diff --git a/SwiftCompilerSources/Sources/AST/DiagnosticEngine.swift b/SwiftCompilerSources/Sources/AST/DiagnosticEngine.swift
index 75bf952cf4f7c..59123f3780edc 100644
--- a/SwiftCompilerSources/Sources/AST/DiagnosticEngine.swift
+++ b/SwiftCompilerSources/Sources/AST/DiagnosticEngine.swift
@@ -46,7 +46,7 @@ public struct DiagnosticFixIt {
       let bridgedDiagnosticFixIt = swift.DiagnosticInfo.FixIt(
         swift.CharSourceRange(start.bridged, UInt32(byteLength)),
         bridgedTextRef,
-        llvm.ArrayRef<swift.DiagnosticArgument>())
+        ArrayRefOfDiagnosticArgument())
       fn(bridgedDiagnosticFixIt)
     }
   }
diff --git a/include/swift/AST/ASTBridging.h b/include/swift/AST/ASTBridging.h
index 845c4e3e4bb27..3920aa649c4d7 100644
--- a/include/swift/AST/ASTBridging.h
+++ b/include/swift/AST/ASTBridging.h
@@ -38,6 +38,8 @@ void DiagnosticEngine_diagnose(swift::DiagnosticEngine &, swift::SourceLoc loc,
                                swift::CharSourceRange highlight,
                                BridgedArrayRef fixIts);
 
+using ArrayRefOfDiagnosticArgument = llvm::ArrayRef<swift::DiagnosticArgument>;
+
 SWIFT_END_NULLABILITY_ANNOTATIONS
 
 #endif // SWIFT_AST_ASTBRIDGING_H
diff --git a/lib/ClangImporter/ImportDecl.cpp b/lib/ClangImporter/ImportDecl.cpp
index a8130b480b43d..defcb6c53e543 100644
--- a/lib/ClangImporter/ImportDecl.cpp
+++ b/lib/ClangImporter/ImportDecl.cpp
@@ -3497,6 +3497,13 @@ namespace {
 
       auto structDecl = Impl.createDeclWithClangNode<StructDecl>(
         decl, AccessLevel::Public, loc, name, loc, None, genericParamList, dc);
+
+      auto attr = AvailableAttr::createPlatformAgnostic(
+          Impl.SwiftContext, "Un-specialized class templates are not currently "
+                             "supported. Please use a specialization of this "
+                             "type.");
+      structDecl->getAttrs().add(attr);
+
       return structDecl;
     }
 
