Remove Borrowed<T>/BorrowedMut<T>, use Option<&T> instead.

components/style/binding_tools/regen.py

@@ -440,7 +440,7 @@ def build(objdir, target_name, debug, debugger, kind_name=None,
             flags.append("{}BorrowedOrNull".format(ty))
             flags.append("--raw-line")
             flags.append("pub type {0}BorrowedOrNull<'a> = \
-::gecko_bindings::sugar::ownership::Borrowed<'a, {0}>;".format(ty))
+Option<&'a {0}>;".format(ty))
             flags.append("--blacklist-type")
             flags.append("{}Borrowed".format(ty))
             flags.append("--raw-line")
@@ -457,7 +457,7 @@ def build(objdir, target_name, debug, debugger, kind_name=None,
             flags.append("{}BorrowedOrNull".format(ty))
             flags.append("--raw-line")
             flags.append("pub type {0}BorrowedOrNull<'a> = \
-::gecko_bindings::sugar::ownership::Borrowed<'a, {0}>;".format(ty))
+Option<&'a {0}>;".format(ty))
             # Right now the only immutable borrow types are ones which we import
             # from the |structs| module. As such, we don't need to create an opaque
             # type with zero_size_type. If we ever introduce immutable borrow types
@@ -487,12 +487,12 @@ def build(objdir, target_name, debug, debugger, kind_name=None,
             flags.append("--blacklist-type")
             flags.append("{}BorrowedOrNull".format(ty))
             flags.append("--raw-line")
-            flags.append("pub type {0}BorrowedOrNull<'a> = ::gecko_bindings::sugar::ownership::Borrowed<'a, {0}>;"
+            flags.append("pub type {0}BorrowedOrNull<'a> = Option<&'a {0}>;"
                          .format(ty))
             flags.append("--blacklist-type")
             flags.append("{}BorrowedMutOrNull".format(ty))
             flags.append("--raw-line")
-            flags.append("pub type {0}BorrowedMutOrNull<'a> = ::gecko_bindings::sugar::ownership::BorrowedMut<'a, {0}>;"
+            flags.append("pub type {0}BorrowedMutOrNull<'a> = Option<&'a mut {0}>;"
                          .format(ty))
             flags.append("--blacklist-type")
             flags.append("{}OwnedOrNull".format(ty))

components/style/gecko/wrapper.rs

@@ -155,7 +155,7 @@ impl TRestyleDamage for GeckoRestyleDamage {
     fn compute(source: &nsStyleContext,
                new_style: &Arc<ComputedValues>) -> Self {
         let context = source as *const nsStyleContext as *mut nsStyleContext;
-        let hint = unsafe { Gecko_CalcStyleDifference(context, new_style.as_borrowed()) };
+        let hint = unsafe { Gecko_CalcStyleDifference(context, new_style.as_borrowed_opt().unwrap()) };
         GeckoRestyleDamage(hint)
     }
 
@@ -329,7 +329,7 @@ impl<'ln> TNode for GeckoNode<'ln> {
     }
 
     fn last_child(&self) -> Option<GeckoNode<'ln>> {
-        unsafe { Gecko_GetLastChild(self.0).borrow_opt().map(GeckoNode) }
+        unsafe { Gecko_GetLastChild(self.0).map(GeckoNode) }
     }
 
     fn prev_sibling(&self) -> Option<GeckoNode<'ln>> {
@@ -397,7 +397,7 @@ impl<'a> Iterator for GeckoChildrenIterator<'a> {
                 curr
             },
             GeckoChildrenIterator::GeckoIterator(ref it) => unsafe {
-                Gecko_GetNextStyleChild(&it).borrow_opt().map(GeckoNode)
+                Gecko_GetNextStyleChild(&it).map(GeckoNode)
             }
         }
     }
@@ -416,7 +416,7 @@ impl<'ld> TDocument for GeckoDocument<'ld> {
 
     fn root_node(&self) -> Option<GeckoNode<'ld>> {
         unsafe {
-            Gecko_GetDocumentElement(self.0).borrow_opt().map(|el| GeckoElement(el).as_node())
+            Gecko_GetDocumentElement(self.0).map(|el| GeckoElement(el).as_node())
         }
     }
 
