Add host_state() accessors to InstanceContents and VMContext too.

lib/runtime/src/instance.rs

@@ -409,6 +409,11 @@ impl InstanceContents {
 
         foreign_instance_contents.memory_size(foreign_index)
     }
+
+    /// Return a reference to the custom state attached to this instance.
+    pub fn host_state(&mut self) -> &mut Any {
+        return &mut *self.host_state;
+    }
 }
 
 /// A wrapper around an `Mmap` holding an `InstanceContents`.
@@ -686,7 +691,7 @@ impl Instance {
 
     /// Return a reference to the custom state attached to this instance.
     pub fn host_state(&mut self) -> &mut Any {
-        return &mut *self.mmap_field.contents_mut().host_state;
+        return self.mmap_field.contents_mut().host_state();
     }
 }
 

lib/runtime/src/vmcontext.rs

@@ -2,6 +2,7 @@
 //! fields that compiled wasm code accesses directly.
 
 use crate::instance::InstanceContents;
+use core::any::Any;
 use core::{ptr, u32};
 
 /// An imported function.
@@ -478,9 +479,20 @@ pub struct VMContext {}
 
 impl VMContext {
     /// Return a mutable reference to the associated `Instance`.
+    ///
+    /// This is unsafe because it doesn't work on just any `VMContext`, it must
+    /// be a `VMContext` allocated as part of an `Instance`.
     #[allow(clippy::cast_ptr_alignment)]
     pub(crate) unsafe fn instance_contents(&mut self) -> &mut InstanceContents {
         &mut *((self as *mut Self as *mut u8).offset(-InstanceContents::vmctx_offset())
             as *mut InstanceContents)
     }
+
+    /// Return a mutable reference to the host state associated with `Instance`.
+    ///
+    /// This is unsafe because it doesn't work on just any `VMContext`, it must
+    /// be a `VMContext` allocated as part of an `Instance`.
+    pub unsafe fn host_state(&mut self) -> &mut Any {
+        self.instance_contents().host_state()
+    }
 }