInline' or public}}
+@available(Grand) // expected-swift5-error {{availability domain 'Grand' used in '@available' on global function 'usableFromInlineFunc()' must be '@usableFromInline' or public}}
+// expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic) // expected-swift5-error {{availability domain 'Arctic' used in '@available' on global function 'usableFromInlineFunc()' must be '@usableFromInline' or public}}
+@available(Baltic)
+@available(BayBridge)
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+@usableFromInline func usableFromInlineFunc() { }
+
+@available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public global function 'spiFunc()'}}
+@available(Grand) // expected-error {{availability domain 'Grand' is internal and cannot be used in '@available' on public global function 'spiFunc()'}}
+// expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public global function 'spiFunc()'}}
+@available(Baltic)
+@available(BayBridge)
+@available(Salt)
+@_spi(Private) public func spiFunc() { }
+
+@available(Colorado)
+@available(Grand) // expected-warning {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic)
+@available(Baltic)
+@available(BayBridge)
+@available(Salt)
+func internalFunc() { }
+
+@available(Colorado)
+@available(Grand) // expected-warning {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic)
+@available(Baltic)
+@available(BayBridge)
+@available(Salt)
+private func privateFunc() { }
+
+@available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public var 'publicGlobalVar'}}
+@available(Grand) // expected-error {{availability domain 'Grand' is internal and cannot be used in '@available' on public var 'publicGlobalVar'}}
+// expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public var 'publicGlobalVar'}}
+@available(Baltic)
+@available(BayBridge)
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+public var publicGlobalVar: Int {
+  get { 0 }
+  set { }
+}
+
+@available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public struct 'PublicStruct'}}
+@available(Grand) // expected-error {{availability domain 'Grand' is internal and cannot be used in '@available' on public struct 'PublicStruct'}}
+// expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public struct 'PublicStruct'}}
+@available(Baltic)
+@available(BayBridge)
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+public struct PublicStruct { }
+
+public struct PublicGenericStruct<T> {
+  var value: T
+
+  @available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public initializer 'init(value:)'}}
+  @available(Grand) // expected-error {{availability domain 'Grand' is internal and cannot be used in '@available' on public initializer 'init(value:)'}}
+  // expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+  @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public initializer 'init(value:)'}}
+  @available(Baltic)
+  @available(BayBridge)
+  @available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+  public init(value: T) {
+    self.value = value
+  }
+
+  @available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public property 'publicProperty'}}
+  @available(Grand) // expected-error {{availability domain 'Grand' is internal and cannot be used in '@available' on public property 'publicProperty'}}
+  // expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+  @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public property 'publicProperty'}}
+  @available(Baltic)
+  @available(BayBridge)
+  @available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+  public var publicProperty: T { value }
+
+  @available(Colorado) // expected-swift5-error {{availability domain 'Colorado' used in '@available' on property 'usableFromInlineProperty' must be '@usableFromInline' or public}}
+  @available(Grand) // expected-swift5-error {{availability domain 'Grand' used in '@available' on property 'usableFromInlineProperty' must be '@usableFromInline' or public}}
+  // expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+  @available(Arctic) // expected-swift5-error {{availability domain 'Arctic' used in '@available' on property 'usableFromInlineProperty' must be '@usableFromInline' or public}}
+  @available(Baltic)
+  @available(BayBridge)
+  @available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+  @usableFromInline var usableFromInlineProperty: T { value }
+
+  public var publicPropertyWithSetter: T {
+    get { value }
+
+    @available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public setter for property 'publicPropertyWithSetter'}}
+    @available(Grand) // expected-error {{availability domain 'Grand' is internal and cannot be used in '@available' on public setter for property 'publicPropertyWithSetter'}}
+    // expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+    @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public setter for property 'publicPropertyWithSetter'}}
+    @available(Baltic)
+    @available(BayBridge)
+    @available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+    set { value = newValue }
+  }
+
+  @available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public instance method 'publicMethod()'}}
+  @available(Grand) // expected-error {{availability domain 'Grand' is internal and cannot be used in '@available' on public instance method 'publicMethod()'}}
+  // expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+  @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public instance method 'publicMethod()'}}
+  @available(Baltic)
+  @available(BayBridge)
