AST: Check the availability context from Decl::isWeakImported()

Fixes <rdar://problem/46674512>.

Author: slavapestov

lib/AST/Decl.cpp

@@ -547,6 +547,11 @@ bool Decl::isWeakImported(ModuleDecl *fromModule,
   if (containingModule == fromModule)
     return false;
 
+  auto containingContext =
+      AvailabilityInference::availableRange(this, fromModule->getASTContext());
+  if (!fromContext.isContainedIn(containingContext))
+    return true;
+
   if (getAttrs().hasAttribute<WeakLinkedAttr>())
     return true;
 
@@ -563,7 +568,6 @@ bool Decl::isWeakImported(ModuleDecl *fromModule,
   if (auto *ntd = dyn_cast<NominalTypeDecl>(dc))
     return ntd->isWeakImported(fromModule, fromContext);
 
-  // FIXME: Also check availability when containingModule is resilient.
   return false;
 }
 

test/IRGen/Inputs/weak_import_availability_helper.swift

@@ -0,0 +1,27 @@
+@available(macOS 10.50, *)
+public func conditionallyAvailableFunction() {}
+
+@available(macOS 10.50, *)
+public var conditionallyAvailableGlobal: Int {
+  get {return 0}
+  set {}
+}
+
+@available(macOS 10.50, *)
+public struct ConditionallyAvailableStruct {
+  public func conditionallyAvailableMethod() {}
+}
+
+public protocol AlwaysAvailableProtocol {}
+
+public struct AlwaysAvailableStruct {}
+
+@available(macOS 10.50, *)
+extension AlwaysAvailableStruct : AlwaysAvailableProtocol {}
+
+public enum AlwaysAvailableEnum {
+  case alwaysAvailableCase
+
+  @available(macOS 10.50, *)
+  case conditionallyAvailableCase
+}

test/IRGen/weak_import_availability.swift

@@ -0,0 +1,63 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -emit-module -emit-module-path %t/weak_import_availability_helper.swiftmodule -parse-as-library %S/Inputs/weak_import_availability_helper.swift -enable-resilience
+//
+// RUN: %target-swift-frontend -primary-file %s -I %t -emit-ir | %FileCheck %s
+
+// REQUIRES: OS=macosx
+
+import weak_import_availability_helper
+
+public func useConditionallyAvailableCase(e: AlwaysAvailableEnum) {
+  switch e {
+    case .alwaysAvailableCase: break
+    case .conditionallyAvailableCase: break
+  }
+}
+
+// CHECK-LABEL: @"$s31weak_import_availability_helper19AlwaysAvailableEnumO013conditionallyF4CaseyA2CmFWC" = extern_weak constant i32
+
+func useConformance<T : AlwaysAvailableProtocol>(_: T.Type) {}
+
+@available(macOS 10.50, *)
+public func useConditionallyAvailableConformance() {
+  useConformance(AlwaysAvailableStruct.self)
+}
+
+// FIXME: We reference the witness table directly -- that's a bug since the module is resilient. Should reference the
+// conformance descriptor instead.
+
+// CHECK-LABEL: @"$s31weak_import_availability_helper21AlwaysAvailableStructVAA0eF8ProtocolAAWP" = extern_weak global i8*
+
+@available(macOS 10.50, *)
+public func callConditionallyAvailableFunction() {
+  conditionallyAvailableFunction()
+}
+
+// CHECK-LABEL: declare extern_weak swiftcc void @"$s31weak_import_availability_helper30conditionallyAvailableFunctionyyF"()
+
+@available(macOS 10.50, *)
+public func useConditionallyAvailableGlobal() {
+  _ = conditionallyAvailableGlobal
+  conditionallyAvailableGlobal = 0
+  conditionallyAvailableGlobal += 1
+}
+
+// CHECK-LABEL: declare extern_weak swiftcc i64 @"$s31weak_import_availability_helper28conditionallyAvailableGlobalSivg"()
+
+// CHECK-LABEL: declare extern_weak swiftcc void @"$s31weak_import_availability_helper28conditionallyAvailableGlobalSivs"(i64)
+
+func blackHole<T>(_: T) {}
+
+@available(macOS 10.50, *)
+public func useConditionallyAvailableStruct() {
+  blackHole(ConditionallyAvailableStruct.self)
+}
+
+// CHECK-LABEL: declare extern_weak swiftcc %swift.metadata_response @"$s31weak_import_availability_helper28ConditionallyAvailableStructVMa"(i64)
+
+@available(macOS 10.50, *)
+public func useConditionallyAvailableMethod(s: ConditionallyAvailableStruct) {
+  s.conditionallyAvailableMethod()
+}
+
+// CHECK-LABEL: declare extern_weak swiftcc void @"$s31weak_import_availability_helper28ConditionallyAvailableStructV013conditionallyF6MethodyyF"(%swift.opaque* noalias nocapture swiftself)

test/IRGen/weak_import_native.swift

@@ -1,5 +1,5 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-swift-frontend -emit-module -emit-module-path %t/weak_import_native_helper.swiftmodule %S/Inputs/weak_import_native_helper.swift -enable-resilience
+// RUN: %target-swift-frontend -emit-module -emit-module-path %t/weak_import_native_helper.swiftmodule -parse-as-library %S/Inputs/weak_import_native_helper.swift -enable-resilience
 //
 // RUN: %target-swift-frontend -primary-file %s -I %t -emit-ir | %FileCheck %s