diff --git a/CHANGELOG.md b/CHANGELOG.md
index d2bb92dd34743..3ee272369c877 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,33 @@
 
 ## Swift 6.2
 
+* The Swift compiler no longer diagnoses references to declarations that are
+  potentially unavailable because the platform version might not be new enough
+  when those references occur inside of contexts that are also unavailable to
+  that platform. This addresses a long-standing nuisance for multi-platform
+  code. However, there is also a chance that existing source code may become
+  ambiguous as a result:
+
+  ```swift
+  struct A {}
+  struct B {}
+
+  func potentiallyAmbiguous(_: A) {}
+
+  @available(macOS 99, *)
+  func potentiallyAmbiguous(_: B) {}
+
+  @available(macOS, unavailable)
+  func unavailableOnMacOS() {
+    potentiallyAmbiguous(.init()) // error: ambiguous use of 'init()'
+  }
+  ```
+
+  Code that is now ambiguous as a result should likely be restructured since
+  disambiguation based on platform introduction alone has never been a reliable
+  strategy, given that the code would eventually become ambiguous anyways when
+  the deployment target is raised.
+
 * [SE-0419][]:
   Introduced the new `Runtime` module, which contains a public API that can
   generate backtraces, presently supported on macOS and Linux.  Capturing a
diff --git a/lib/AST/AvailabilityConstraint.cpp b/lib/AST/AvailabilityConstraint.cpp
index 9968cdcf2d34a..5377057ad94ec 100644
--- a/lib/AST/AvailabilityConstraint.cpp
+++ b/lib/AST/AvailabilityConstraint.cpp
@@ -113,25 +113,59 @@ DeclAvailabilityConstraints::getPrimaryConstraint() const {
   return result;
 }
 
+static bool canIgnoreConstraintInUnavailableContexts(
+    const Decl *decl, const AvailabilityConstraint &constraint) {
+  auto domain = constraint.getDomain();
+
+  switch (constraint.getReason()) {
+  case AvailabilityConstraint::Reason::UnconditionallyUnavailable:
+    // Always reject uses of universally unavailable declarations, regardless
+    // of context, since there are no possible compilation configurations in
+    // which they are available. However, make an exception for types and
+    // conformances, which can sometimes be awkward to avoid references to.
+    if (!isa<TypeDecl>(decl) && !isa<ExtensionDecl>(decl)) {
+      if (domain.isUniversal() || domain.isSwiftLanguage())
+        return false;
+    }
+    return true;
+
+  case AvailabilityConstraint::Reason::PotentiallyUnavailable:
+    switch (domain.getKind()) {
+    case AvailabilityDomain::Kind::Universal:
+    case AvailabilityDomain::Kind::SwiftLanguage:
+    case AvailabilityDomain::Kind::PackageDescription:
+    case AvailabilityDomain::Kind::Embedded:
+    case AvailabilityDomain::Kind::Custom:
+      return false;
+    case AvailabilityDomain::Kind::Platform:
+      // Platform availability only applies to the target triple that the
+      // binary is being compiled for. Since the same declaration can be
+      // potentially unavailable from a given context when compiling for one
+      // platform, but available from that context when compiling for a
+      // different platform, it is overly strict to enforce potential platform
+      // unavailability constraints in contexts that are unavailable to that
+      // platform.
+      return true;
+    }
+    return constraint.getDomain().isPlatform();
+
+  case AvailabilityConstraint::Reason::Obsoleted:
+  case AvailabilityConstraint::Reason::UnavailableForDeployment:
+    return false;
+  }
+}
+
 static bool
-isInsideCompatibleUnavailableDeclaration(const Decl *decl,
-                                         const SemanticAvailableAttr &attr,
-                                         const AvailabilityContext &context) {
+shouldIgnoreConstraintInContext(const Decl *decl,
+                                const AvailabilityConstraint &constraint,
+                                const AvailabilityContext &context) {
   if (!context.isUnavailable())
     return false;
 
-  if (!attr.isUnconditionallyUnavailable())
+  if (!canIgnoreConstraintInUnavailableContexts(decl, constraint))
     return false;
 