@@ -470,10 +470,10 @@ impl<'le> TElement for GeckoElement<'le> {
 
     fn style_attribute(&self) -> Option<&Arc<PropertyDeclarationBlock>> {
         let declarations = unsafe { Gecko_GetServoDeclarationBlock(self.0) };
-        if declarations.is_null() {
+        if declarations.is_none() {
             None
         } else {
-            let declarations = declarations.as_arc::<GeckoDeclarationBlock>();
+            let declarations = GeckoDeclarationBlock::arc_from_borrowed(&declarations).unwrap();
             declarations.declarations.as_ref().map(|r| r as *const Arc<_>).map(|ptr| unsafe { &*ptr })
         }
     }

components/style/gecko_bindings/bindings.rs

@@ -2,39 +2,39 @@
 
 use heapsize::HeapSizeOf;
 pub type ServoComputedValuesStrong = ::gecko_bindings::sugar::ownership::Strong<ServoComputedValues>;
-pub type ServoComputedValuesBorrowedOrNull<'a> = ::gecko_bindings::sugar::ownership::Borrowed<'a, ServoComputedValues>;
+pub type ServoComputedValuesBorrowedOrNull<'a> = Option<&'a ServoComputedValues>;
 pub type ServoComputedValuesBorrowed<'a> = &'a ServoComputedValues;
 enum ServoComputedValuesVoid{ }
 pub struct ServoComputedValues(ServoComputedValuesVoid);
 pub type RawServoStyleSheetStrong = ::gecko_bindings::sugar::ownership::Strong<RawServoStyleSheet>;
-pub type RawServoStyleSheetBorrowedOrNull<'a> = ::gecko_bindings::sugar::ownership::Borrowed<'a, RawServoStyleSheet>;
+pub type RawServoStyleSheetBorrowedOrNull<'a> = Option<&'a RawServoStyleSheet>;
 pub type RawServoStyleSheetBorrowed<'a> = &'a RawServoStyleSheet;
 enum RawServoStyleSheetVoid{ }
 pub struct RawServoStyleSheet(RawServoStyleSheetVoid);
 pub type ServoDeclarationBlockStrong = ::gecko_bindings::sugar::ownership::Strong<ServoDeclarationBlock>;
-pub type ServoDeclarationBlockBorrowedOrNull<'a> = ::gecko_bindings::sugar::ownership::Borrowed<'a, ServoDeclarationBlock>;
+pub type ServoDeclarationBlockBorrowedOrNull<'a> = Option<&'a ServoDeclarationBlock>;
 pub type ServoDeclarationBlockBorrowed<'a> = &'a ServoDeclarationBlock;
 enum ServoDeclarationBlockVoid{ }
 pub struct ServoDeclarationBlock(ServoDeclarationBlockVoid);
 pub type RawGeckoNodeBorrowed<'a> = &'a RawGeckoNode;
-pub type RawGeckoNodeBorrowedOrNull<'a> = ::gecko_bindings::sugar::ownership::Borrowed<'a, RawGeckoNode>;
+pub type RawGeckoNodeBorrowedOrNull<'a> = Option<&'a RawGeckoNode>;
 pub type RawGeckoElementBorrowed<'a> = &'a RawGeckoElement;
-pub type RawGeckoElementBorrowedOrNull<'a> = ::gecko_bindings::sugar::ownership::Borrowed<'a, RawGeckoElement>;
+pub type RawGeckoElementBorrowedOrNull<'a> = Option<&'a RawGeckoElement>;
 pub type RawGeckoDocumentBorrowed<'a> = &'a RawGeckoDocument;
-pub type RawGeckoDocumentBorrowedOrNull<'a> = ::gecko_bindings::sugar::ownership::Borrowed<'a, RawGeckoDocument>;
+pub type RawGeckoDocumentBorrowedOrNull<'a> = Option<&'a RawGeckoDocument>;
 pub type RawServoStyleSetBorrowed<'a> = &'a RawServoStyleSet;
 pub type RawServoStyleSetBorrowedMut<'a> = &'a mut RawServoStyleSet;
 pub type RawServoStyleSetOwned = ::gecko_bindings::sugar::ownership::Owned<RawServoStyleSet>;
-pub type RawServoStyleSetBorrowedOrNull<'a> = ::gecko_bindings::sugar::ownership::Borrowed<'a, RawServoStyleSet>;
-pub type RawServoStyleSetBorrowedMutOrNull<'a> = ::gecko_bindings::sugar::ownership::BorrowedMut<'a, RawServoStyleSet>;
+pub type RawServoStyleSetBorrowedOrNull<'a> = Option<&'a RawServoStyleSet>;
+pub type RawServoStyleSetBorrowedMutOrNull<'a> = Option<&'a mut RawServoStyleSet>;
 pub type RawServoStyleSetOwnedOrNull = ::gecko_bindings::sugar::ownership::OwnedOrNull<RawServoStyleSet>;
 enum RawServoStyleSetVoid{ }
 pub struct RawServoStyleSet(RawServoStyleSetVoid);
 pub type StyleChildrenIteratorBorrowed<'a> = &'a StyleChildrenIterator;
 pub type StyleChildrenIteratorBorrowedMut<'a> = &'a mut StyleChildrenIterator;
 pub type StyleChildrenIteratorOwned = ::gecko_bindings::sugar::ownership::Owned<StyleChildrenIterator>;
-pub type StyleChildrenIteratorBorrowedOrNull<'a> = ::gecko_bindings::sugar::ownership::Borrowed<'a, StyleChildrenIterator>;
-pub type StyleChildrenIteratorBorrowedMutOrNull<'a> = ::gecko_bindings::sugar::ownership::BorrowedMut<'a, StyleChildrenIterator>;
+pub type StyleChildrenIteratorBorrowedOrNull<'a> = Option<&'a StyleChildrenIterator>;
+pub type StyleChildrenIteratorBorrowedMutOrNull<'a> = Option<&'a mut StyleChildrenIterator>;
 pub type StyleChildrenIteratorOwnedOrNull = ::gecko_bindings::sugar::ownership::OwnedOrNull<StyleChildrenIterator>;
 enum StyleChildrenIteratorVoid{ }
 pub struct StyleChildrenIterator(StyleChildrenIteratorVoid);

