fix(mdx-loader): make headings containing links properly formatted in…

… ToC (#6712)

packages/docusaurus-mdx-loader/src/remark/utils/index.ts

@@ -8,31 +8,29 @@
 import escapeHtml from 'escape-html';
 import toString from 'mdast-util-to-string';
 import type {Parent} from 'unist';
-import type {StaticPhrasingContent, Heading} from 'mdast';
+import type {PhrasingContent, Heading} from 'mdast';
 
 export function stringifyContent(node: Parent): string {
-  return ((node.children || []) as StaticPhrasingContent[])
-    .map(toValue)
-    .join('');
+  return ((node.children || []) as PhrasingContent[]).map(toValue).join('');
 }
 
-export function toValue(node: StaticPhrasingContent | Heading): string {
-  if (node && node.type) {
-    switch (node.type) {
-      case 'text':
-        return escapeHtml(node.value);
-      case 'heading':
-        return stringifyContent(node);
-      case 'inlineCode':
-        return `<code>${escapeHtml(node.value)}</code>`;
-      case 'emphasis':
-        return `<em>${stringifyContent(node)}</em>`;
-      case 'strong':
-        return `<strong>${stringifyContent(node)}</strong>`;
-      case 'delete':
-        return `<del>${stringifyContent(node)}</del>`;
-      default:
-    }
+export function toValue(node: PhrasingContent | Heading): string {
+  switch (node?.type) {
+    case 'text':
+      return escapeHtml(node.value);
+    case 'heading':
+      return stringifyContent(node);
+    case 'inlineCode':
+      return `<code>${escapeHtml(node.value)}</code>`;
+    case 'emphasis':
+      return `<em>${stringifyContent(node)}</em>`;
+    case 'strong':
+      return `<strong>${stringifyContent(node)}</strong>`;
+    case 'delete':
+      return `<del>${stringifyContent(node)}</del>`;
+    case 'link':
+      return stringifyContent(node);
+    default:
   }
 
   return toString(node);