TryRecvError

TryRecvError is an error type used by Rust’s channel primitives to signal the outcome of a non-blocking receive operation. It appears when attempting to retrieve a message without waiting, via the try_recv method on a channel’s receiver. The type is commonly found as std::sync::mpsc::TryRecvError in the standard library, and similar variants exist in other channel implementations such as crossbeam.

The TryRecvError enum has two variants: Empty and Disconnected. Empty indicates that no message is currently available in the channel, but the channel is still open and additional messages may arrive in the future. Disconnected indicates that all sending ends have been dropped and the channel is closed; in this case there will be no further values to receive. These variants help callers distinguish between a temporarily empty channel and a permanently closed one.

In practice, try_recv returns a Result<T, TryRecvError>. A successful Ok(value) means a message was retrieved immediately. An Err(TryRecvError::Empty) suggests that the operation would block if a value were required now, while Err(TryRecvError::Disconnected) signals that no more messages will ever arrive from the channel. This non-blocking API contrasts with recv, which blocks until a value is available or the channel is closed and returns a different error type (e.g., RecvError) upon closure.

Related concepts include TrySend and Recv, which cover non-blocking sends and blocking receives, respectively. TryRecvError is a concise way to communicate channel readiness in non-blocking receive patterns.