components/style/gecko_bindings/sugar/ownership.rs

@@ -72,16 +72,16 @@ pub unsafe trait HasArcFFI : HasFFI {
     // these methods can't be on Borrowed because it leads to an unspecified
     // impl parameter
     /// Artificially increments the refcount of a (possibly null) borrowed Arc over FFI.
-    unsafe fn addref_opt(ptr: Borrowed<Self::FFIType>) {
-        forget(ptr.as_arc_opt::<Self>().clone())
+    unsafe fn addref_opt(ptr: Option<&Self::FFIType>) {
+        forget(Self::arc_from_borrowed(&ptr).clone())
     }
 
     /// Given a (possibly null) borrowed FFI reference, decrements the refcount.
     /// Unsafe since it doesn't consume the backing Arc. Run it only when you
     /// know that a strong reference to the backing Arc is disappearing
     /// (usually on the C++ side) without running the Arc destructor.
-    unsafe fn release_opt(ptr: Borrowed<Self::FFIType>) {
-        if let Some(arc) = ptr.as_arc_opt::<Self>() {
+    unsafe fn release_opt(ptr: Option<&Self::FFIType>) {
+        if let Some(arc) = Self::arc_from_borrowed(&ptr) {
             let _: Arc<_> = ptr::read(arc as *const Arc<_>);
         }
     }
@@ -108,140 +108,17 @@ pub unsafe trait HasArcFFI : HasFFI {
             transmute::<&&Self::FFIType, &Arc<Self>>(ptr)
         }
     }
-}
-
-#[repr(C)]
-/// Gecko-FFI-safe borrowed type
-/// This can be null.
-pub struct Borrowed<'a, T: 'a> {
-    ptr: *const T,
-    _marker: PhantomData<&'a T>,
-}
-
-#[repr(C)]
-/// Gecko-FFI-safe mutably borrowed type
-/// This can be null.
-pub struct BorrowedMut<'a, T: 'a> {
-    ptr: *mut T,
-    _marker: PhantomData<&'a mut T>,
-}
-
-// manual impls because derive doesn't realize that `T: Clone` isn't necessary
-impl<'a, T> Copy for Borrowed<'a, T> {}
-
-impl<'a, T> Clone for Borrowed<'a, T> {
-    #[inline]
-    fn clone(&self) -> Self { *self }
-}
-
-impl<'a, T> Borrowed<'a, T> {
-    #[inline]
-    pub fn is_null(self) -> bool {
-        self.ptr == ptr::null()
-    }
 
