Replace invalid import attributes assertion

When creating a module script, there is no guarantee yet that the
module's dependencies only have valid import attribute keys. Instead
of asserting that only `type` is used, this commit introduces proper
validation throwing a SyntaxError.

source

@@ -3034,6 +3034,7 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
      <li>The <dfn data-x-href="https://tc39.es/ecma262/#sec-finalization-registry-objects"><code>FinalizationRegistry</code></dfn> class</li>
      <li>The <dfn data-x-href="https://tc39.es/ecma262/#sec-regexp-regular-expression-objects"><code>RegExp</code></dfn> class</li>
      <li>The <dfn data-x-href="https://tc39.es/ecma262/#sec-sharedarraybuffer-objects"><code>SharedArrayBuffer</code></dfn> class</li>
+     <li>The <dfn data-x-href="https://tc39.es/ecma262/#sec-native-error-types-used-in-this-standard-syntaxerror"><code>SyntaxError</code></dfn> class</li>
      <li>The <dfn data-x-href="https://tc39.es/ecma262/#sec-native-error-types-used-in-this-standard-typeerror"><code>TypeError</code></dfn> class</li>
      <li>The <dfn data-x="js-RangeError" data-x-href="https://tc39.es/ecma262/#sec-native-error-types-used-in-this-standard-rangeerror"><code>RangeError</code></dfn> class</li>
      <li>The <dfn data-x-href="https://tc39.es/ecma262/#sec-weak-ref-objects"><code>WeakRef</code></dfn> class</li>
@@ -103790,6 +103791,27 @@ document.querySelector("button").addEventListener("click", bound);
     <var>requested</var> of <var>result</var>.[[RequestedModules]]:</p>
 
     <ol>
+     <li>
+      <p>If <var>requested</var>.[[Attributes]] contains a <span>Record</span> <var>entry</var>
+      such that <var>entry</var>.[[Key]] is not "<code data-x="">type</code>", then:</p>
+
+      <ol>
+       <li><p>Let <var>error</var> be a new <code>SyntaxError</code> exception.</p></li>
+
+       <li><p>Set <var>script</var>'s <span data-x="concept-script-parse-error">parse error</span>
+       to <var>error</var>.</p></li>
+
+       <li><p>Return <var>script</var>.</p></li>
+      </ol>
+
+      <p class="note">The JavaScript specification re-performs this validation when lodaing
+      <var>script</var>'s dependencies. It is duplicated here to skip unnecessary work given that,
+      in case of an invalid attribute key, loading the module graph would fail so we can
+      exit early and skip unnecessary work. Additionally, this makes the errors reported for invalid
+      static imports consistent with dynamic imports, for which invalid attributes are reported
+      before calling into HTML and thus before validating the imported specifier.</p>
+     </li>
+
      <li><p>Let <var>url</var> be the result of <span data-x="resolve a module specifier">resolving
      a module specifier</span> given <var>script</var> and
      <var>requested</var>.[[Specifier]], catching any exceptions.</p></li>