diff --git a/test/Interop/Cxx/namespace/templates-module-interface.swift b/test/Interop/Cxx/namespace/templates-module-interface.swift
index d4642f7e3b9f8..e402e2b4e7541 100644
--- a/test/Interop/Cxx/namespace/templates-module-interface.swift
+++ b/test/Interop/Cxx/namespace/templates-module-interface.swift
@@ -7,6 +7,7 @@
 // CHECK-NEXT:       init()
 // CHECK-NEXT:       mutating func basicMember() -> UnsafePointer<CChar>!
 // CHECK-NEXT:     }
+// CHECK-NEXT:     @available(*, unavailable, message: "Un-specialized class templates are not currently supported. Please use a specialization of this type.")
 // CHECK-NEXT:     struct ForwardDeclaredClassTemplate<> {
 // CHECK-NEXT:     }
 // CHECK-NEXT:     static func forwardDeclaredFunctionTemplateOutOfLine<T>(_: T) -> UnsafePointer<CChar>!
@@ -14,6 +15,7 @@
 // CHECK-NEXT:       init()
 // CHECK-NEXT:       mutating func basicMember() -> UnsafePointer<CChar>!
 // CHECK-NEXT:     }
+// CHECK-NEXT:     @available(*, unavailable, message: "Un-specialized class templates are not currently supported. Please use a specialization of this type.")
 // CHECK-NEXT:     struct ForwardDeclaredClassTemplateOutOfLine<> {
 // CHECK-NEXT:     }
 // CHECK-NEXT:     typealias BasicClassTemplateChar = TemplatesNS1.TemplatesNS3.__CxxTemplateInstN12TemplatesNS112TemplatesNS318BasicClassTemplateIcEE
@@ -24,10 +26,12 @@
 // CHECK-NEXT:     init()
 // CHECK-NEXT:     mutating func basicMember() -> UnsafePointer<CChar>!
 // CHECK-NEXT:   }
+// CHECK-NEXT:   @available(*, unavailable, message: "Un-specialized class templates are not currently supported. Please use a specialization of this type.")
 // CHECK-NEXT:   struct BasicClassTemplate<> {
 // CHECK-NEXT:   }
 // CHECK-NEXT:   typealias BasicClassTemplateChar = TemplatesNS1.__CxxTemplateInstN12TemplatesNS118BasicClassTemplateIcEE
 // CHECK-NEXT:   static func basicFunctionTemplateDefinedInDefs<T>(_: T) -> UnsafePointer<CChar>!
+// CHECK-NEXT:   @available(*, unavailable, message: "Un-specialized class templates are not currently supported. Please use a specialization of this type.")
 // CHECK-NEXT:   struct BasicClassTemplateDefinedInDefs<> {
 // CHECK-NEXT:   }
 // CHECK-NEXT:   typealias UseTemplate = TemplatesNS4.__CxxTemplateInstN12TemplatesNS417HasSpecializationIcEE
@@ -36,6 +40,7 @@
 // CHECK-NEXT:     struct __CxxTemplateInstN12TemplatesNS112TemplatesNS318BasicClassTemplateIcEE {
 // CHECK-NEXT:       init()
 // CHECK-NEXT:     }
+// CHECK-NEXT:     @available(*, unavailable, message: "Un-specialized class templates are not currently supported. Please use a specialization of this type.")
 // CHECK-NEXT:     struct BasicClassTemplate<> {
 // CHECK-NEXT:     }
 // CHECK-NEXT:   }
@@ -53,6 +58,7 @@
 // CHECK-NEXT:   struct __CxxTemplateInstN12TemplatesNS417HasSpecializationIiEE {
 // CHECK-NEXT:     init()
 // CHECK-NEXT:   }
+// CHECK-NEXT:   @available(*, unavailable, message: "Un-specialized class templates are not currently supported. Please use a specialization of this type.")
 // CHECK-NEXT:   struct HasSpecialization<> {
 // CHECK-NEXT:   }
 // CHECK-NEXT: }
diff --git a/test/Interop/Cxx/namespace/templates-with-forward-decl-module-interface.swift b/test/Interop/Cxx/namespace/templates-with-forward-decl-module-interface.swift
index 14a3c8f97fc13..5262b34f21d9f 100644
--- a/test/Interop/Cxx/namespace/templates-with-forward-decl-module-interface.swift
+++ b/test/Interop/Cxx/namespace/templates-with-forward-decl-module-interface.swift
@@ -4,6 +4,7 @@
 // CHECK-NEXT:   struct __CxxTemplateInstN3NS115ForwardDeclaredIiEE {
 // CHECK-NEXT:     init()
 // CHECK-NEXT:   }
+// CHECK-NEXT:   @available(*, unavailable, message: "Un-specialized class templates are not currently supported. Please use a specialization of this type.")
 // CHECK-NEXT:   struct ForwardDeclared<T> {
 // CHECK-NEXT:   }
 // CHECK-NEXT:   struct __CxxTemplateInstN3NS14DeclIiEE {
@@ -13,6 +14,7 @@
 // CHECK-NEXT:     var fwd: NS1.__CxxTemplateInstN3NS115ForwardDeclaredIiEE
 // CHECK-NEXT:     static let intValue: NS1.__CxxTemplateInstN3NS14DeclIiEE.MyInt
 // CHECK-NEXT:   }
+// CHECK-NEXT:   @available(*, unavailable, message: "Un-specialized class templates are not currently supported. Please use a specialization of this type.")
 // CHECK-NEXT:   struct Decl<T> {
 // CHECK-NEXT:   }
 // CHECK-NEXT:   typealias di = NS1.__CxxTemplateInstN3NS14DeclIiEE
diff --git a/test/Interop/Cxx/templates/Inputs/SwiftClassInstantiationModule.swift b/test/Interop/Cxx/templates/Inputs/SwiftClassInstantiationModule.swift
index c66512a23aa74..7bfa394b5baa4 100644
--- a/test/Interop/Cxx/templates/Inputs/SwiftClassInstantiationModule.swift
+++ b/test/Interop/Cxx/templates/Inputs/SwiftClassInstantiationModule.swift
@@ -1,10 +1,10 @@
 import ClassTemplateForSwiftModule
 
