fix: embedding splicer error handling

This commit fixes a regression in function generation when error
handling is involved.

The buggy code over-eagerly checks whether there is an error type
type present on a result, when there may legitimately not
be (e.g. `result<t>` in WIT). The fix is to check *only* for whether
the types are returned as a pair (indicating a `result`) at all.

Author: vados-cosmonic

crates/spidermonkey-embedding-splicer/src/bindgen.rs

@@ -859,15 +859,13 @@ impl JsBindgen<'_> {
             }
         }
 
-        let err = if get_result_types(self.resolve, func.result)
-            .is_some_and(|(_, err_ty)| err_ty.is_some())
-        {
+        let err = if get_result_types(self.resolve, func.result).is_some() {
             match abi {
                 AbiVariant::GuestExport => ErrHandling::ThrowResultErr,
                 AbiVariant::GuestImport => ErrHandling::ResultCatchHandler,
-                AbiVariant::GuestImportAsync => todo!(),
-                AbiVariant::GuestExportAsync => todo!(),
-                AbiVariant::GuestExportAsyncStackful => todo!(),
+                AbiVariant::GuestImportAsync
+                | AbiVariant::GuestExportAsync
+                | AbiVariant::GuestExportAsyncStackful => todo!(),
             }
         } else {
             ErrHandling::None

test/cases/http-server/source.js

@@ -9,9 +9,9 @@ import {
 export const incomingHandler = {
   handle(incomingRequest, responseOutparam) {
     const outgoingResponse = new OutgoingResponse(new Fields());
-    let outgoingBody = outgoingResponse.body().val;
+    let outgoingBody = outgoingResponse.body();
     {
-      let outputStream = outgoingBody.write().val;
+      let outputStream = outgoingBody.write();
       outputStream.blockingWriteAndFlush(
         new Uint8Array(new TextEncoder().encode('Hello world!')),
       );