style: Fix servo build, and appease tidy / fmt.

components/to_shmem/Cargo.toml

@@ -10,13 +10,14 @@ name = "to_shmem"
 path = "lib.rs"
 
 [features]
-servo = ["serde", "cssparser/serde"]
+servo = ["serde", "cssparser/serde", "string_cache"]
 gecko = []
 
 [dependencies]
 cssparser = "0.25"
-serde = {version = "1.0", optional = true}
+serde = { version = "1.0", optional = true }
 servo_arc = { path = "../servo_arc" }
 smallbitvec = "2.1.1"
 smallvec = "0.6.6"
+string_cache = { version = "0.7", optional = true }
 thin-slice = "0.1.0"

components/to_shmem/lib.rs

@@ -16,6 +16,8 @@ extern crate cssparser;
 extern crate servo_arc;
 extern crate smallbitvec;
 extern crate smallvec;
+#[cfg(feature = "string_cache")]
+extern crate string_cache;
 extern crate thin_slice;
 
 use servo_arc::{Arc, ThinArc};
@@ -193,16 +195,18 @@ pub trait ToShmem: Sized {
 
 #[macro_export]
 macro_rules! impl_trivial_to_shmem {
-    ($($ty:ty),*) => {$(
-        impl $crate::ToShmem for $ty {
-            fn to_shmem(
-                &self,
-                _builder: &mut $crate::SharedMemoryBuilder,
-            ) -> ::std::mem::ManuallyDrop<Self> {
-                ::std::mem::ManuallyDrop::new(*self)
+    ($($ty:ty),*) => {
+        $(
+            impl $crate::ToShmem for $ty {
+                fn to_shmem(
+                    &self,
+                    _builder: &mut $crate::SharedMemoryBuilder,
+                ) -> ::std::mem::ManuallyDrop<Self> {
+                    ::std::mem::ManuallyDrop::new(*self)
+                }
             }
-        }
-    )*};
+        )*
+    };
 }
 
 impl_trivial_to_shmem!(
@@ -522,3 +526,17 @@ impl ToShmem for SmallBitVec {
         ManuallyDrop::new(unsafe { SmallBitVec::from_storage(storage) })
     }
 }
+
+#[cfg(feature = "string_cache")]
+impl<Static: string_cache::StaticAtomSet> ToShmem for string_cache::Atom<Static> {
+    fn to_shmem(&self, _: &mut SharedMemoryBuilder) -> ManuallyDrop<Self> {
+        // NOTE(emilio): In practice, this can be implemented trivially if
+        // string_cache could expose the implementation detail of static atoms
+        // being an index into the static table (and panicking in the
+        // non-static, non-inline cases).
+        unimplemented!(
+            "If servo wants to share stylesheets across processes, \
+             then ToShmem for Atom needs to be implemented"
+        )
+    }
+}