Merge pull request #234 from jacob-hughes/remove_finalizer_safe

Remove FinalizerSafe trait

src/lib/vm/objects/block.rs

@@ -74,14 +74,6 @@ pub struct Block {
     pub method_stack_base: usize,
 }
 
-// The following impls are needed to allow the GC to finalise `Block`. By
-// default, `Block` is not `FinalizerSafe` because it has fields to other `Gc`s.
-// These fields would be unsound to access inside a `drop` method, so this
-// explicit impl is needed to tell the compiler we are not doing that. The only
-// time a `Block` is shared between threads is inside a finaliser, which is
-// Sync-safe because we guarantee it will not be accessed at the same time as
-// the main-thread.
-unsafe impl FinalizerSafe for Block {}
 unsafe impl Sync for Block {}
 
 impl Obj for Block {

src/lib/vm/objects/class.rs

@@ -36,11 +36,6 @@ pub struct Class {
     inst_vars: UnsafeCell<Vec<Val>>,
 }
 
-// This is safe because there is no non-GC'd shared ownership inside `Class`.
-// This means that even though a finalizer will call its drop methods in another
-// thread, it is guaranteed that the finalizer thread will be the only thread
-// accessing its data.
-unsafe impl FinalizerSafe for Class {}
 unsafe impl Sync for Class {}
 
 impl Obj for Class {

src/lib/vm/objects/method.rs

@@ -17,11 +17,6 @@ pub struct Method {
     pub func: Function,
 }
 
-// By default, `Method` is not `FinalizerSafe` because it contains a `Cell`
-// field. Cell is `!Sync` so it would be unsound to access inside a `drop`
-// method. This explicit impl is needed to tell the compiler we are not doing
-// that.
-unsafe impl FinalizerSafe for Method {}
 unsafe impl Sync for Method {}
 
 impl Obj for Method {

src/lib/vm/objects/mod.rs

@@ -80,7 +80,7 @@ impl ObjType {
 /// The main SOM Object trait. Notice that code should almost never call these functions directly:
 /// you should instead call the equivalent function in the `Val` struct.
 #[narrowable_alloy(ThinObj)]
-pub trait Obj: std::fmt::Debug + Send + Sync + FinalizerSafe {
+pub trait Obj: std::fmt::Debug + Send + Sync {
     /// What `ObjType` does this `Val` represent?
     fn dyn_objtype(self: Gc<Self>) -> ObjType;
 

src/lib/vm/objects/string_.rs

@@ -28,11 +28,6 @@ pub struct String_ {
     s: String,
 }
 
-// This is safe because there is no non-GC'd shared ownership inside `String_`.
-// This means that even though a finalizer will call its drop methods in another
-// thread, it is guaranteed that the finalizer thread will be the only thread
-// accessing its data.
-unsafe impl FinalizerSafe for String_ {}
 unsafe impl Sync for String_ {}
 
 impl Obj for String_ {