+  @available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+  public func publicMethod() { }
+
+  @available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public subscript 'subscript(_:)'}}
+  @available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public subscript 'subscript(_:)'}}
+  @available(Grand) // expected-error {{availability domain 'Grand' is internal and cannot be used in '@available' on public subscript 'subscript(_:)'}}
+  // expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+  @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public subscript 'subscript(_:)'}}
+  @available(Baltic)
+  @available(BayBridge)
+  @available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+  public subscript(indexForSubscriptInColorado: T) -> T { value }
+}
+
+@available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public enum 'PublicEnum'}}
+@available(Grand) // expected-error {{availability domain 'Grand' is internal and cannot be used in '@available' on public enum 'PublicEnum'}}
+// expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public enum 'PublicEnum'}}
+@available(Baltic)
+@available(BayBridge)
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+public enum PublicEnum { }
+
+public enum PublicEnumWithCase {
+  @available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public enum case 'colorado'}}
+  @available(Grand) // expected-error {{availability domain 'Grand' is internal and cannot be used in '@available' on public enum case 'colorado'}}
+  // expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+  @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public enum case 'colorado'}}
+  @available(Baltic)
+  @available(BayBridge)
+  @available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+  case colorado
+}
+
+@available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public class 'PublicClass'}}
+@available(Grand) // expected-error {{availability domain 'Grand' is internal and cannot be used in '@available' on public class 'PublicClass'}}
+// expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public class 'PublicClass'}}
+@available(Baltic)
+@available(BayBridge)
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+public class PublicClass { }
+
+@available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public protocol 'PublicProtocol'}}
+@available(Grand) // expected-error {{availability domain 'Grand' is internal and cannot be used in '@available' on public protocol 'PublicProtocol'}}
+// expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public protocol 'PublicProtocol'}}
+@available(Baltic)
+@available(BayBridge)
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+public protocol PublicProtocol { }
+
+public protocol PublicProtocolWithAssociatedType {
+  @available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public associated type 'AssociatedType'}}
+  @available(Grand) // expected-error {{availability domain 'Grand' is internal and cannot be used in '@available' on public associated type 'AssociatedType'}}
+  // expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+  @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public associated type 'AssociatedType'}}
+  @available(Baltic)
+  @available(BayBridge)
+  @available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+  associatedtype AssociatedType
+
+  @available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public instance method 'requirement()'}}
+  @available(Grand) // expected-error {{availability domain 'Grand' is internal and cannot be used in '@available' on public instance method 'requirement()'}}
+  // expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+  @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public instance method 'requirement()'}}
+  @available(Baltic)
+  @available(BayBridge)
+  @available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+  func requirement() -> AssociatedType
+}
+
+@available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public type alias 'PublicTypealias'}}
+@available(Grand) // expected-error {{availability domain 'Grand' is internal and cannot be used in '@available' on public type alias 'PublicTypealias'}}
+// expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public type alias 'PublicTypealias'}}
+@available(Baltic)
+@available(BayBridge)
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+public typealias PublicTypealias = Int
+
+@available(Colorado)
+@available(Grand) // expected-warning {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic)
+@available(Baltic)
+@available(BayBridge)
+@available(Salt)
+extension PublicGenericStruct { }
+
+@available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be used in '@available' on public extension of generic struct 'PublicGenericStruct'}}
+@available(Grand) // expected-error {{availability domain 'Grand' is internal and cannot be used in '@available' on public extension of generic struct 'PublicGenericStruct'}}
+// expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be used in '@available' on public extension of generic struct 'PublicGenericStruct'}}
+@available(Baltic)
+@available(BayBridge)
+@available(Salt) // FIXME: Should be diangosed
+public extension PublicGenericStruct { }
+
+@available(Colorado)
+@available(Grand) // expected-warning {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic)
+@available(Baltic)
+@available(BayBridge)
+@available(Salt)
+extension PublicGenericStruct {
+  func internalMethodInExtensionInColorado() { }
+}
+
