[PrintAsObjC] Silence -Wnullability for the generated declarations. (#10247)

Since Swift 3 and Swift 4 might have different views of an Objective-C
API's nullability, we can end up with incompatible overrides,
including with inherited initializers. This is unfortunate but also
realistic; the Swift 3 code is /not/ set up to handle the new nullability
used by Swift 4 and Objective-C. Just silence the warning.

(It would be nice to not print inherited initializers at all, but that
would mean making sure there are no convenience initializers we have
to print as well. Otherwise the class would get mistaken for one
without explicit designated initializers.)

rdar://problem/32571301

Author: jrose-apple

lib/PrintAsObjC/PrintAsObjC.cpp

@@ -2713,6 +2713,7 @@ class ModuleWriter {
         "# pragma clang diagnostic ignored \"-Wpragma-clang-attribute\"\n"
         "#endif\n"
         "#pragma clang diagnostic ignored \"-Wunknown-pragmas\"\n"
+        "#pragma clang diagnostic ignored \"-Wnullability\"\n"
         "\n"
         "SWIFT_MODULE_NAMESPACE_PUSH(\"" << M.getNameStr() << "\")\n"
       << os.str()

test/PrintAsObjC/Inputs/custom-modules/NestedClass.apinotes

@@ -0,0 +1,24 @@
+Name: VersionedFMWK
+SwiftVersions:
+  - Version: 3.0
+    Classes:
+      - Name: InnerClass
+        SwiftName: InnerClass
+      - Name: NullabilityBase
+        Methods:
+          - Selector: 'initFormerlyFailableValue:'
+            MethodKind: Instance
+            NullabilityOfRet: O
+          - Selector: 'processNowNullableArgument:'
+            MethodKind: Instance
+            Parameters:
+              - Position: 0
+                Nullability: N
+    Tags:
+      - Name: InnerStruct
+        SwiftName: InnerStruct
+    Typedefs:
+      - Name: InnerAlias
+        SwiftName: InnerAlias
+      - Name: InnerAnonStruct
+        SwiftName: InnerAnonStruct

test/PrintAsObjC/Inputs/custom-modules/VersionedFMWK.apinotes

@@ -19,3 +19,8 @@ typedef struct {
 
 typedef int InnerAlias __attribute__((swift_name("Outer.InnerA")));
 
+
+@interface NullabilityBase : NSObject
+- (nonnull instancetype)initFormerlyFailableValue:(NSInteger)value __attribute__((objc_designated_initializer));
+- (void)processNowNullableArgument:(nullable NSObject *)object;
+@end

test/PrintAsObjC/Inputs/custom-modules/NestedClass.h renamed to test/PrintAsObjC/Inputs/custom-modules/VersionedFMWK.h

@@ -38,7 +38,7 @@ module CompatibilityAlias {
   export *
 }
 
-module NestedClass {
-  header "NestedClass.h"
+module VersionedFMWK {
+  header "VersionedFMWK.h"
   export *
 }

test/PrintAsObjC/Inputs/custom-modules/module.map

@@ -14,9 +14,16 @@
 // RUN: %target-swift-frontend(mock-sdk: -sdk %S/../Inputs/clang-importer-sdk -I %t) -parse-as-library %t/versioned.swiftmodule -typecheck -I %S/Inputs/custom-modules -emit-objc-header-path %t/versioned.h -import-objc-header %S/../Inputs/empty.h -disable-objc-attr-requires-foundation-module -swift-version 3
 // RUN: %FileCheck %s < %t/versioned.h
 // RUN: %check-in-clang -I %S/Inputs/custom-modules/ %t/versioned.h
-// RUN: %check-in-clang -I %S/Inputs/custom-modules/ -fno-modules -Qunused-arguments %t/versioned.h -include Foundation.h -include NestedClass.h
+// RUN: %check-in-clang -I %S/Inputs/custom-modules/ -fno-modules -Qunused-arguments %t/versioned.h -include Foundation.h -include VersionedFMWK.h
 
-import NestedClass
+import VersionedFMWK
+
+// CHECK-LABEL: @interface NullabilitySub
+@objc class NullabilitySub: NullabilityBase {
+  // CHECK-NEXT: - (void)processNowNullableArgument:(NSObject * _Nonnull)object;
+  override func processNowNullableArgument(_ object: NSObject) {}
+  // CHECK-NEXT: - (nullable instancetype)initFormerlyFailableValue:(NSInteger)value OBJC_DESIGNATED_INITIALIZER;
+} // CHECK-NEXT: @end
 
 // CHECK-LABEL: @interface UsesNestedClass
 @objc class UsesNestedClass : NSObject {