Fix a panic with Func::new and reference types

crates/wasmtime/src/runtime.rs

@@ -609,6 +609,12 @@ impl Config {
             .finish(settings::Flags::new(self.flags.clone()))
     }
 
+    pub(crate) fn target_isa_with_reference_types(&self) -> Box<dyn TargetIsa> {
+        let mut flags = self.flags.clone();
+        flags.set("enable_safepoints", "true").unwrap();
+        self.isa_flags.clone().finish(settings::Flags::new(flags))
+    }
+
     pub(crate) fn validator(&self) -> Validator {
         let mut ret = Validator::new();
         ret.wasm_threads(self.wasm_threads)

crates/wasmtime/src/trampoline/func.rs

@@ -206,7 +206,10 @@ pub fn create_handle_with_function(
     func: Box<dyn Fn(*mut VMContext, *mut u128) -> Result<(), Trap>>,
     store: &Store,
 ) -> Result<(StoreInstanceHandle, VMTrampoline)> {
-    let isa = store.engine().config().target_isa();
+    // Note that we specifically enable reference types here in our ISA because
+    // `Func::new` is intended to be infallible, but our signature may use
+    // reference types which requires safepoints.
+    let isa = store.engine().config().target_isa_with_reference_types();
 
     let pointer_type = isa.pointer_type();
     let sig = ft.get_wasmtime_signature(pointer_type);

tests/all/func.rs

@@ -507,3 +507,18 @@ fn pass_cross_store_arg() -> anyhow::Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn externref_signature_no_reference_types() -> anyhow::Result<()> {
+    let store = Store::default();
+    Func::wrap(&store, |_: Option<Func>| {});
+    Func::new(
+        &store,
+        FuncType::new(
+            Box::new([ValType::FuncRef, ValType::ExternRef]),
+            Box::new([ValType::FuncRef, ValType::ExternRef]),
+        ),
+        |_, _, _| Ok(()),
+    );
+    Ok(())
+}