+@available(Colorado) // expected-error {{cannot use availability domain 'Colorado' in an extension with public or '@usableFromInline' members; 'Rivers' was not imported publicly}}
+@available(Grand) // expected-error {{cannot use availability domain 'Grand' in an extension with public or '@usableFromInline' members; 'Rivers' was not imported publicly}}
+// expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic) // expected-error {{cannot use availability domain 'Arctic' in an extension with public or '@usableFromInline' members; 'Oceans' was not imported publicly}}
+@available(Baltic)
+@available(BayBridge)
+// FIXME: Duplicate error
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+// expected-error@-1 {{cannot use availability domain 'Salt' in an extension with public or '@usableFromInline' members; 'Lakes' was imported for SPI only}}
+extension PublicGenericStruct {
+  public func publicMethodInExtensionInColorado() { }
+}
+
+@available(Colorado)
+@available(Grand) // expected-warning {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic)
+@available(Baltic)
+@available(BayBridge)
+@available(Salt)
+extension PublicGenericStruct where T: PublicProtocolWithAssociatedType { }
+
+@available(Colorado) // expected-error {{cannot use availability domain 'Colorado' in an extension with conditional conformances; 'Rivers' was not imported publicly}}
+@available(Grand) // expected-error {{cannot use availability domain 'Grand' in an extension with conditional conformances; 'Rivers' was not imported publicly}}
+// expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic) // expected-error {{cannot use availability domain 'Arctic' in an extension with conditional conformances; 'Oceans' was not imported publicly}}
+@available(Baltic)
+@available(BayBridge)
+// FIXME: Duplicate error
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' in an extension with conditional conformances; 'Lakes' was imported for SPI only}}
+// expected-error@-1 {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+extension PublicGenericStruct: PublicProtocol {}
+
+@available(Colorado) // expected-error {{cannot use availability domain 'Colorado' in an extension with public or '@usableFromInline' members; 'Rivers' was not imported publicly}}
+@available(Grand) // expected-error {{cannot use availability domain 'Grand' in an extension with public or '@usableFromInline' members; 'Rivers' was not imported publicly}}
+// expected-warning@-1 {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+@available(Arctic) // expected-error {{cannot use availability domain 'Arctic' in an extension with public or '@usableFromInline' members; 'Oceans' was not imported publicly}}
+@available(Baltic)
+@available(BayBridge)
+// FIXME: Duplicate error
+@available(Salt) // expected-error {{cannot use availability domain 'Salt' here; 'Lakes' was imported for SPI only}}
+// expected-error@-1 {{cannot use availability domain 'Salt' in an extension with public or '@usableFromInline' members; 'Lakes' was imported for SPI only}}
+extension PublicGenericStruct: PublicProtocolWithAssociatedType {
+  public func requirement() -> Int { 0 }
+}
+
+@inlinable public func inlinableFunc() {
+  if #available(Colorado) { } // expected-error {{availability domain 'Colorado' is internal and cannot be referenced from an '@inlinable' function}}
+  if #available(Grand) { } // expected-error {{availability domain 'Grand' is internal and cannot be referenced from an '@inlinable' function}}
+  if #available(Arctic) { } // expected-error {{availability domain 'Arctic' is internal and cannot be referenced from an '@inlinable' function}}
+  if #available(Baltic) { }
+  if #available(BayBridge) { }
+  if #available(Salt) { } // expected-error {{availability domain 'Salt' cannot be used in an '@inlinable' function because 'Lakes' was imported for SPI only}}
+
+  @available(Colorado) // expected-error {{availability domain 'Colorado' is internal and cannot be referenced from an '@inlinable' function}}
+  @available(Grand) // expected-error {{availability domain 'Grand' is internal and cannot be referenced from an '@inlinable' function}}
+  @available(Arctic) // expected-error {{availability domain 'Arctic' is internal and cannot be referenced from an '@inlinable' function}}
+  @available(Baltic)
+  @available(BayBridge)
+  @available(Salt) // expected-error {{availability domain 'Salt' cannot be used in an '@inlinable' function because 'Lakes' was imported for SPI only}}
+  func nestedFunc() { }
+}
+
+public func nonInlinablePublicFunc() {
+  if #available(Colorado) { }
+  if #available(Grand) { } // expected-warning {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+  if #available(Arctic) { }
+  if #available(Baltic) { }
+  if #available(BayBridge) { }
+  if #available(Salt) { }
+
+  @available(Colorado)
+  @available(Grand) // expected-warning {{availability domain 'Grand' is deprecated: Use Colorado instead}}
+  @available(Arctic)
+  @available(Baltic)
+  @available(BayBridge)
+  @available(Salt)
+  func nestedFunc() { }
+}
diff --git a/test/IRGen/Inputs/AvailabilityDomains.h b/test/IRGen/Inputs/AvailabilityDomains.h
index 3248ee721e363..ad923bc48a39b 100644
--- a/test/IRGen/Inputs/AvailabilityDomains.h
+++ b/test/IRGen/Inputs/AvailabilityDomains.h
@@ -1,16 +1,10 @@
-#include <feature-availability.h>
-
-static struct __AvailabilityDomain __EnabledDomain __attribute__((
-    availability_domain(EnabledDomain))) = {__AVAILABILITY_DOMAIN_ENABLED, 0};
-
-static struct __AvailabilityDomain __DisabledDomain __attribute__((
-    availability_domain(DisabledDomain))) = {__AVAILABILITY_DOMAIN_DISABLED, 0};
+#include <availability_domain.h>
 
