fix: have isClosed check if sender is closed

src/sync/mpsc.ts

@@ -185,7 +185,7 @@ export class Sender<T> {
 	}
 
 	isClosed(): boolean {
-		return this.#state.closed;
+		return this.#dropped || this.#state.closed;
 	}
 
 	capacity(): number {
@@ -373,7 +373,7 @@ export class UnboundedSender<T> {
 	}
 
 	isClosed(): boolean {
-		return this.#state.closed;
+		return this.#dropped || this.#state.closed;
 	}
 
 	clone(): UnboundedSender<T> {

src/sync/oneshot.ts

@@ -70,7 +70,7 @@ export class OneshotSender<T> {
 	}
 
 	isClosed(): boolean {
-		return this.#state.receiverClosed;
+		return this.#dropped || this.#state.receiverClosed;
 	}
 
 	closed(signal?: AbortSignal): Promise<void> {

src/sync/watch.ts

@@ -89,7 +89,7 @@ export class WatchSender<T> {
 	}
 
 	isClosed(): boolean {
-		return this.#state.receiverCount === 0;
+		return this.#closed || this.#state.receiverCount === 0;
 	}
 
 	close(): void {

tests/sync/mpsc.test.ts

@@ -145,6 +145,13 @@ describe("bounded channel", () => {
 		expect(tx.isClosed()).toBe(true);
 	});
 
+	it("isClosed is true after sender close", () => {
+		const [tx, rx] = channel<number>(8);
+		tx.close();
+		expect(tx.isClosed()).toBe(true);
+		void rx;
+	});
+
 	it("closed() resolves when receiver closes", async () => {
 		const [tx, rx] = channel<number>(8);
 		let resolved = false;
@@ -512,6 +519,13 @@ describe("unbounded channel", () => {
 		expect(tx.isClosed()).toBe(true);
 	});
 
+	it("isClosed is true after sender close", () => {
+		const [tx, rx] = unboundedChannel<number>();
+		tx.close();
+		expect(tx.isClosed()).toBe(true);
+		void rx;
+	});
+
 	it("closed() resolves when receiver closes", async () => {
 		const [tx, rx] = unboundedChannel<number>();
 		let resolved = false;

tests/sync/oneshot.test.ts

@@ -205,6 +205,13 @@ describe("oneshot", () => {
 		expect(tx.isClosed()).toBe(true);
 	});
 
+	it("isClosed is true after sender close", () => {
+		const [tx, rx] = oneshot<number>();
+		tx[Symbol.dispose]();
+		expect(tx.isClosed()).toBe(true);
+		void rx;
+	});
+
 	it("isClosed is false after send (sender closed but receiver is not)", () => {
 		const [tx, rx] = oneshot<number>();
 		tx.send(1);

tests/sync/watch.test.ts

@@ -105,6 +105,13 @@ describe("watch", () => {
 		expect(tx.isClosed()).toBe(true);
 	});
 
+	it("isClosed is true after sender close", () => {
+		const [tx, rx] = watch(0);
+		tx.close();
+		expect(tx.isClosed()).toBe(true);
+		void rx;
+	});
+
 	it("sendIfModified returns true and wakes receivers when predicate returns true", async () => {
 		const [tx, rx] = watch({ count: 0 });
 		rx.borrowAndUpdate();