Squash warnings on zero-sized structs servo#87.

Changes zero-sized structs to an `enum` and removed unused macro use statement.

src/color_space.rs

@@ -10,8 +10,9 @@
 use core_foundation::base::{CFRelease, CFRetain, CFTypeID, CFTypeRef, TCFType};
 use std::mem;
 
-#[repr(C)]
-pub struct __CGColorSpace;
+// This is an enum due to zero-sized types warnings.
+// For more details see https://github.com/rust-lang/rust/issues/27303
+pub enum __CGColorSpace {}
 
 pub type CGColorSpaceRef = *const __CGColorSpace;
 

src/data_provider.rs

@@ -26,8 +26,9 @@ pub type CGDataProviderReleaseBytePointerCallback = Option<unsafe extern fn (*mu
 pub type CGDataProviderReleaseDataCallback = Option<unsafe extern fn (*mut c_void, *const c_void, size_t)>;
 pub type CGDataProviderGetBytesAtPositionCallback = Option<unsafe extern fn (*mut c_void, *mut c_void, off_t, size_t)>;
 
-#[repr(C)]
-pub struct __CGDataProvider;
+// This is an enum due to zero-sized types warnings.
+// For more details see https://github.com/rust-lang/rust/issues/27303
+pub enum __CGDataProvider {}
 
 pub type CGDataProviderRef = *const __CGDataProvider;
 

src/event.rs

@@ -12,6 +12,7 @@ pub type CGKeyCode = libc::uint16_t;
 ///
 /// [Ref](http://opensource.apple.com/source/IOHIDFamily/IOHIDFamily-700/IOHIDSystem/IOKit/hidsystem/IOLLEvent.h)
 bitflags! {
+    #[repr(C)]
     pub struct CGEventFlags: u64 {
         const CGEventFlagNull = 0;
 
@@ -88,8 +89,9 @@ pub enum CGEventTapLocation {
     AnnotatedSession,
 }
 
-#[repr(C)]
-pub struct __CGEvent;
+// This is an enum due to zero-sized types warnings.
+// For more details see https://github.com/rust-lang/rust/issues/27303
+pub enum __CGEvent {}
 
 pub type CGEventRef = *const __CGEvent;
 

src/event_source.rs

@@ -12,8 +12,9 @@ pub enum CGEventSourceStateID {
     HIDSystemState = 1,
 }
 
-#[repr(C)]
-pub struct __CGEventSource;
+// This is an enum due to zero-sized types warnings.
+// For more details see https://github.com/rust-lang/rust/issues/27303
+pub enum __CGEventSource {}
 
 pub type CGEventSourceRef = *const __CGEventSource;
 

src/image.rs

@@ -27,8 +27,9 @@ pub enum CGImageByteOrderInfo {
     CGImageByteOrder32Big = (4 << 12)
 }
 
-#[repr(C)]
-pub struct __CGImage;
+// This is an enum due to zero-sized types warnings.
+// For more details see https://github.com/rust-lang/rust/issues/27303
+pub enum __CGImage {}
 
 pub type CGImageRef = *const __CGImage;
 

src/lib.rs

@@ -8,7 +8,6 @@
 // except according to those terms.
 
 extern crate libc;
-#[macro_use]
 extern crate core_foundation;
 
 #[macro_use]