Add 'activeParameter' to SignatureInformation

_specifications/specification-3-16.md

@@ -3726,6 +3726,14 @@ export interface SignatureHelpClientCapabilities {
 			 */
 			labelOffsetSupport?: boolean;
 		};
+
+		/**
+		 * The client support the `activeParameter` property on `SignatureInformation`
+		 * literal.
+		 *
+		 * @since 3.16.0 - proposed state
+		 */
+		activeParameterSupport?: boolean;
 	};
 
 	/**
@@ -3905,6 +3913,15 @@ export interface SignatureInformation {
 	 * The parameters of this signature.
 	 */
 	parameters?: ParameterInformation[];
+
+	/**
+	 * The index of the active parameter.
+	 *
+	 * If provided, this is used in place of `SignatureHelp.activeSignature`.
+	 *
+	 * @since 3.16.0 - proposed state
+	 */
+	activeParameter?: number;
 }
 
 /**