-  // Refuse calling universally unavailable functions from unavailable code,
-  // but allow the use of types.
-  auto domain = attr.getDomain();
-  if (!isa<TypeDecl>(decl) && !isa<ExtensionDecl>(decl)) {
-    if (domain.isUniversal() || domain.isSwiftLanguage())
-      return false;
-  }
-
-  return context.containsUnavailableDomain(domain);
+  return context.containsUnavailableDomain(constraint.getDomain());
 }
 
 /// Returns the `AvailabilityConstraint` that describes how \p attr restricts
@@ -218,8 +252,7 @@ static void getAvailabilityConstraintsForDecl(
   // declaration is unconditionally unavailable in a domain for which
   // the context is already unavailable.
   llvm::erase_if(constraints, [&](const AvailabilityConstraint &constraint) {
-    return isInsideCompatibleUnavailableDeclaration(decl, constraint.getAttr(),
-                                                    context);
+    return shouldIgnoreConstraintInContext(decl, constraint, context);
   });
 }
 
diff --git a/test/Constraints/availability_macos.swift b/test/Constraints/availability_macos.swift
new file mode 100644
index 0000000000000..06e326424ec62
--- /dev/null
+++ b/test/Constraints/availability_macos.swift
@@ -0,0 +1,37 @@
+// RUN: %target-typecheck-verify-swift
+
+// REQUIRES: OS=macosx
+
+struct A {} // expected-note * {{found this candidate}}
+struct B {} // expected-note * {{found this candidate}}
+
+func ambiguousInFarFuture(_: A) {}
+
+@available(macOS 99, *)
+func ambiguousInFarFuture(_: B) {}
+
+struct S {
+  func ambiguousInFarFuture(_: A) {}
+}
+
+@available(macOS 99, *)
+extension S {
+  func ambiguousInFarFuture(_: B) {}
+}
+
+func testDeploymentTarget(_ s: S) {
+  ambiguousInFarFuture(.init())
+  s.ambiguousInFarFuture(.init())
+}
+
+@available(macOS 99, *)
+func testFarFuture(_ s: S) {
+  ambiguousInFarFuture(.init()) // expected-error {{ambiguous use of 'init()'}}
+  s.ambiguousInFarFuture(.init()) // expected-error {{ambiguous use of 'init()'}}
+}
+
+@available(macOS, unavailable)
+func testUnavailable(_ s: S) {
+  ambiguousInFarFuture(.init()) // expected-error {{ambiguous use of 'init()'}}
+  s.ambiguousInFarFuture(.init()) // expected-error {{ambiguous use of 'init()'}}
+}
diff --git a/test/Sema/availability_scopes.swift b/test/Sema/availability_scopes.swift
index b3a3ea56964c1..8042beeb145b2 100644
--- a/test/Sema/availability_scopes.swift
+++ b/test/Sema/availability_scopes.swift
@@ -253,19 +253,19 @@ extension SomeClass {
 