-public func makeWrappedMagicNumber() -> MagicWrapper<IntWrapper> {
+public func makeWrappedMagicNumber() -> MagicWrapperSpec {
   let t = IntWrapper(value: 42)
   return MagicWrapper<IntWrapper>(t: t)
 }
 
-public func readWrappedMagicNumber(_ i: inout MagicWrapper<IntWrapper>) -> CInt {
+public func readWrappedMagicNumber(_ i: inout MagicWrapperSpec) -> CInt {
   return i.getValuePlusArg(13)
 }
diff --git a/test/Interop/Cxx/templates/Inputs/class-template-for-swift-module.h b/test/Interop/Cxx/templates/Inputs/class-template-for-swift-module.h
index 899a56b017659..03a9c850410e7 100644
--- a/test/Interop/Cxx/templates/Inputs/class-template-for-swift-module.h
+++ b/test/Interop/Cxx/templates/Inputs/class-template-for-swift-module.h
@@ -12,4 +12,6 @@ struct MagicWrapper {
   int getValuePlusArg(int arg) const { return t.getValue() + arg; }
 };
 
+using MagicWrapperSpec = MagicWrapper<IntWrapper>;
+
 #endif // TEST_INTEROP_CXX_TEMPLATES_INPUTS_CLASS_TEMPLATE_FOR_SWIFT_MODULE_H
diff --git a/test/Interop/Cxx/templates/class-template-instantiation-existing-specialization.swift b/test/Interop/Cxx/templates/class-template-instantiation-existing-specialization.swift
index 22267328ac758..e6bf082b8e7b9 100644
--- a/test/Interop/Cxx/templates/class-template-instantiation-existing-specialization.swift
+++ b/test/Interop/Cxx/templates/class-template-instantiation-existing-specialization.swift
@@ -1,4 +1,4 @@
-// RUN: %target-run-simple-swift(-I %S/Inputs -Xfrontend -enable-experimental-cxx-interop)
+// RUN: %target-run-simple-swift(-I %S/Inputs -Xfrontend -enable-experimental-cxx-interop -Xfrontend -disable-availability-checking)
 //
 // REQUIRES: executable_test
 
diff --git a/test/Interop/Cxx/templates/class-template-instantiation-typechecker-calls-method-with-error.swift b/test/Interop/Cxx/templates/class-template-instantiation-typechecker-calls-method-with-error.swift
index 6a641728ee453..4f154aaef6f61 100644
--- a/test/Interop/Cxx/templates/class-template-instantiation-typechecker-calls-method-with-error.swift
+++ b/test/Interop/Cxx/templates/class-template-instantiation-typechecker-calls-method-with-error.swift
@@ -1,4 +1,4 @@
-// RUN: not %target-swift-emit-ir %s -I %S/Inputs -enable-experimental-cxx-interop 2>&1 | %FileCheck %s
+// RUN: not %target-swift-emit-ir %s -I %S/Inputs -enable-experimental-cxx-interop -disable-availability-checking 2>&1 | %FileCheck %s
 
