Wasmtime: fix PartialEq implementation for RegisteredType (bytecodealliance#10091)

We were incorrectly checking whether they were in the same rec
group (i.e. whether the two `RegisteredType`s had the same `RecGroupEntry`)
rather than whether they were actually the same type or not, even if they were
in the same rec group.

This fixes one of two issues reported in bytecodealliance#9714

Author: fitzgen

crates/wasmtime/src/engine.rs

@@ -70,6 +70,14 @@ struct EngineInner {
     compatible_with_native_host: OnceLock<Result<(), String>>,
 }
 
+impl core::fmt::Debug for Engine {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        f.debug_tuple("Engine")
+            .field(&Arc::as_ptr(&self.inner))
+            .finish()
+    }
+}
+
 impl Default for Engine {
     fn default() -> Engine {
         Engine::new(&Config::default()).unwrap()

crates/wasmtime/src/runtime/type_registry.rs

@@ -263,11 +263,11 @@ impl core::ops::Deref for RegisteredType {
 
 impl PartialEq for RegisteredType {
     fn eq(&self, other: &Self) -> bool {
-        let eq = Arc::ptr_eq(&self.entry.0, &other.entry.0);
+        let eq = self.index == other.index && Engine::same(&self.engine, &other.engine);
 
         if cfg!(debug_assertions) {
             if eq {
-                assert!(Engine::same(&self.engine, &other.engine));
+                assert!(Arc::ptr_eq(&self.entry.0, &other.entry.0));
                 assert_eq!(self.ty, other.ty);
             } else {
                 assert!(self.ty != other.ty || !Engine::same(&self.engine, &other.engine));
@@ -365,6 +365,9 @@ impl RegisteredType {
         ty: Arc<WasmSubType>,
         layout: Option<GcLayout>,
     ) -> Self {
+        log::trace!(
+            "RegisteredType::from_parts({engine:?}, {entry:?}, {index:?}, {ty:?}, {layout:?})"
+        );
         debug_assert!(entry.0.registrations.load(Acquire) != 0);
         RegisteredType {
             engine,

tests/all/arrays.rs

@@ -1,16 +1,6 @@
+use super::gc_store;
 use wasmtime::*;
 
-fn gc_store() -> Result<Store<()>> {
-    let _ = env_logger::try_init();
-
-    let mut config = Config::new();
-    config.wasm_function_references(true);
-    config.wasm_gc(true);
-
-    let engine = Engine::new(&config)?;
-    Ok(Store::new(&engine, ()))
-}
-
 #[test]
 fn array_new_empty() -> Result<()> {
     let mut store = gc_store()?;

tests/all/main.rs

@@ -106,3 +106,14 @@ pub(crate) fn small_pool_config() -> wasmtime::PoolingAllocationConfig {
 
     config
 }
+
+pub(crate) fn gc_store() -> wasmtime::Result<wasmtime::Store<()>> {
+    let _ = env_logger::try_init();
+
+    let mut config = wasmtime::Config::new();
+    config.wasm_function_references(true);
+    config.wasm_gc(true);
+
+    let engine = wasmtime::Engine::new(&config)?;
+    Ok(wasmtime::Store::new(&engine, ()))
+}

tests/all/structs.rs

@@ -1,16 +1,6 @@
+use super::gc_store;
 use wasmtime::*;
 
-fn gc_store() -> Result<Store<()>> {
-    let _ = env_logger::try_init();
-
-    let mut config = Config::new();
-    config.wasm_function_references(true);
-    config.wasm_gc(true);
-
-    let engine = Engine::new(&config)?;
-    Ok(Store::new(&engine, ()))
-}
-
 #[test]
 fn struct_new_empty() -> Result<()> {
     let mut store = gc_store()?;
@@ -737,3 +727,26 @@ fn can_put_funcrefs_in_structs() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+#[cfg_attr(miri, ignore)]
+fn struct_ref_struct_in_same_rec_group_in_global() -> Result<()> {
+    let mut store = gc_store()?;
+    let module = Module::new(
+        store.engine(),
+        r#"
+            (module
+                (rec
+                    (type $b (struct))
+                    (type $a (struct (field (ref $b))))
+                )
+                (global (ref $a)
+                    struct.new_default $b
+                    struct.new $a
+                )
+            )
+        "#,
+    )?;
+    let _instance = Instance::new(&mut store, &module, &[])?;
+    Ok(())
+}