Fix conversions.ArrayBuffer with allowShared not accepting a SharedArrayBuffer

Author: MattiasBuelens

lib/index.js

@@ -338,10 +338,13 @@ function isArrayBufferDetached(value) {
 
 exports.ArrayBuffer = (value, options = {}) => {
   if (!isNonSharedArrayBuffer(value)) {
-    if (options.allowShared && !isSharedArrayBuffer(value)) {
-      throw makeException(TypeError, "is not an ArrayBuffer or SharedArrayBuffer", options);
+    if (options.allowShared) {
+      if (!isSharedArrayBuffer(value)) {
+        throw makeException(TypeError, "is not an ArrayBuffer or SharedArrayBuffer", options);
+      }
+    } else {
+      throw makeException(TypeError, "is not an ArrayBuffer", options);
     }
-    throw makeException(TypeError, "is not an ArrayBuffer", options);
   }
   if (isArrayBufferDetached(value)) {
     throw makeException(TypeError, "is a detached ArrayBuffer", options);

test/buffer-source.js

@@ -211,7 +211,11 @@ for (const type of bufferSourceConstructors) {
       const allowSharedSUT = (v, opts) => conversions[typeName](v, { ...opts, allowShared: true });
 
       for (const { label, creator, typeName: innerTypeName, isDetached, isForged } of bufferSourceCreators) {
-        const testFunction = innerTypeName === typeName && !isDetached && !isForged ? testOk : testNotOk;
+        const testFunction = (
+            innerTypeName === typeName || (innerTypeName === "SharedArrayBuffer" && typeName === "ArrayBuffer")
+          ) && !isDetached && !isForged ?
+            testOk :
+            testNotOk;
         testFunction(label, allowSharedSUT, creator);
       }