use cli.canSupport to determine intentional mentions support (#3445)

* use cli.canSupport to determine intentional mentions support

* more specific comment

* Update src/client.ts

Co-authored-by: Michael Telatynski <7t3chguy@gmail.com>

---------

Co-authored-by: Michael Telatynski <7t3chguy@gmail.com>

src/client.ts

@@ -469,11 +469,6 @@ export interface IStartClientOpts {
      * @experimental
      */
     slidingSync?: SlidingSync;
-
-    /**
-     * @experimental
-     */
-    intentionalMentions?: boolean;
 }
 
 export interface IStoredClientOpts extends IStartClientOpts {}
@@ -9635,11 +9630,11 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
 
     /**
      * A helper to determine intentional mentions support
-     * @returns a boolean to determine if intentional mentions are enabled
+     * @returns a boolean to determine if intentional mentions are enabled on the server
      * @experimental
      */
     public supportsIntentionalMentions(): boolean {
-        return this.clientOpts?.intentionalMentions || false;
+        return this.canSupport.get(Feature.IntentionalMentions) !== ServerSupport.Unsupported;
     }
 
     /**

src/feature.ts

@@ -32,6 +32,7 @@ export enum Feature {
     RelationBasedRedactions = "RelationBasedRedactions",
     AccountDataDeletion = "AccountDataDeletion",
     RelationsRecursion = "RelationsRecursion",
+    IntentionalMentions = "IntentionalMentions",
 }
 
 type FeatureSupportCondition = {
@@ -60,6 +61,9 @@ const featureSupportResolver: Record<string, FeatureSupportCondition> = {
     [Feature.RelationsRecursion]: {
         unstablePrefixes: ["org.matrix.msc3981"],
     },
+    [Feature.IntentionalMentions]: {
+        unstablePrefixes: ["org.matrix.msc3952_intentional_mentions"],
+    },
 };
 
 export async function buildFeatureSupportMap(versions: IServerVersions): Promise<Map<Feature, ServerSupport>> {