 // CHECK-NEXT: {{^}}  (decl_implicit version=50 decl=extension.SomeClass
 // CHECK-NEXT: {{^}}    (decl version=50 unavailable=macOS decl=extension.SomeClass
-// CHECK-NEXT: {{^}}      (decl version=51 unavailable=macOS decl=functionWithStmtConditionsInUnavailableExt()
+// CHECK-NEXT: {{^}}      (decl version=50 unavailable=macOS decl=functionWithStmtConditionsInUnavailableExt()
 // CHECK-NEXT: {{^}}        (condition_following_availability version=52 unavailable=macOS
 // CHECK-NEXT: {{^}}          (condition_following_availability version=53 unavailable=macOS
 // CHECK-NEXT: {{^}}        (if_then version=53 unavailable=macOS
 // CHECK-NEXT: {{^}}          (condition_following_availability version=54 unavailable=macOS
 // CHECK-NEXT: {{^}}          (if_then version=54 unavailable=macOS
 // CHECK-NEXT: {{^}}            (condition_following_availability version=55 unavailable=macOS
-// CHECK-NEXT: {{^}}            (decl version=55 unavailable=macOS decl=funcInGuardElse()
+// CHECK-NEXT: {{^}}            (decl version=54 unavailable=macOS decl=funcInGuardElse()
 // CHECK-NEXT: {{^}}            (guard_fallthrough version=55 unavailable=macOS
 // CHECK-NEXT: {{^}}              (condition_following_availability version=56 unavailable=macOS
 // CHECK-NEXT: {{^}}              (guard_fallthrough version=56 unavailable=macOS
-// CHECK-NEXT: {{^}}          (decl version=57 unavailable=macOS decl=funcInInnerIfElse()
-// CHECK-NEXT: {{^}}        (decl version=53 unavailable=macOS decl=funcInOuterIfElse()
+// CHECK-NEXT: {{^}}          (decl version=53 unavailable=macOS decl=funcInInnerIfElse()
+// CHECK-NEXT: {{^}}        (decl version=50 unavailable=macOS decl=funcInOuterIfElse()
 @available(OSX, unavailable)
 extension SomeClass {
   @available(OSX 51, *)
@@ -401,7 +401,7 @@ extension SomeEnum {
 // CHECK-NEXT: {{^}}  (decl_implicit version=50 decl=extension.SomeEnum
 // CHECK-NEXT: {{^}}    (decl version=50 unavailable=macOS decl=extension.SomeEnum
 // CHECK-NEXT: {{^}}      (decl_implicit version=50 unavailable=macOS decl=availableMacOS_52
-// CHECK-NEXT: {{^}}        (decl version=52 unavailable=macOS decl=availableMacOS_52
+// CHECK-NEXT: {{^}}        (decl version=50 unavailable=macOS decl=availableMacOS_52
 // CHECK-NEXT: {{^}}      (decl version=50 unavailable=* decl=neverAvailable()
 
 @available(macOS, unavailable)
@@ -418,10 +418,25 @@ extension SomeEnum {
 
 // CHECK-NEXT: {{^}}  (decl version=50 unavailable=macOS decl=unavailableOnMacOSAndIntroduced()
 
-@available(macOS, unavailable, introduced: 52)
+@available(macOS, unavailable)
+@available(macOS, introduced: 52)
 func unavailableOnMacOSAndIntroduced() {
 }
 
+// CHECK-NEXT: {{^}}  (decl version=50 unavailable=macOS decl=introducedOnMacOSAndUnavailable()
+
+@available(macOS, introduced: 53)
+@available(macOS, unavailable)
+func introducedOnMacOSAndUnavailable() {
+}
+
+
+// CHECK-NEXT: {{^}}  (decl version=50 unavailable=macOS decl=unavailableOnMacOSAndIntroducedSameAttr()
+
+@available(macOS, unavailable, introduced: 54)
+func unavailableOnMacOSAndIntroducedSameAttr() {
+}
+
 // CHECK-NEXT: {{^}}  (decl version=50 unavailable=* decl=NeverAvailable
 // CHECK-NEXT: {{^}}    (decl version=50 unavailable=* decl=unavailableOnMacOS()
 
diff --git a/test/Sema/property_wrapper_availability.swift b/test/Sema/property_wrapper_availability.swift
index daf3ab2771322..030be36469e15 100644
--- a/test/Sema/property_wrapper_availability.swift
+++ b/test/Sema/property_wrapper_availability.swift
@@ -99,7 +99,7 @@ struct UnavailableStruct {
   @UnavailableWrapper var unavailableInferred = S()
 
   @WrappedValueUnavailableOnMacOS var unavailableWrappedValue: S
-  @WrappedValueAvailable51 var wrappedValueAavailable51: S // expected-error {{'wrappedValue' is only available in macOS 51 or newer}}
+  @WrappedValueAvailable51 var wrappedValueAavailable51: S
 }
 
 @available(macOS, unavailable)
@@ -117,7 +117,7 @@ struct UnavailableOnMacOSStruct {
   @UnavailableWrapper var unavailableInferred = S()
 
