[API Notes] Look for framework API notes in Headers/PrivateHeaders.

Rather than relying on the addition of a new "top-level" directory
within a framework, have frameworks put API notes alongside the
headers.

(cherry picked from commit 1237d45)

Author: DougGregor

lib/APINotes/APINotesManager.cpp

@@ -396,14 +396,20 @@ bool APINotesManager::loadCurrentModuleAPINotes(
     };
 
     if (module->IsFramework) {
-      // For frameworks, we search in the "APINotes" subdirectory.
+      // For frameworks, we search in the "Headers" or "PrivateHeaders"
+      // subdirectory.
       llvm::SmallString<128> path;
       path += module->Directory->getName();
-      llvm::sys::path::append(path, "APINotes");
-      if (auto apinotesDir = fileMgr.getDirectory(path)) {
+      unsigned pathLen = path.size();
+
+      llvm::sys::path::append(path, "Headers");
+      if (auto apinotesDir = fileMgr.getDirectory(path))
         tryAPINotes(apinotesDir, /*wantPublic=*/true);
-        tryAPINotes(apinotesDir, /*wantPublic=*/false);
-      }
+
+      path.resize(pathLen);
+      llvm::sys::path::append(path, "PrivateHeaders");
+      if (auto privateAPINotesDir = fileMgr.getDirectory(path))
+        tryAPINotes(privateAPINotesDir, /*wantPublic=*/false);
     } else {
       tryAPINotes(module->Directory, /*wantPublic=*/true);
       tryAPINotes(module->Directory, /*wantPublic=*/false);

test/APINotes/Inputs/Frameworks/SomeKit.framework/Headers/SomeKit.apinotes

@@ -0,0 +1,42 @@
+Name: SomeKit
+Classes:
+  - Name: A
+    Methods:
+      - Selector:        "transform:"
+        MethodKind:      Instance
+        Availability:    none
+        AvailabilityMsg: "anything but this"
+      - Selector: "transform:integer:"
+        MethodKind:      Instance
+        NullabilityOfRet: N
+        Nullability:      [ N, S ]
+    Properties:
+      - Name: intValue
+        PropertyKind:    Instance
+        Availability: none
+        AvailabilityMsg: "wouldn't work anyway"
+      - Name: nonnullAInstance
+        PropertyKind:    Instance
+        Nullability:     N
+      - Name: nonnullAClass
+        PropertyKind:    Class
+        Nullability:     N
+      - Name: nonnullABoth
+        Nullability:     N
+  - Name: B
+    Availability: none
+    AvailabilityMsg: "just don't"
+  - Name: C
+    Methods:
+      - Selector: "initWithA:"
+        MethodKind: Instance
+        DesignatedInit: true
+SwiftVersions:
+  - Version: 3.0
+    Classes:
+      - Name: A
+        Methods:
+          - Selector: "transform:integer:"
+            MethodKind:      Instance
+            NullabilityOfRet: O
+            Nullability:      [ O, S ]

test/APINotes/Inputs/Frameworks/SomeKit.framework/Headers/SomeKitExplicitNullability.h

@@ -0,0 +1,5 @@
+@interface A(ExplicitNullabilityProperties)
+@property (nonatomic, readwrite, retain, nonnull) A *explicitNonnullInstance;
+@property (nonatomic, readwrite, retain, nullable) A *explicitNullableInstance;
+@end
+

test/APINotes/Inputs/Frameworks/SomeKit.framework/PrivateHeaders/SomeKit_private.apinotes

@@ -0,0 +1,15 @@
+Name: SomeKit
+Classes:
+  - Name: A
+    Methods:         
+      - Selector: "privateTransform:input:"
+        MethodKind:      Instance
+        NullabilityOfRet: N
+        Nullability:      [ N, S ]
+    Properties:
+      - Name: internalProperty
+        Nullability: N
+Protocols:
+  - Name: InternalProtocol
+    Availability: none
+    AvailabilityMsg: "not for you"

test/APINotes/Inputs/Frameworks/SomeOtherKit.framework/Headers/SomeOtherKit.apinotes

@@ -0,0 +1,8 @@
+Name: SomeOtherKit
+Classes:
+  - Name: A
+    Methods:
+      - Selector:        "methodA"
+        MethodKind:      Instance
+        Availability:    none
+        AvailabilityMsg: "anything but this"