     #[inline]
-    /// Like Deref, but gives an Option
-    pub fn borrow_opt(self) -> Option<&'a T> {
-        if self.is_null() {
-            None
-        } else {
-            Some(unsafe { &*self.ptr })
-        }
-    }
-
-    #[inline]
-    /// Borrowed<GeckoType> -> Option<&Arc<ServoType>>
-    pub fn as_arc_opt<U>(&self) -> Option<&Arc<U>> where U: HasArcFFI<FFIType = T> {
+    fn arc_from_borrowed<'a>(ptr: &'a Option<&Self::FFIType>) -> Option<&'a Arc<Self>> {
         unsafe {
-            if self.is_null() {
-                None
+            if let Some(ref reference) = *ptr {
+                Some(transmute::<&&Self::FFIType, &Arc<_>>(reference))
             } else {
-                Some(transmute::<&Borrowed<_>, &Arc<_>>(self))
+                None
             }
         }
     }
-
-    #[inline]
-    /// Converts a borrowed FFI reference to a borrowed Arc.
-    /// Panics on null.
-    ///
-    /// &Borrowed<GeckoType> -> &Arc<ServoType>
-    pub fn as_arc<U>(&self) -> &Arc<U> where U: HasArcFFI<FFIType = T> {
-        self.as_arc_opt().unwrap()
-    }
-
-    #[inline]
-    /// Borrowed<ServoType> -> Borrowed<GeckoType>
-    pub fn as_ffi(self) -> Borrowed<'a, <Self as HasFFI>::FFIType> where Self: HasSimpleFFI {
-        unsafe { transmute(self) }
-    }
-
-    #[inline]
-    /// Borrowed<GeckoType> -> Borrowed<ServoType>
-    pub fn from_ffi<U>(self) -> Borrowed<'a, U> where U: HasSimpleFFI<FFIType = T> {
-        unsafe { transmute(self) }
-    }
-
-    #[inline]
-    /// Borrowed<GeckoType> -> &ServoType
-    pub fn as_servo_ref<U>(self) -> Option<&'a U> where U: HasSimpleFFI<FFIType = T> {
-        self.borrow_opt().map(HasSimpleFFI::from_ffi)
-    }
-
-    pub fn null() -> Borrowed<'static, T> {
-        Borrowed {
-            ptr: ptr::null_mut(),
-            _marker: PhantomData
-        }
-    }
-}
-
-impl<'a, T> BorrowedMut<'a, T> {
-    #[inline]
-    /// Like DerefMut, but gives an Option
-    pub fn borrow_mut_opt(self) -> Option<&'a mut T> {
-        // We have two choices for the signature here, it can either be
-        // Self -> Option<&'a mut T> or
-        // &'b mut Self -> Option<'b mut T>
-        // The former consumes the BorrowedMut (which isn't Copy),
-        // which can be annoying. The latter only temporarily
-        // borrows it, so the return value can't exit the scope
-        // even if Self has a longer lifetime ('a)
-        //
-        // This is basically the implicit "reborrow" pattern used with &mut
-        // not cleanly translating to our custom types.
-
-        // I've chosen the former solution -- you can manually convert back
-        // if you need to reuse the BorrowedMut.
-        if self.is_null() {
-            None
-        } else {
-            Some(unsafe { &mut *self.ptr })
-        }
-    }
-
-    #[inline]
-    /// BorrowedMut<GeckoType> -> &mut ServoType
-    pub fn as_servo_mut_ref<U>(self) -> Option<&'a mut U> where U: HasSimpleFFI<FFIType = T> {
-        self.borrow_mut_opt().map(HasSimpleFFI::from_ffi_mut)
-    }
-
-    pub fn null_mut() -> BorrowedMut<'static, T> {
-        BorrowedMut {
-            ptr: ptr::null_mut(),
-            _marker: PhantomData
-        }
-    }
-}
-
-// technically not how we're supposed to use
-// Deref, but that's a minor style issue
-impl<'a, T> Deref for BorrowedMut<'a, T> {
-    type Target = Borrowed<'a, T>;
-    fn deref(&self) -> &Self::Target {
-        unsafe { transmute(self) }
-    }
 }
 
 #[repr(C)]
@@ -299,12 +176,8 @@ pub unsafe trait FFIArcHelpers {
     fn into_strong(self) -> Strong<<Self::Inner as HasFFI>::FFIType>;
     /// Produces a (nullable) borrowed FFI reference by borrowing an Arc.
     ///
-    /// &Arc<ServoType> -> Borrowed<GeckoType>
-    fn as_borrowed_opt(&self) -> Borrowed<<Self::Inner as HasFFI>::FFIType>;
-    /// Produces a borrowed FFI reference by borrowing an Arc.
-    ///
-    /// &Arc<ServoType> -> &GeckoType
-    fn as_borrowed(&self) -> &<Self::Inner as HasFFI>::FFIType;
+    /// &Arc<ServoType> -> Option<&GeckoType>
+    fn as_borrowed_opt(&self) -> Option<&<Self::Inner as HasFFI>::FFIType>;
 }
 
