[ios, macos] Make Xcode 7.3 the minimum required version

- Removes nullability shims for Xcode 6.
- Removes MGLTypes.h from files where it was only being used for
  nullability support.
- Accepts that `NS_SWIFT_NAME` is not fully supported by Xcode 7.2 and
  lower.
- Adds documentation about Xcode 7.3 requirement.

6 files changed, 6 insertions, 8 deletions

diff --git a/platform/macos/DEVELOPING.md b/platform/macos/DEVELOPING.md
index 5f437f4172..412a58a140 100644
--- a/platform/macos/DEVELOPING.md
+++ b/platform/macos/DEVELOPING.md
@@ -4,7 +4,9 @@ This document explains how to build the Mapbox macOS SDK from source. It is inte
 
 ## Requirements
 
-The Mapbox macOS SDK and the macosapp demo application run on macOS 10.10.0 and above.
+The Mapbox macOS SDK and the macosapp demo application run on macOS 10.10.0 or above.
+
+The Mapbox macOS SDK requires Xcode 7.3 or above.
 
 ## Building the SDK
 
@@ -34,6 +36,7 @@ To add an Objective-C class, protocol, category, typedef, enumeration, or global
 To add an Objective-C header or implementation file to the macOS SDK:
 
 1. Add the file to the “dynamic” target’s Headers or Compile Sources build phase, as appropriate. You can either use the Build Phases tab of the project editor or the Target Membership section of the File inspector.
+1. Audit new headers for nullability. Typically, you will wrap a header with `NS_ASSUME_NONNULL_BEGIN` and `NS_ASSUME_NONNULL_END`.
 1. _(Optional.)_ If it’s a public header, change its visibility from Project to Public and import it in [the macOS SDK’s umbrella header](./src/Mapbox.h).
 1. _(Optional.)_ If the file would also be used by the iOS SDK, make sure it’s in [platform/darwin/src/](../darwin/src/), then consult [the companion iOS document](../ios/DEVELOPING.md#adding-a-source-code-file) for further instructions.
 
diff --git a/platform/macos/INSTALL.md b/platform/macos/INSTALL.md
index 07aae88a2e..665af128c5 100644
--- a/platform/macos/INSTALL.md
+++ b/platform/macos/INSTALL.md
@@ -4,7 +4,7 @@ This document explains how to build the Mapbox macOS SDK and integrate it into y
 
 ### Requirements
 
-The Mapbox macOS SDK requires the macOS 10.10.0 SDK or above.
+The Mapbox macOS SDK requires the macOS 10.10.0 SDK (or above) and Xcode 7.3 (or above).
 
 ### Building the SDK
 
diff --git a/platform/macos/src/MGLAnnotationImage.h b/platform/macos/src/MGLAnnotationImage.h
index ad44993ee1..37d43d7277 100644
--- a/platform/macos/src/MGLAnnotationImage.h
+++ b/platform/macos/src/MGLAnnotationImage.h
@@ -1,7 +1,5 @@
 #import <AppKit/AppKit.h>
 
-#import "MGLTypes.h"
-
 NS_ASSUME_NONNULL_BEGIN
 
 /**
diff --git a/platform/macos/src/MGLMapView.h b/platform/macos/src/MGLMapView.h
index 9d44632196..fb2572ec08 100644
--- a/platform/macos/src/MGLMapView.h
+++ b/platform/macos/src/MGLMapView.h
@@ -1,6 +1,7 @@
 #import <Cocoa/Cocoa.h>
 #import <CoreLocation/CoreLocation.h>
 
+#import "MGLTypes.h"
 #import "MGLGeometry.h"
 
 NS_ASSUME_NONNULL_BEGIN
diff --git a/platform/macos/src/MGLMapViewDelegate.h b/platform/macos/src/MGLMapViewDelegate.h
index 6ea69f845a..c84ad42cf3 100644
--- a/platform/macos/src/MGLMapViewDelegate.h
+++ b/platform/macos/src/MGLMapViewDelegate.h
@@ -1,7 +1,5 @@
 #import <Foundation/Foundation.h>
 
-#import "MGLTypes.h"
-
 NS_ASSUME_NONNULL_BEGIN
 
 @class MGLMapView;
diff --git a/platform/macos/src/MGLOpenGLLayer.h b/platform/macos/src/MGLOpenGLLayer.h
index 5c8ac43e9e..832664f397 100644
--- a/platform/macos/src/MGLOpenGLLayer.h
+++ b/platform/macos/src/MGLOpenGLLayer.h
@@ -1,7 +1,5 @@
 #import <Cocoa/Cocoa.h>
 
-#import "MGLTypes.h"
-
 NS_ASSUME_NONNULL_BEGIN
 
 /// A subclass of NSOpenGLLayer that creates the environment mbgl needs to