fix: allow dynamic owned resources to be used as borrowed parameters (#7783)

* fix: allow dynamic owned resources to be used as borrowed parameters

Signed-off-by: Roman Volosatovs <rvolosatovs@riseup.net>

* tests: add `can_use_own_for_borrow` test

Signed-off-by: Roman Volosatovs <rvolosatovs@riseup.net>

---------

Signed-off-by: Roman Volosatovs <rvolosatovs@riseup.net>

crates/wasmtime/src/component/func.rs

@@ -362,7 +362,8 @@ impl Func {
         }
 
         for (param, ty) in params.iter().zip(param_tys.iter()) {
-            ty.check(param).context("type mismatch with parameters")?;
+            ty.is_supertype_of(param)
+                .context("type mismatch with parameters")?;
         }
 
         self.call_raw(

crates/wasmtime/src/component/func/host.rs

@@ -385,7 +385,7 @@ where
     let mut cx = LowerContext::new(store, &options, types, instance);
     let instance = cx.instance_type();
     for (val, ty) in result_vals.iter().zip(result_tys.types.iter()) {
-        Type::from(ty, &instance).check(val)?;
+        Type::from(ty, &instance).is_supertype_of(val)?;
     }
     if let Some(cnt) = result_tys.abi.flat_count(MAX_FLAT_RESULTS) {
         let mut dst = storage[..cnt].iter_mut();

crates/wasmtime/src/component/types.rs

@@ -675,9 +675,16 @@ impl Type {
         }
     }
 
-    pub(crate) fn check(&self, value: &Val) -> Result<()> {
+    /// Checks whether type of `value` is a subtype of `self`.
+    ///
+    /// # Errors
+    ///
+    /// Returns an error in case of a type mismatch
+    pub(crate) fn is_supertype_of(&self, value: &Val) -> Result<()> {
         let other = &value.ty();
-        if self == other {
+        if self == other
+            || matches!((self, other), (Self::Borrow(s), Self::Own(other)) if s == other)
+        {
             Ok(())
         } else if mem::discriminant(self) != mem::discriminant(other) {
             Err(anyhow!(

crates/wasmtime/src/component/values.rs

@@ -26,7 +26,7 @@ impl List {
         let element_type = ty.ty();
         for (index, value) in values.iter().enumerate() {
             element_type
-                .check(value)
+                .is_supertype_of(value)
                 .with_context(|| format!("type mismatch for element {index} of list"))?;
         }
 
@@ -83,7 +83,7 @@ impl Record {
                     if name == field.name {
                         field
                             .ty
-                            .check(&value)
+                            .is_supertype_of(&value)
                             .with_context(|| format!("type mismatch for field {name} of record"))?;
 
                         values.push(value);
@@ -150,7 +150,7 @@ impl Tuple {
         }
 
         for (index, (value, ty)) in values.iter().zip(ty.types()).enumerate() {
-            ty.check(value)
+            ty.is_supertype_of(value)
                 .with_context(|| format!("type mismatch for field {index} of tuple"))?;
         }
 
@@ -256,7 +256,7 @@ impl Variant {
 fn typecheck_payload(name: &str, case_type: Option<&Type>, value: Option<&Val>) -> Result<()> {
     match (case_type, value) {
         (Some(expected), Some(actual)) => expected
-            .check(&actual)
+            .is_supertype_of(&actual)
             .with_context(|| format!("type mismatch for case {name} of variant")),
         (None, None) => Ok(()),
         (Some(_), None) => bail!("expected a payload for case `{name}`"),
@@ -341,7 +341,9 @@ impl OptionVal {
     pub fn new(ty: &types::OptionType, value: Option<Val>) -> Result<Self> {
         let value = value
             .map(|value| {
-                ty.ty().check(&value).context("type mismatch for option")?;
+                ty.ty()
+                    .is_supertype_of(&value)
+                    .context("type mismatch for option")?;
 
                 Ok::<_, Error>(value)
             })

tests/all/component_model/resources.rs

@@ -856,6 +856,72 @@ fn cannot_use_borrow_for_own() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn can_use_own_for_borrow() -> Result<()> {
+    let engine = super::engine();
+    let c = Component::new(
+        &engine,
+        r#"
+            (component
+                (import "t" (type $t (sub resource)))
+
+                (core func $drop (canon resource.drop $t))
+
+                (core module $m
+                    (import "" "drop" (func $drop (param i32)))
+                    (func (export "f") (param i32)
+                        (call $drop (local.get 0))
+                    )
+                )
+                (core instance $i (instantiate $m
+                    (with "" (instance
+                        (export "drop" (func $drop))
+                    ))
+                ))
+
+                (func (export "f") (param "x" (borrow $t))
+                    (canon lift (core func $i "f")))
+            )
+        "#,
+    )?;
+
+    struct MyType;
+
+    let mut store = Store::new(&engine, ());
+    let mut linker = Linker::new(&engine);
+    let ty_idx = linker
+        .root()
+        .resource("t", ResourceType::host::<MyType>(), |_, _| Ok(()))?;
+    let i_pre = linker.instantiate_pre(&c)?;
+    let i = i_pre.instantiate(&mut store)?;
+
+    let f = i.get_func(&mut store, "f").unwrap();
+    let f_typed = i.get_typed_func::<(&Resource<MyType>,), ()>(&mut store, "f")?;
+
+    let resource = Resource::new_own(100);
+    f_typed.call(&mut store, (&resource,))?;
+    f_typed.post_return(&mut store)?;
+
+    let resource = Resource::new_borrow(200);
+    f_typed.call(&mut store, (&resource,))?;
+    f_typed.post_return(&mut store)?;
+
+    let resource =
+        Resource::<MyType>::new_own(300).try_into_resource_any(&mut store, &i_pre, ty_idx)?;
+    f.call(&mut store, &[Val::Resource(resource)], &mut [])?;
+    f.post_return(&mut store)?;
+    resource.resource_drop(&mut store)?;
+
+    // TODO: Enable once https://github.com/bytecodealliance/wasmtime/issues/7793 is fixed
+    //let resource =
+    //    Resource::<MyType>::new_borrow(400).try_into_resource_any(&mut store, &i_pre, ty_idx)?;
+    //f.call(&mut store, &[Val::Resource(resource)], &mut [])?;
+    //f.post_return(&mut store)?;
+    //resource.resource_drop(&mut store)?;
+
+    Ok(())
+}
+
 #[test]
 fn passthrough_wrong_type() -> Result<()> {
     let engine = super::engine();