 int dynamic_domain_pred();
 
-static struct __AvailabilityDomain __DynamicDomain
-    __attribute__((availability_domain(DynamicDomain))) = {
-        __AVAILABILITY_DOMAIN_DYNAMIC, dynamic_domain_pred};
+CLANG_ENABLED_AVAILABILITY_DOMAIN(EnabledDomain);
+CLANG_DISABLED_AVAILABILITY_DOMAIN(DisabledDomain);
+CLANG_DYNAMIC_AVAILABILITY_DOMAIN(DynamicDomain, dynamic_domain_pred);
 
 #define AVAIL 0
 #define UNAVAIL 1
diff --git a/test/Inputs/custom-modules/availability-domains/Lakes.h b/test/Inputs/custom-modules/availability-domains/Lakes.h
new file mode 100644
index 0000000000000..588bd346e965e
--- /dev/null
+++ b/test/Inputs/custom-modules/availability-domains/Lakes.h
@@ -0,0 +1,12 @@
+#include <availability_domain.h>
+
+CLANG_ENABLED_AVAILABILITY_DOMAIN(Salt);
+
+#define AVAIL 0
+#define UNAVAIL 1
+
+__attribute__((availability(domain:Salt, AVAIL)))
+void available_in_salt(void);
+
+#undef UNAVAIL
+#undef AVAIL
diff --git a/test/Inputs/custom-modules/availability-domains/Oceans.h b/test/Inputs/custom-modules/availability-domains/Oceans.h
index d95f5b7d4a18c..57a50b7915a9f 100644
--- a/test/Inputs/custom-modules/availability-domains/Oceans.h
+++ b/test/Inputs/custom-modules/availability-domains/Oceans.h
@@ -1,15 +1,11 @@
 #include <Rivers.h>
-#include <feature-availability.h>
+#include <availability_domain.h>
 
 int arctic_pred(void);
 int pacific_pred(void);
 
-static struct __AvailabilityDomain arctic_domain
-    __attribute__((availability_domain(Arctic))) = {
-        __AVAILABILITY_DOMAIN_DYNAMIC, arctic_pred};
-static struct __AvailabilityDomain pacific_domain
-    __attribute__((availability_domain(Pacific))) = {
-        __AVAILABILITY_DOMAIN_DYNAMIC, pacific_pred};
+CLANG_DYNAMIC_AVAILABILITY_DOMAIN(Arctic, arctic_pred);
+CLANG_DYNAMIC_AVAILABILITY_DOMAIN(Pacific, pacific_pred);
 
