require memory for async lifts as needed

Per WebAssembly/component-model#575, both `wasm-tools`
and Wasmtime have been too permissive, allowing async lifts to optionally omit a
memory canonopt if only the return type (and not the parameter types) would need
one.  This fixes validation to require the option in such cases.

Signed-off-by: Joel Dice <[email protected]>

Author: dicej

crates/wasmparser/src/validator/component_types.rs

@@ -1275,6 +1275,21 @@ impl ComponentFuncType {
                 sig.results.assert_push(ValType::I32);
             }
             (Abi::Lift, Concurrency::Async { callback }) => {
+                if let Some(ty) = &self.result {
+                    // The result of an async lift will be returned via a call
+                    // to `task.return` rather than the lifted function itself.
+                    // Here we require a memory if either the return type
+                    // contains a pointer or has a flattened form that exceeds
+                    // `MAX_FLAT_FUNC_PARAMS`.
+                    //
+                    // Note that the return type itself has no effect on the
+                    // expected core signature of the lifted function.
+
+                    let overflow =
+                        !ty.push_wasm_types(types, &mut LoweredTypes::new(MAX_FLAT_FUNC_PARAMS));
+
+                    options.require_memory_if(offset, || overflow || ty.contains_ptr(types))?;
+                }
                 if callback.is_some() {
                     sig.results.assert_push(ValType::I32);
                 }

tests/cli/component-model/async/lift.wast

@@ -108,3 +108,35 @@
   )
   "cannot specify callback without async"
 )
+
+;; async lift; missing memory (needed for string return value)
+(assert_invalid
+  (component
+    (core module $m
+      (func (export "callback") (param i32 i32 i32) (result i32) unreachable)
+      (func (export "foo") (result i32) unreachable)
+    )
+    (core instance $i (instantiate $m))
+
+    (func (export "foo") (result string)
+      (canon lift (core func $i "foo") async (callback (func $i "callback")))
+    )
+  )
+  "canonical option `memory` is required"
+)
+
+;; async lift; missing memory (needed for return value exceeding MAX_FLAT_PARAMS)
+(assert_invalid
+  (component
+    (core module $m
+      (func (export "callback") (param i32 i32 i32) (result i32) unreachable)
+      (func (export "foo") (result i32) unreachable)
+    )
+    (core instance $i (instantiate $m))
+
+    (func (export "foo") (result (tuple u32 u32 u32 u32 u32 u32 u32 u32 u32 u32 u32 u32 u32 u32 u32 u32 u32))
+      (canon lift (core func $i "foo") async (callback (func $i "callback")))
+    )
+  )
+  "canonical option `memory` is required"
+)

tests/snapshots/cli/component-model/async/lift.wast.json

@@ -48,6 +48,20 @@
       "filename": "lift.6.wasm",
       "module_type": "binary",
       "text": "cannot specify callback without async"
+    },
+    {
+      "type": "assert_invalid",
+      "line": 114,
+      "filename": "lift.7.wasm",
+      "module_type": "binary",
+      "text": "canonical option `memory` is required"
+    },
+    {
+      "type": "assert_invalid",
+      "line": 130,
+      "filename": "lift.8.wasm",
+      "module_type": "binary",
+      "text": "canonical option `memory` is required"
     }
   ]
 }