   @WrappedValueUnavailableOnMacOS var unavailableWrappedValue: S
-  @WrappedValueAvailable51 var wrappedValueAavailable51: S // expected-error {{'wrappedValue' is only available in macOS 51 or newer}}
+  @WrappedValueAvailable51 var wrappedValueAavailable51: S
 }
 
 func alwaysAvailableFunc( // expected-note 4 {{add @available attribute to enclosing global function}}
@@ -160,14 +160,14 @@ func unavailableFunc(
   @DeprecatedWrapper _ deprecated: S,
   @UnavailableWrapper _ unavailable: S,
   @WrappedValueUnavailableOnMacOS _ unavailableWrappedValue: S,
-  @WrappedValueAvailable51 _ wrappedValueAavailable51: S // expected-error {{'wrappedValue' is only available in macOS 51 or newer}}
+  @WrappedValueAvailable51 _ wrappedValueAavailable51: S
 ) {
   @AlwaysAvailableWrapper var alwaysAvailableLocal = S()
   @Available51Wrapper var available51Local = S()
   @DeprecatedWrapper var deprecatedLocal = S()
   @UnavailableWrapper var unavailableLocal = S()
   @WrappedValueUnavailableOnMacOS var unavailableWrappedValueLocal = S()
-  @WrappedValueAvailable51 var wrappedValueAavailable51 = S() // expected-error {{'wrappedValue' is only available in macOS 51 or newer}}
+  @WrappedValueAvailable51 var wrappedValueAavailable51 = S()
 }
 