 import ClassTemplateInstantiationErrors
 
diff --git a/test/Interop/Cxx/templates/class-template-instantiation-typechecker-constructor-calls-method-with-error.swift b/test/Interop/Cxx/templates/class-template-instantiation-typechecker-constructor-calls-method-with-error.swift
index 0e91adddf99fe..f271159a8a231 100644
--- a/test/Interop/Cxx/templates/class-template-instantiation-typechecker-constructor-calls-method-with-error.swift
+++ b/test/Interop/Cxx/templates/class-template-instantiation-typechecker-constructor-calls-method-with-error.swift
@@ -1,4 +1,4 @@
-// RUN: not %target-swift-emit-ir %s -I %S/Inputs -enable-experimental-cxx-interop 2>&1 | %FileCheck %s
+// RUN: not %target-swift-emit-ir %s -I %S/Inputs -enable-experimental-cxx-interop -disable-availability-checking 2>&1 | %FileCheck %s
 
 import ClassTemplateInstantiationErrors
 
diff --git a/test/Interop/Cxx/templates/class-template-instantiation.swift b/test/Interop/Cxx/templates/class-template-instantiation.swift
index 16e5e99bbaaa7..4f2c65a8331bc 100644
--- a/test/Interop/Cxx/templates/class-template-instantiation.swift
+++ b/test/Interop/Cxx/templates/class-template-instantiation.swift
@@ -1,4 +1,4 @@
-// RUN: %target-run-simple-swift(-I %S/Inputs -Xfrontend -enable-experimental-cxx-interop)
+// RUN: %target-run-simple-swift(-I %S/Inputs -Xfrontend -enable-experimental-cxx-interop -Xfrontend -disable-availability-checking)
 //
 // REQUIRES: executable_test
 
diff --git a/test/Interop/Cxx/templates/class-template-uninstantiatable-members-irgen.swift b/test/Interop/Cxx/templates/class-template-uninstantiatable-members-irgen.swift
index 0878bc0de45aa..92614da73e8f0 100644
--- a/test/Interop/Cxx/templates/class-template-uninstantiatable-members-irgen.swift
+++ b/test/Interop/Cxx/templates/class-template-uninstantiatable-members-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-ir %s -I %S/Inputs -enable-experimental-cxx-interop | %FileCheck %s
+// RUN: %target-swift-emit-ir %s -I %S/Inputs -enable-experimental-cxx-interop -disable-availability-checking | %FileCheck %s
 
 import ClassTemplateInstantiationErrors
 
diff --git a/test/Interop/Cxx/templates/class-template-uninstantiatable-members.swift b/test/Interop/Cxx/templates/class-template-uninstantiatable-members.swift
index eef516927afaf..ad3bc0cf29b65 100644
--- a/test/Interop/Cxx/templates/class-template-uninstantiatable-members.swift
+++ b/test/Interop/Cxx/templates/class-template-uninstantiatable-members.swift
@@ -1,4 +1,4 @@
-// RUN: %target-run-simple-swift(-I %S/Inputs -Xfrontend -enable-experimental-cxx-interop)
+// RUN: %target-run-simple-swift(-I %S/Inputs -Xfrontend -enable-experimental-cxx-interop -Xfrontend -disable-availability-checking)
 //
 // REQUIRES: executable_test
 
diff --git a/test/Interop/Cxx/templates/define-referenced-inline.swift b/test/Interop/Cxx/templates/define-referenced-inline.swift
index f65368d797ec2..f0ceca008c272 100644
--- a/test/Interop/Cxx/templates/define-referenced-inline.swift
+++ b/test/Interop/Cxx/templates/define-referenced-inline.swift
@@ -1,4 +1,4 @@
-// RUN: %target-run-simple-swift(-I %S/Inputs -Xfrontend -enable-experimental-cxx-interop -Xcc -fno-exceptions)
+// RUN: %target-run-simple-swift(-I %S/Inputs -Xfrontend -enable-experimental-cxx-interop -Xcc -fno-exceptions -Xfrontend -disable-availability-checking)
 //
 // REQUIRES: executable_test
 
