[JSC] Error.isError(WebAssembly.Exception) should be false

tetsuharuohzeki · sosukesuzuki · commit 6376164b58fe · 2025-12-23T18:24:00.000-08:00
https://bugs.webkit.org/show_bug.cgi?id=304410 Reviewed by Yusuke Suzuki and Sosuke Suzuki. According to the spec discussion, the current `WebAssembly.Exception` does not have `[[ErrorData]]` semantically. So `Error.isError(WebAssembly.Exception)` should be `false`. - WebAssembly/spec#1914 - https://webassembly.github.io/spec/js-api/#exceptions Test: JSTests/wasm/stress/exception-thrown-out-of-wasm-integration-error-is-error.js * JSTests/wasm/stress/exception-thrown-out-of-wasm-integration-error-is-error.js: Added. (import.Builder.from.string_appeared_here.import.as.assert.from.string_appeared_here.catch): * Source/JavaScriptCore/wasm/js/JSWebAssemblyException.cpp: (JSC::JSWebAssemblyException::createStructure): Canonical link: https://commits.webkit.org/304917@main
diff --git a/JSTests/wasm/stress/exception-thrown-out-of-wasm-integration-error-is-error.js b/JSTests/wasm/stress/exception-thrown-out-of-wasm-integration-error-is-error.js
@@ -0,0 +1,39 @@
+import Builder from '../Builder.js'
+import * as assert from '../assert.js'
+
+{
+    const b = new Builder();
+    b.Type().End()
+        .Function().End()
+        .Exception().Signature({ params: [] }).End()
+        .Export().Function("call")
+            .Exception("foo", 0)
+        .End()
+        .Code()
+            .Function("call", { params: [], ret: "i32" })
+            .Throw(0)
+            .I32Const(1)
+            .End()
+        .End()
+
+    const bin = b.WebAssembly().get();
+    const module = new WebAssembly.Module(bin);
+    const instance = new WebAssembly.Instance(module);
+
+    let hasCaught = false;
+    try {
+        instance.exports.call();
+    } catch (e) {
+        hasCaught = true;
+        assert.instanceof(e, WebAssembly.Exception, 'must be an instance of WebAssembly.Exception');
+        // By the current (22 November 2025) spec semantics, `WebAssembly.Exception` does not have `[[ErrorData]]` in ECMA262 concept.
+        // This means `Error.isError(<a instance of WebAssembly.Exception>)` should be `false`.
+        //
+        // - https://webassembly.github.io/spec/js-api/#exceptions
+        // - https://github.com/WebAssembly/spec/issues/1914
+        // - https://tc39.es/ecma262/multipage/fundamental-objects.html#sec-properties-of-error-instances
+        assert.eq(Error.isError(e), false, 'Error.isError(WebAssembly.Exception) should be false');
+    }
+
+    assert.truthy(hasCaught, 'expected assertion was not called');
+}
diff --git a/Source/JavaScriptCore/wasm/js/JSWebAssemblyException.cpp b/Source/JavaScriptCore/wasm/js/JSWebAssemblyException.cpp
@@ -45,7 +45,7 @@ const ClassInfo JSWebAssemblyException::s_info = { "WebAssembly.Exception"_s, &B
 
 Structure* JSWebAssemblyException::createStructure(VM& vm, JSGlobalObject* globalObject, JSValue prototype)
 {
-    return Structure::create(vm, globalObject, prototype, TypeInfo(ErrorInstanceType, StructureFlags), info());
+    return Structure::create(vm, globalObject, prototype, TypeInfo(ObjectType, StructureFlags), info());
 }
 
 JSWebAssemblyException::JSWebAssemblyException(VM& vm, Structure* structure, Ref<const Wasm::Tag>&& tag, FixedVector<uint64_t>&& payload)

Original file line number	Diff line number	Diff line change
`@@ -45,7 +45,7 @@ const ClassInfo JSWebAssemblyException::s_info = { "WebAssembly.Exception"_s, &B`
`45`	`45`
`46`	`46`	`Structure* JSWebAssemblyException::createStructure(VM& vm, JSGlobalObject* globalObject, JSValue prototype)`
`47`	`47`	`{`
`48`		`- return Structure::create(vm, globalObject, prototype, TypeInfo(ErrorInstanceType, StructureFlags), info());`
	`48`	`+ return Structure::create(vm, globalObject, prototype, TypeInfo(ObjectType, StructureFlags), info());`
`49`	`49`	`}`
`50`	`50`
`51`	`51`	`JSWebAssemblyException::JSWebAssemblyException(VM& vm, Structure* structure, Ref<const Wasm::Tag>&& tag, FixedVector<uint64_t>&& payload)`