 #define AVAIL 0
 #define UNAVAIL 1
diff --git a/test/Inputs/custom-modules/availability-domains/Rivers.h b/test/Inputs/custom-modules/availability-domains/Rivers.h
index 9b026707be742..e36c41d83e001 100644
--- a/test/Inputs/custom-modules/availability-domains/Rivers.h
+++ b/test/Inputs/custom-modules/availability-domains/Rivers.h
@@ -1,7 +1,9 @@
-#include <feature-availability.h>
+#include <availability_domain.h>
 
-static struct __AvailabilityDomain colorado_domain __attribute__((
-    availability_domain(Colorado))) = {__AVAILABILITY_DOMAIN_DISABLED, 0};
+CLANG_DISABLED_AVAILABILITY_DOMAIN(Colorado);
+
+__attribute__((deprecated("Use Colorado instead")))
+CLANG_DISABLED_AVAILABILITY_DOMAIN(Grand);
 
 #define AVAIL 0
 #define UNAVAIL 1
diff --git a/test/Inputs/custom-modules/availability-domains/Seas.h b/test/Inputs/custom-modules/availability-domains/Seas.h
index a5795bb07356c..87541fc7794a0 100644
--- a/test/Inputs/custom-modules/availability-domains/Seas.h
+++ b/test/Inputs/custom-modules/availability-domains/Seas.h
@@ -1,9 +1,7 @@
-#include <feature-availability.h>
+#include <availability_domain.h>
 
-static struct __AvailabilityDomain baltic_domain __attribute__((
-    availability_domain(Baltic))) = {__AVAILABILITY_DOMAIN_ENABLED, 0};
-static struct __AvailabilityDomain _mediterranean __attribute__((
-    availability_domain(Mediterranean))) = {__AVAILABILITY_DOMAIN_ENABLED, 0};
+CLANG_ENABLED_AVAILABILITY_DOMAIN(Baltic);
+CLANG_DISABLED_AVAILABILITY_DOMAIN(Mediterranean);
 
 #define AVAIL 0
 #define UNAVAIL 1
diff --git a/test/Inputs/custom-modules/availability-domains/module.modulemap b/test/Inputs/custom-modules/availability-domains/module.modulemap
index 62930e7c437ab..3d9316f279f71 100644
--- a/test/Inputs/custom-modules/availability-domains/module.modulemap
+++ b/test/Inputs/custom-modules/availability-domains/module.modulemap
@@ -12,3 +12,8 @@ module Seas {
   header "Seas.h"
   export *
 }
+
+module Lakes {
+  header "Lakes.h"
+  export *
+}
diff --git a/test/SILGen/Inputs/AvailabilityDomains.h b/test/SILGen/Inputs/AvailabilityDomains.h
index 213dae3773426..9806517df089d 100644
--- a/test/SILGen/Inputs/AvailabilityDomains.h
+++ b/test/SILGen/Inputs/AvailabilityDomains.h
@@ -1,18 +1,10 @@
-#include <feature-availability.h>
-
-static struct __AvailabilityDomain __EnabledDomain
-    __attribute__((availability_domain(EnabledDomain))) = {
-        __AVAILABILITY_DOMAIN_ENABLED, 0};
-
-static struct __AvailabilityDomain __DisabledDomain
-    __attribute__((availability_domain(DisabledDomain))) = {
-        __AVAILABILITY_DOMAIN_DISABLED, 0};
+#include <availability_domain.h>
 
 int dynamic_domain_pred();
 
-static struct __AvailabilityDomain __DynamicDomain
-    __attribute__((availability_domain(DynamicDomain))) = {
-        __AVAILABILITY_DOMAIN_DYNAMIC, dynamic_domain_pred};
+CLANG_ENABLED_AVAILABILITY_DOMAIN(EnabledDomain);
+CLANG_DISABLED_AVAILABILITY_DOMAIN(DisabledDomain);
+CLANG_DYNAMIC_AVAILABILITY_DOMAIN(DynamicDomain, dynamic_domain_pred);
 
 #define AVAIL 0
 #define UNAVAIL 1