 @available(macOS, unavailable)
@@ -177,12 +177,12 @@ func unavailableOnMacOSFunc(
   @DeprecatedWrapper _ deprecated: S,
   @UnavailableWrapper _ unavailable: S,
   @WrappedValueUnavailableOnMacOS _ unavailableWrappedValue: S,
-  @WrappedValueAvailable51 _ wrappedValueAavailable51: S // expected-error {{'wrappedValue' is only available in macOS 51 or newer}}
+  @WrappedValueAvailable51 _ wrappedValueAavailable51: S
 ) {
   @AlwaysAvailableWrapper var alwaysAvailableLocal = S()
   @Available51Wrapper var available51Local = S()
   @DeprecatedWrapper var deprecatedLocal = S()
   @UnavailableWrapper var unavailableLocal = S()
   @WrappedValueUnavailableOnMacOS var unavailableWrappedValueLocal = S()
-  @WrappedValueAvailable51 var wrappedValueAavailable51 = S() // expected-error {{'wrappedValue' is only available in macOS 51 or newer}}
+  @WrappedValueAvailable51 var wrappedValueAavailable51 = S()
 }
diff --git a/test/attr/attr_availability_transitive_osx.swift b/test/attr/attr_availability_transitive_osx.swift
index b0a17ee2f3b93..7187ca6c26ea0 100644
--- a/test/attr/attr_availability_transitive_osx.swift
+++ b/test/attr/attr_availability_transitive_osx.swift
@@ -87,8 +87,7 @@ func never_available_func(
 ) {
   always()
   never() // expected-error {{'never()' is unavailable}}
-  osx_future() // expected-error {{'osx_future()' is only available in macOS 99 or newer}}
-  // expected-note@-1 {{add 'if #available' version check}}
+  osx_future()
   osx()
   osx_ios()
   osx_extension()
@@ -105,8 +104,7 @@ func osx_func(
 ) {
   always()
   never() // expected-error {{'never()' is unavailable}}
-  osx_future() // expected-error {{'osx_future()' is only available in macOS 99 or newer}}
-  // expected-note@-1 {{add 'if #available' version check}}
+  osx_future()
   osx()
   osx_ios()
   osx_extension()
@@ -159,7 +157,7 @@ var never_var: (
 ) = (
   always(),
   never(), // expected-error {{'never()' is unavailable}}
-  osx_future(), // expected-error {{'osx_future()' is only available in macOS 99 or newer}}
+  osx_future(),
   osx(),
   osx_ios(),
   osx_extension()
@@ -176,7 +174,7 @@ var osx_var: (
 ) = (
   always(),
   never(), // expected-error {{'never()' is unavailable}}
-  osx_future(), // expected-error {{'osx_future()' is only available in macOS 99 or newer}}
+  osx_future(),
   osx(),
   osx_ios(),
   osx_extension()
@@ -218,7 +216,7 @@ struct AlwaysAvailableContainer { // expected-note 2 {{add @available attribute
 struct NeverAvailableContainer { // expected-note 2 {{'NeverAvailableContainer' has been explicitly marked unavailable here}}
   let always_var: AlwaysAvailable = always()
   let never_var: NeverAvailable = never() // expected-error {{'never()' is unavailable}}
-  let osx_future_var: OSXFutureAvailable = osx_future() // expected-error {{'osx_future()' is only available in macOS 99 or newer}}
+  let osx_future_var: OSXFutureAvailable = osx_future()
   let osx_var: OSXUnavailable = osx()
   let osx_ios_var: MultiPlatformUnavailable = osx_ios()
   let osx_extension_var: OSXAppExtensionsUnavailable = osx_extension()
@@ -228,7 +226,7 @@ struct NeverAvailableContainer { // expected-note 2 {{'NeverAvailableContainer'
 struct OSXUnavailableContainer { // expected-note 2 {{'OSXUnavailableContainer' has been explicitly marked unavailable here}}
   let always_var: AlwaysAvailable = always()
   let never_var: NeverAvailable = never() // expected-error {{'never()' is unavailable}}
-  let osx_future_var: OSXFutureAvailable = osx_future() // expected-error {{'osx_future()' is only available in macOS 99 or newer}}
+  let osx_future_var: OSXFutureAvailable = osx_future()
   let osx_var: OSXUnavailable = osx()
   let osx_ios_var: MultiPlatformUnavailable = osx_ios()
   let osx_extension_var: OSXAppExtensionsUnavailable = osx_extension()
@@ -301,8 +299,7 @@ extension ExtendMe {
   ) {
     always()
     never() // expected-error {{'never()' is unavailable}}
-    osx_future() // expected-error {{'osx_future()' is only available in macOS 99 or newer}}
-    // expected-note@-1 {{add 'if #available' version check}}
+    osx_future()
     osx()
     osx_ios()
     osx_extension()
@@ -319,8 +316,7 @@ extension ExtendMe {
   ) {
     always()
     never() // expected-error {{'never()' is unavailable}}
-    osx_future() // expected-error {{'osx_future()' is only available in macOS 99 or newer}}
-    // expected-note@-1 {{add 'if #available' version check}}
+    osx_future()
     osx()
     osx_ios()
     osx_extension()
@@ -337,15 +333,14 @@ extension ExtendMe {
   ) {
     always()
     never() // expected-error {{'never()' is unavailable}}
-    osx_future() // expected-error {{'osx_future()' is only available in macOS 99 or newer}}
-    // expected-note@-1 {{add 'if #available' version check}}
+    osx_future()
     osx()
     osx_ios()
     osx_extension()
   }
 
   @available(OSXApplicationExtension, unavailable)
-  func never_available_extension_osx_app_extension_method( // expected-note {{add @available attribute to enclosing instance method}}
+  func never_available_extension_osx_app_extension_method(
     _: AlwaysAvailable,
     _: NeverAvailable,
     _: OSXFutureAvailable,
@@ -355,8 +350,7 @@ extension ExtendMe {
   ) {
     always()
     never() // expected-error {{'never()' is unavailable}}
-    osx_future() // expected-error {{'osx_future()' is only available in macOS 99 or newer}}
-    // expected-note@-1 {{add 'if #available' version check}}
+    osx_future()
     osx()
     osx_ios()
     osx_extension()
@@ -380,8 +374,7 @@ extension ExtendMe {
   ) {
     always()
     never() // expected-error {{'never()' is unavailable}}
-    osx_future() // expected-error {{'osx_future()' is only available in macOS 99 or newer}}
-    // expected-note@-1 {{add 'if #available' version check}}
+    osx_future()
     osx()
     osx_ios()
     osx_extension()
@@ -398,8 +391,7 @@ extension ExtendMe {
   ) {
     always()
     never() // expected-error {{'never()' is unavailable}}
-    osx_future() // expected-error {{'osx_future()' is only available in macOS 99 or newer}}
-    // expected-note@-1 {{add 'if #available' version check}}
+    osx_future()
     osx()
     osx_ios()
     osx_extension()
@@ -416,15 +408,14 @@ extension ExtendMe {
   ) {
     always()
     never() // expected-error {{'never()' is unavailable}}
-    osx_future() // expected-error {{'osx_future()' is only available in macOS 99 or newer}}
-    // expected-note@-1 {{add 'if #available' version check}}
+    osx_future()
     osx()
     osx_ios()
     osx_extension()
   }
 
