Enable @typescript-eslint/explicit-function-return-type in /src (#9788)

* Enable `@typescript-eslint/explicit-member-accessibility` on /src

* Prettier

* Enable `@typescript-eslint/explicit-function-return-type` in /src

* Fix types

* tsc strict fixes

* Delint

* Fix test

* Fix bad merge

src/notifications/ContentRules.ts

@@ -92,7 +92,9 @@ export class ContentRules {
         }
     }
 
-    private static categoriseContentRules(rulesets: IPushRules) {
+    private static categoriseContentRules(
+        rulesets: IPushRules,
+    ): Record<"on" | "on_but_disabled" | "loud" | "loud_but_disabled" | "other", IAnnotatedPushRule[]> {
         const contentRules: Record<
             "on" | "on_but_disabled" | "loud" | "loud_but_disabled" | "other",
             IAnnotatedPushRule[]

src/notifications/PushRuleVectorState.ts

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import { IPushRule } from "matrix-js-sdk/src/@types/PushRules";
+import { IPushRule, PushRuleAction } from "matrix-js-sdk/src/@types/PushRules";
 
 import { StandardActions } from "./StandardActions";
 import { NotificationUtils } from "./NotificationUtils";
@@ -47,7 +47,7 @@ export class PushRuleVectorState {
      *
      * @return [object] list of push-rule actions
      */
-    public static actionsFor(pushRuleVectorState: VectorState) {
+    public static actionsFor(pushRuleVectorState: VectorState): PushRuleAction[] {
         if (pushRuleVectorState === VectorState.On) {
             return StandardActions.ACTION_NOTIFY;
         } else if (pushRuleVectorState === VectorState.Loud) {