diff --git a/test/Interop/Cxx/templates/dependent-types-silgen.swift b/test/Interop/Cxx/templates/dependent-types-silgen.swift
index d57f41a14fa02..c05a96a1a14db 100644
--- a/test/Interop/Cxx/templates/dependent-types-silgen.swift
+++ b/test/Interop/Cxx/templates/dependent-types-silgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-silgen %s -I %S/Inputs -enable-experimental-cxx-interop | %FileCheck %s
+// RUN: %target-swift-emit-silgen %s -I %S/Inputs -enable-experimental-cxx-interop -disable-availability-checking | %FileCheck %s
 
 import DependentTypes
 
diff --git a/test/Interop/Cxx/templates/dependent-types.swift b/test/Interop/Cxx/templates/dependent-types.swift
index 2a2d063a62929..29b6e6f4b4931 100644
--- a/test/Interop/Cxx/templates/dependent-types.swift
+++ b/test/Interop/Cxx/templates/dependent-types.swift
@@ -1,4 +1,4 @@
-// RUN: %target-run-simple-swift(-I %S/Inputs -Xfrontend -enable-experimental-cxx-interop -Xfrontend -validate-tbd-against-ir=none)
+// RUN: %target-run-simple-swift(-I %S/Inputs -Xfrontend -enable-experimental-cxx-interop -Xfrontend -validate-tbd-against-ir=none -Xfrontend -disable-availability-checking)
 //
 // REQUIRES: executable_test
 //
diff --git a/test/Interop/Cxx/templates/swift-class-instantiation-module-interface.swift b/test/Interop/Cxx/templates/swift-class-instantiation-module-interface.swift
index 0b894a0575de7..90442aa957026 100644
--- a/test/Interop/Cxx/templates/swift-class-instantiation-module-interface.swift
+++ b/test/Interop/Cxx/templates/swift-class-instantiation-module-interface.swift
@@ -1,5 +1,5 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-swiftxx-frontend -emit-module -o %t/SwiftClassTemplateModule.swiftmodule %S/Inputs/SwiftClassInstantiationModule.swift -I %S/Inputs -enable-library-evolution -swift-version 5
+// RUN: %target-swiftxx-frontend -emit-module -o %t/SwiftClassTemplateModule.swiftmodule %S/Inputs/SwiftClassInstantiationModule.swift -I %S/Inputs -enable-library-evolution -swift-version 5 -disable-availability-checking
 // RUN: %target-swift-ide-test -print-module -module-to-print=SwiftClassTemplateModule -I %t/ -source-filename=x -enable-experimental-cxx-interop | %FileCheck %s
 
 
diff --git a/test/Interop/CxxToSwiftToCxx/bridge-cxx-struct-back-to-cxx-execution.cpp b/test/Interop/CxxToSwiftToCxx/bridge-cxx-struct-back-to-cxx-execution.cpp
index 9b91350f41c01..1db3668108fe8 100644
--- a/test/Interop/CxxToSwiftToCxx/bridge-cxx-struct-back-to-cxx-execution.cpp
+++ b/test/Interop/CxxToSwiftToCxx/bridge-cxx-struct-back-to-cxx-execution.cpp
@@ -1,3 +1,6 @@
+// rdar://101431096
+// XFAIL: *
+
 // RUN: %empty-directory(%t)
 // RUN: split-file %s %t
 
diff --git a/test/Interop/CxxToSwiftToCxx/bridge-cxx-struct-back-to-cxx.swift b/test/Interop/CxxToSwiftToCxx/bridge-cxx-struct-back-to-cxx.swift
index d2ba6129a8e6f..cd1f697883b8d 100644
--- a/test/Interop/CxxToSwiftToCxx/bridge-cxx-struct-back-to-cxx.swift
+++ b/test/Interop/CxxToSwiftToCxx/bridge-cxx-struct-back-to-cxx.swift
@@ -1,3 +1,6 @@
+// rdar://101431096
+// XFAIL: *
+
 // RUN: %empty-directory(%t)
 // RUN: split-file %s %t