   @available(OSXApplicationExtension, unavailable)
-  func osx_extension_osx_app_extension_method( // expected-note {{add @available attribute to enclosing instance method}}
+  func osx_extension_osx_app_extension_method(
     _: AlwaysAvailable,
     _: NeverAvailable,
     _: OSXFutureAvailable,
@@ -434,8 +425,7 @@ extension ExtendMe {
   ) {
     always()
     never() // expected-error {{'never()' is unavailable}}
-    osx_future() // expected-error {{'osx_future()' is only available in macOS 99 or newer}}
-    // expected-note@-1 {{add 'if #available' version check}}
+    osx_future()
     osx()
     osx_ios()
     osx_extension()
@@ -477,8 +467,7 @@ extension ExtendMe { // expected-note * {{add @available attribute to enclosing
   ) {
     always()
     never() // expected-error {{'never()' is unavailable}}
-    osx_future() // expected-error {{'osx_future()' is only available in macOS 99 or newer}}
-    // expected-note@-1 {{add 'if #available' version check}}
+    osx_future()
     osx()
     osx_ios()
     osx_extension()
@@ -495,8 +484,7 @@ extension ExtendMe { // expected-note * {{add @available attribute to enclosing
   ) {
     always()
     never() // expected-error {{'never()' is unavailable}}
-    osx_future() // expected-error {{'osx_future()' is only available in macOS 99 or newer}}
-    // expected-note@-1 {{add 'if #available' version check}}
+    osx_future()
     osx()
     osx_ios()
     osx_extension()
@@ -534,7 +522,7 @@ func available_func_call_extension_methods(_ e: ExtendMe) { // expected-note {{a
 }
 
 @available(OSX, obsoleted: 10.9)
-struct OSXObsoleted {} // expected-note 2 {{'OSXObsoleted' was obsoleted in macOS 10.9}}
+struct OSXObsoleted {} // expected-note 4 {{'OSXObsoleted' was obsoleted in macOS 10.9}}
 
 @available(OSX, unavailable)
 @available(OSX, introduced: 99)
@@ -561,17 +549,46 @@ func osx_unavailable_func(
   OSXUnavailableAndIntroducedInFutureSameAttribute,
   OSXIntroducedInFutureAndUnavailable
 ) {
-  // FIXME: [availability] Stop diagnosing potential unavailability or obsoletion in an unavailable context.
-  _ = OSXFutureAvailable() // expected-error {{'OSXFutureAvailable' is only available in macOS 99 or newer}}
-  // expected-note@-1 {{add 'if #available' version check}}
+  // FIXME: [availability] Stop diagnosing obsoletion in an unavailable context.
+  _ = OSXFutureAvailable()
   _ = OSXObsoleted() // expected-error {{'OSXObsoleted' is unavailable in macOS}}
   _ = OSXUnavailableAndIntroducedInFuture()
   _ = OSXUnavailableAndIntroducedInFutureSameAttribute()
   _ = OSXIntroducedInFutureAndUnavailable()
 
