Fix $.update and $.update_pre for bigints

packages/svelte/src/internal/client/runtime.js

@@ -972,23 +972,43 @@ function get_parent_context(component_context) {
 }
 
 /**
- * @param {Value<number>} signal
+ * @template {number|bigint} T
+ * @param {Value<T>} signal
  * @param {1 | -1} [d]
- * @returns {number}
+ * @returns {T}
  */
 export function update(signal, d = 1) {
-	var value = +get(signal);
-	set(signal, value + d);
+	var value = get(signal);
+
+	if(typeof value === "bigint") {
+		//@ts-ignore
+		set(signal, value + BigInt(d));
+	}else {
+		//@ts-ignore
+		set(signal, +value + d);
+	}
+
 	return value;
 }
 
 /**
- * @param {Value<number>} signal
+ * @template {number|bigint} T
+ * @param {Value<T>} signal
  * @param {1 | -1} [d]
- * @returns {number}
+ * @returns {T}
  */
 export function update_pre(signal, d = 1) {
-	return set(signal, +get(signal) + d);
+	var value = get(signal);
+
+	if(typeof value === "bigint") {
+		//@ts-ignore
+		d = BigInt(d);
+	}else {
+		//@ts-ignore
+		value = +value;
+	}
+	//@ts-ignore
+	return set(signal, value + d);
 }
 
 /**

packages/svelte/tests/signals/test.ts

@@ -739,4 +739,20 @@ describe('signals', () => {
 			assert.deepEqual(a.reactions, null);
 		};
 	});
+
+	test('bigint states update correctly', () => {
+		return () => {
+			const count = state(0n);
+
+			assert.doesNotThrow(() => $.update(count));
+			assert.equal($.get(count), 1n);
+			assert.doesNotThrow(() => $.update(count, -1));
+			assert.equal($.get(count), 0n);
+
+			assert.doesNotThrow(() => $.update_pre(count));
+			assert.equal($.get(count), 1n);
+			assert.doesNotThrow(() => $.update_pre(count, -1));
+			assert.equal($.get(count), 0n);
+		}
+	})
 });