 unsafe impl<T: HasArcFFI> FFIArcHelpers for Arc<T> {
@@ -314,13 +187,8 @@ unsafe impl<T: HasArcFFI> FFIArcHelpers for Arc<T> {
         unsafe { transmute(self) }
     }
     #[inline]
-    fn as_borrowed_opt(&self) -> Borrowed<T::FFIType> {
-        let borrowedptr = self as *const Arc<T> as *const Borrowed<T::FFIType>;
-        unsafe { ptr::read(borrowedptr) }
-    }
-    #[inline]
-    fn as_borrowed(&self) -> &T::FFIType {
-        let borrowedptr = self as *const Arc<T> as *const & T::FFIType;
+    fn as_borrowed_opt(&self) -> Option<&T::FFIType> {
+        let borrowedptr = self as *const Arc<T> as *const Option<&T::FFIType>;
         unsafe { ptr::read(borrowedptr) }
     }
 }
@@ -387,11 +255,11 @@ impl<T> OwnedOrNull<T> {
         }
     }
 
-    pub fn borrow(&self) -> Borrowed<T> {
+    pub fn borrow(&self) -> Option<&T> {
         unsafe { transmute(self) }
     }
 
-    pub fn borrow_mut(&self) -> BorrowedMut<T> {
+    pub fn borrow_mut(&self) -> Option<&mut T> {
         unsafe { transmute(self) }
     }
 }

components/style/properties/gecko.mako.rs

@@ -27,6 +27,7 @@ use gecko_bindings::bindings::{Gecko_FontFamilyList_Clear, Gecko_InitializeImage
 use gecko_bindings::bindings::ServoComputedValuesBorrowedOrNull;
 use gecko_bindings::structs;
 use gecko_bindings::sugar::ns_style_coord::{CoordDataValue, CoordData, CoordDataMut};
+use gecko_bindings::sugar::ownership::HasArcFFI;
 use gecko::values::{StyleCoordHelpers, GeckoStyleCoordConvertible, convert_nscolor_to_rgba};
 use gecko::values::convert_rgba_to_nscolor;
 use gecko::values::round_border_to_device_pixels;
@@ -1916,7 +1917,7 @@ clip-path
 #[allow(non_snake_case, unused_variables)]
 pub extern "C" fn Servo_GetStyle${style_struct.gecko_name}(computed_values:
         ServoComputedValuesBorrowedOrNull) -> *const ${style_struct.gecko_ffi_name} {
-    computed_values.as_arc::<ComputedValues>().get_${style_struct.name_lower}().get_gecko()
+    ComputedValues::arc_from_borrowed(&computed_values).unwrap().get_${style_struct.name_lower}().get_gecko()
         as *const ${style_struct.gecko_ffi_name}
 }
 </%def>

ports/geckolib/glue.rs

@@ -252,7 +252,7 @@ pub extern "C" fn Servo_ComputedValues_GetForAnonymousBox(parent_style_or_null:
     let pseudo = PseudoElement::from_atom_unchecked(atom, /* anon_box = */ true);
 
 
-    let maybe_parent = parent_style_or_null.as_arc_opt();
+    let maybe_parent = ComputedValues::arc_from_borrowed(&parent_style_or_null);
     let new_computed = data.stylist.precomputed_values_for_pseudo(&pseudo, maybe_parent);
     new_computed.map_or(Strong::null(), |c| c.into_strong())
 }
@@ -309,10 +309,11 @@ pub extern "C" fn Servo_ComputedValues_GetForPseudoElement(parent_style: ServoCo
 #[no_mangle]
 pub extern "C" fn Servo_ComputedValues_Inherit(parent_style: ServoComputedValuesBorrowedOrNull)
      -> ServoComputedValuesStrong {
-    let style = if parent_style.is_null() {
-        Arc::new(ComputedValues::initial_values().clone())
+    let maybe_arc = ComputedValues::arc_from_borrowed(&parent_style);
+    let style = if let Some(reference) = maybe_arc.as_ref() {
+        ComputedValues::inherit_from(reference)
     } else {
-        ComputedValues::inherit_from(parent_style.as_arc())
+        Arc::new(ComputedValues::initial_values().clone())
     };
     style.into_strong()
 }