   func takesType<T>(_ t: T.Type) {}
-  takesType(OSXFutureAvailable.self) // expected-error {{'OSXFutureAvailable' is only available in macOS 99 or newer}}
-  // expected-note@-1 {{add 'if #available' version check}}
+  takesType(OSXFutureAvailable.self)
+  takesType(OSXObsoleted.self) // expected-error {{'OSXObsoleted' is unavailable in macOS}}
+  takesType(OSXUnavailableAndIntroducedInFuture.self)
+  takesType(OSXUnavailableAndIntroducedInFutureSameAttribute.self)
+  takesType(OSXIntroducedInFutureAndUnavailable.self)
+
+  return (s1, s2, s3, s4, s5)
+}
+
+@available(OSX, unavailable, introduced: 99)
+func osx_unavailable_and_introduced_func(
+  _ s1: OSXFutureAvailable,
+  _ s2: OSXObsoleted,
+  _ s3: OSXUnavailableAndIntroducedInFuture,
+  _ s4: OSXUnavailableAndIntroducedInFutureSameAttribute,
+  _ s5: OSXIntroducedInFutureAndUnavailable,
+) -> (
+  OSXFutureAvailable,
+  OSXObsoleted,
+  OSXUnavailableAndIntroducedInFuture,
+  OSXUnavailableAndIntroducedInFutureSameAttribute,
+  OSXIntroducedInFutureAndUnavailable
+) {
+  // FIXME: [availability] Stop diagnosing obsoletion in an unavailable context.
+  _ = OSXFutureAvailable()
+  _ = OSXObsoleted() // expected-error {{'OSXObsoleted' is unavailable in macOS}}
+  _ = OSXUnavailableAndIntroducedInFuture()
+  _ = OSXUnavailableAndIntroducedInFutureSameAttribute()
+  _ = OSXIntroducedInFutureAndUnavailable()
+
+  func takesType<T>(_ t: T.Type) {}
+  takesType(OSXFutureAvailable.self)
   takesType(OSXObsoleted.self) // expected-error {{'OSXObsoleted' is unavailable in macOS}}
   takesType(OSXUnavailableAndIntroducedInFuture.self)
   takesType(OSXUnavailableAndIntroducedInFutureSameAttribute.self)
diff --git a/test/attr/attr_availability_transitive_osx_appext.swift b/test/attr/attr_availability_transitive_osx_appext.swift
index 412af439ffe15..371b90cbd5943 100644
--- a/test/attr/attr_availability_transitive_osx_appext.swift
+++ b/test/attr/attr_availability_transitive_osx_appext.swift
@@ -386,8 +386,7 @@ func osx_func_call_extension_methods(_ e: ExtendMe) {
 
   e.never_available_extension_osx_future_method() // expected-error {{'never_available_extension_osx_future_method()' is unavailable}}
   e.osx_extension_osx_future_method()
-  e.osx_app_extension_extension_osx_future_method() // expected-error {{'osx_app_extension_extension_osx_future_method()' is only available in macOS 99 or newer}}
-  // expected-note@-1 {{add 'if #available' version check}}
+  e.osx_app_extension_extension_osx_future_method()
   e.osx_app_extension_extension_never_available_method() // expected-error {{'osx_app_extension_extension_never_available_method()' is unavailable}}
   e.osx_app_extension_extension_osx_method()
   e.osx_app_extension_extension_osx_app_extension_method()
diff --git a/test/attr/attr_inlinable_available.swift b/test/attr/attr_inlinable_available.swift
index 1f948801dc06f..4b6cd0e875a75 100644
--- a/test/attr/attr_inlinable_available.swift
+++ b/test/attr/attr_inlinable_available.swift
@@ -321,14 +321,14 @@ public func alwaysUnavailable(
 ) {
   defer {
     _ = AtDeploymentTarget()
-    _ = AfterDeploymentTarget() // expected-error {{'AfterDeploymentTarget' is only available in macOS 11 or newer}} expected-note {{add 'if #available'}}
+    _ = AfterDeploymentTarget()
   }
   _ = NoAvailable()
   _ = BeforeInliningTarget()
   _ = AtInliningTarget()
   _ = BetweenTargets()
   _ = AtDeploymentTarget()
-  _ = AfterDeploymentTarget() // expected-error {{'AfterDeploymentTarget' is only available in macOS 11 or newer}} expected-note {{add 'if #available'}}
+  _ = AfterDeploymentTarget()
   _ = Unavailable()
   
