From 45c9aa7487cf2617126e4c667dbfb0ad3b244b4d Mon Sep 17 00:00:00 2001
From: Anthony Ramine <n.oxyde@gmail.com>
Date: Fri, 13 May 2016 14:23:09 +0200
Subject: [PATCH] Generalise RootedReference

It now becomes RootedReference<'root> and includes an associated type for
the return type of its 'r' method.

This removes the need for OptionalRootedReference.
---
 .../dom/bindings/codegen/CodegenRust.py       |  2 -
 components/script/dom/bindings/js.rs          | 71 ++++++++-----------
 components/script/dom/bindings/trace.rs       |  8 +--
 3 files changed, 32 insertions(+), 49 deletions(-)

diff --git a/components/script/dom/bindings/codegen/CodegenRust.py b/components/script/dom/bindings/codegen/CodegenRust.py
index e66ff0ab8589..7fc824c27b8c 100644
--- a/components/script/dom/bindings/codegen/CodegenRust.py
+++ b/components/script/dom/bindings/codegen/CodegenRust.py
@@ -5505,9 +5505,7 @@ def generate_imports(config, cgthings, descriptors, callbacks=None, dictionaries
         'dom::bindings::iterable::Iterable',
         'dom::bindings::iterable::IteratorType',
         'dom::bindings::js::JS',
-        'dom::bindings::js::OptionalRootedReference',
         'dom::bindings::js::Root',
-        'dom::bindings::js::RootedRcReference',
         'dom::bindings::js::RootedReference',
         'dom::bindings::namespace::NamespaceObjectClass',
         'dom::bindings::namespace::create_namespace_object',
diff --git a/components/script/dom/bindings/js.rs b/components/script/dom/bindings/js.rs
index 24e926bac3a7..6441bed67464 100644
--- a/components/script/dom/bindings/js.rs
+++ b/components/script/dom/bindings/js.rs
@@ -87,6 +87,13 @@ impl<T: Reflectable> JS<T> {
     }
 }
 
+impl<'root, T: Reflectable + 'root> RootedReference<'root> for JS<T> {
+    type Ref = &'root T;
+    fn r(&'root self) -> &'root T {
+        &self
+    }
+}
+
 impl<T: Reflectable> Deref for JS<T> {
     type Target = T;
 
@@ -446,54 +453,25 @@ impl<T: Reflectable> LayoutJS<T> {
     }
 }
 
-/// Get an `&T` out of a `Rc<T>`
-pub trait RootedRcReference<T> {
-    /// Obtain a safe reference to the wrapped non-JS owned value.
-    fn r(&self) -> &T;
-}
-
-impl<T: Reflectable> RootedRcReference<T> for Rc<T> {
-    fn r(&self) -> &T {
-        &*self
-    }
-}
-
-/// Get an `Option<&T>` out of an `Option<Root<T>>`
-pub trait RootedReference<T> {
-    /// Obtain a safe optional reference to the wrapped JS owned-value that
-    /// cannot outlive the lifetime of this root.
-    fn r(&self) -> Option<&T>;
+/// Get a reference out of a rooted value.
+pub trait RootedReference<'root> {
+    /// The type of the reference.
+    type Ref: 'root;
+    /// Obtain a reference out of the rooted value.
+    fn r(&'root self) -> Self::Ref;
 }
 
-impl<T: Reflectable> RootedReference<T> for Option<Rc<T>> {
-    fn r(&self) -> Option<&T> {
-        self.as_ref().map(|root| &**root)
+impl<'root, T: Reflectable + 'root> RootedReference<'root> for Rc<T> {
+    type Ref = &'root T;
+    fn r(&'root self) -> &'root T {
+        self
     }
 }
 
-impl<T: Reflectable> RootedReference<T> for Option<Root<T>> {
-    fn r(&self) -> Option<&T> {
-        self.as_ref().map(|root| &**root)
-    }
-}
-
-/// Get an `Option<&T> out of an `Option<JS<T>>`
-impl<T: Reflectable> RootedReference<T> for Option<JS<T>> {
-    fn r(&self) -> Option<&T> {
-        self.as_ref().map(|inner| &**inner)
-    }
-}
-
-/// Get an `Option<Option<&T>>` out of an `Option<Option<Root<T>>>`
-pub trait OptionalRootedReference<T> {
-    /// Obtain a safe optional optional reference to the wrapped JS owned-value
-    /// that cannot outlive the lifetime of this root.
-    fn r(&self) -> Option<Option<&T>>;
-}
-
-impl<T: Reflectable> OptionalRootedReference<T> for Option<Option<Root<T>>> {
-    fn r(&self) -> Option<Option<&T>> {
-        self.as_ref().map(|inner| inner.r())
+impl<'root, T: RootedReference<'root> + 'root> RootedReference<'root> for Option<T> {
+    type Ref = Option<T::Ref>;
+    fn r(&'root self) -> Option<T::Ref> {
+        self.as_ref().map(RootedReference::r)
     }
 }
 
@@ -617,6 +595,13 @@ impl<T: Reflectable> Root<T> {
     }
 }
 
+impl<'root, T: Reflectable + 'root> RootedReference<'root> for Root<T> {
+    type Ref = &'root T;
+    fn r(&'root self) -> &'root T {
+        self
+    }
+}
+
 impl<T: Reflectable> Deref for Root<T> {
     type Target = T;
     fn deref(&self) -> &T {
diff --git a/components/script/dom/bindings/trace.rs b/components/script/dom/bindings/trace.rs
index 6331a1c3bf3d..4e37dd45aa0a 100644
--- a/components/script/dom/bindings/trace.rs
+++ b/components/script/dom/bindings/trace.rs
@@ -36,7 +36,7 @@ use devtools_traits::CSSError;
 use devtools_traits::WorkerId;
 use dom::abstractworker::SharedRt;
 use dom::bindings::cell::DOMRefCell;
-use dom::bindings::js::{JS, Root};
+use dom::bindings::js::{JS, Root, RootedReference};
 use dom::bindings::refcounted::{Trusted, TrustedPromise};
 use dom::bindings::reflector::{Reflectable, Reflector};
 use dom::bindings::str::{DOMString, USVString};
@@ -553,9 +553,9 @@ impl<'a, T: JSTraceable + Reflectable> RootedVec<'a, JS<T>> {
     }
 }
 
-impl<'a, T: JSTraceable + Reflectable> RootedVec<'a, JS<T>> {
-    /// Obtain a safe slice of references that can't outlive that RootedVec.
-    pub fn r(&self) -> &[&T] {
+impl<'a, 'root, T: JSTraceable + Reflectable + 'root> RootedReference<'root> for RootedVec<'a, JS<T>> {
+    type Ref = &'root [&'root T];
+    fn r(&'root self) -> &'root [&'root T] {
         unsafe { mem::transmute(&self[..]) }
     }
 }