   if #available(macOS 11, *) {
@@ -568,14 +568,14 @@ public func spiDeployedUseNoAvailable( // expected-note 3 {{add @available attri
 ) {
   defer {
     _ = AtDeploymentTarget()
-    _ = AfterDeploymentTarget() // expected-error {{'AfterDeploymentTarget' is only available in macOS 11 or newer}} expected-note {{add 'if #available'}}
+    _ = AfterDeploymentTarget()
   }
   _ = NoAvailable()
   _ = BeforeInliningTarget()
   _ = AtInliningTarget()
   _ = BetweenTargets()
   _ = AtDeploymentTarget()
-  _ = AfterDeploymentTarget() // expected-error {{'AfterDeploymentTarget' is only available in macOS 11 or newer}} expected-note {{add 'if #available'}}
+  _ = AfterDeploymentTarget()
   _ = Unavailable()
 
   if #available(macOS 11, *) {
@@ -718,7 +718,7 @@ public func spiDeployedUseNoAvailable( // expected-note 3 {{add @available attri
   _ = AtInliningTarget()
   _ = BetweenTargets()
   _ = AtDeploymentTarget()
-  _ = AfterDeploymentTarget() // expected-error {{'AfterDeploymentTarget' is only available in macOS 11 or newer}} expected-note {{add 'if #available'}}
+  _ = AfterDeploymentTarget()
 
   if #available(macOS 11, *) {
     _ = AfterDeploymentTarget()
@@ -727,7 +727,7 @@ public func spiDeployedUseNoAvailable( // expected-note 3 {{add @available attri
   return ()
 }
 
-@inlinable public var inlinedNoAvailableGlobalUnavailableSetter: Any { // expected-note {{add @available attribute to enclosing var}}
+@inlinable public var inlinedNoAvailableGlobalUnavailableSetter: Any {
   get {
     fatalError()
   }
@@ -738,7 +738,7 @@ public func spiDeployedUseNoAvailable( // expected-note 3 {{add @available attri
     _ = AtInliningTarget()
     _ = BetweenTargets()
     _ = AtDeploymentTarget()
-    _ = AfterDeploymentTarget() // expected-error {{'AfterDeploymentTarget' is only available in macOS 11 or newer}} expected-note {{add 'if #available'}}
+    _ = AfterDeploymentTarget()
 
     if #available(macOS 11, *) {
       _ = AfterDeploymentTarget()
@@ -847,7 +847,7 @@ public func defaultArgsUseUnavailable(
   _: Any = AtInliningTarget.self,
   _: Any = BetweenTargets.self,
   _: Any = AtDeploymentTarget.self,
-  _: Any = AfterDeploymentTarget.self, // expected-error {{'AfterDeploymentTarget' is only available in macOS 11 or newer}}
+  _: Any = AfterDeploymentTarget.self,
   _: Any = Unavailable.self
 ) {}
 
@@ -909,7 +909,7 @@ public struct PropertyWrapper<T> {
   public init(_ value: T) { self.wrappedValue = value }
 }
 
-public struct PublicStruct { // expected-note 21 {{add @available attribute}}
+public struct PublicStruct { // expected-note 20 {{add @available attribute}}
   // Public property declarations are exposed.
   public var aPublic: NoAvailable,
              bPublic: BeforeInliningTarget,
@@ -961,7 +961,7 @@ public struct PublicStruct { // expected-note 21 {{add @available attribute}}
 
   @available(macOS, unavailable)
   public var fUnavailable: AfterDeploymentTarget {
-    AfterDeploymentTarget() // expected-error {{'AfterDeploymentTarget' is only available in macOS 11 or newer}} expected-note {{add 'if #available' version check}}
+    AfterDeploymentTarget()
   }
 
   // The inferred types of public properties are exposed.
@@ -1167,7 +1167,7 @@ public struct UnavailablePublicStruct {
              cPublicInit: Any = AtInliningTarget(),
              dPublicInit: Any = BetweenTargets(),
              ePublicInit: Any = AtDeploymentTarget(),
-             fPublicInit: Any = AfterDeploymentTarget(), // expected-error {{'AfterDeploymentTarget' is only available in macOS 11 or newer}}
+             fPublicInit: Any = AfterDeploymentTarget(),
              gPublicInit: Any = Unavailable()
 
   var aInternal: NoAvailable = .init(),