Zero-cost asynchronous programming in Rust
This report summarizes scanner evidence for rust-lang/futures-rs, a Rust project with 5,932 GitHub stars. SynthScan examined 47,740 lines of code across 338 source files, recording 484 pattern matches distributed across 4 syntactic categories. The legacy adjusted pattern signal is 9.4 (Moderate pattern signal); it is not an authorship estimate.
Use the findings to ask whether maintainers can explain intent, verify dependencies, simplify unnecessary scaffolding, and focus review effort. Risk Payload v1 adds ownership, supply-chain, over-engineering, and review-effort vectors when available. These are prompts for human verification, not probabilities, security findings, or measured maintenance costs.
Use each vector to guide manual verification of the underlying findings.
Can maintainers explain intent, assumptions, and trade-offs? 484 finding(s).
Are imports declared and package/API names verified? 0 finding(s).
Are wrappers, guards, and repeated structures necessary? 0 finding(s).
Which changes need focused human review? 484 finding(s).
This chart tracks the legacy adjusted pattern score across scan runs. Changes can reflect source changes, scan coverage, or detector/scoring versions; they do not measure AI adoption or prove that a team refactored code. Compare runs only when their scoring versions are compatible. The dashed line tracks the raw pattern-hit count.
Groups findings by configured severity weight. Severity is not a confidence estimate, security rating, or proof that a package is missing. Verify imports against the project's manifests and inspect each finding in its local design context.
This horizontal bar chart shows where configured pattern scores accumulate across directories. Treat the bars as locations to inspect, not as evidence of authorship or code quality. Use the file-level findings to decide whether a directory needs a focused ownership, dependency, complexity, or review check.
The scanner identified 484 distinct pattern matches across 4 syntactic categories. Each entry below represents a discrete location in the source code where the engine recorded a detector match to inspect in context. Expand any category row to inspect the individual file paths, line numbers, code snippets, and the lexical context (CODE, COMMENT, or STRING) in which each match was detected.
Reading the findings table: The Severity column indicates the configured finding weight (CRITICAL / HIGH / MEDIUM / LOW). The Context column identifies whether the match occurred inside executable code, an inline comment, or a string literal — legacy comment-context matches receive a ×1.5 score weight. The ⚡ bolt icon marks clustered matches: three or more patterns within a 10-line window, each receiving an additional ×1.5 density multiplier under the legacy scoring model.
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | futures-task/src/waker_ref.rs | 21 | impl<'a> WakerRef<'a> { | COMMENT |
| LOW | futures-task/src/future_obj.rs | 121 | impl<T> Future for FutureObj<'_, T> { | COMMENT |
| LOW | futures-task/src/future_obj.rs | 141 | /// Convert an owned instance into a (conceptually owned) fat pointer. | COMMENT |
| LOW | futures-task/src/lib.rs | 21 | #[cfg(target_has_atomic = "ptr")] | COMMENT |
| LOW | futures-task/src/noop_waker.rs | 21 | /// Create a new [`Waker`] which does | COMMENT |
| LOW | futures-task/src/spawn.rs | 1 | use core::fmt; | COMMENT |
| LOW | futures-task/src/spawn.rs | 21 | /// (but not guaranteed) to accept a subsequent spawn attempt. | COMMENT |
| LOW | futures-task/src/arc_wake.rs | 1 | use alloc::sync::Arc; | COMMENT |
| LOW | futures-task/src/arc_wake.rs | 21 | /// Indicates that the associated task is ready to make progress and should | COMMENT |
| LOW | futures-task/src/arc_wake.rs | 41 | /// Executors generally maintain a queue of "ready" tasks; `wake_by_ref` should place | COMMENT |
| LOW | futures/tests/no-std/src/lib.rs | 1 | #![cfg(nightly)] | COMMENT |
| LOW | futures/src/lib.rs | 1 | //! Abstractions for asynchronous programming. | COMMENT |
| LOW | futures/src/lib.rs | 21 | //! streams and sinks, and then spawned as independent tasks that are run to | COMMENT |
| LOW | futures/src/lib.rs | 41 | //! let fut_values = async { | COMMENT |
| LOW | futures/src/lib.rs | 61 | //! let fut_values = rx | COMMENT |
| LOW | futures/src/lib.rs | 101 | #[doc(inline)] | COMMENT |
| LOW | futures/src/lib.rs | 121 | pub use futures_util::lock; | COMMENT |
| LOW | futures/src/lib.rs | 141 | #[cfg(feature = "executor")] | COMMENT |
| LOW | futures/src/lib.rs | 161 | //! | COMMENT |
| LOW | futures/src/lib.rs | 181 | //! [`spawn_local_obj`]: https://docs.rs/futures/0.3/futures/task/trait.LocalSpawn.html#tymethod.spawn_local_obj | COMMENT |
| LOW | futures-channel/tests/oneshot.rs | 121 | orx.close(); | COMMENT |
| LOW | futures-channel/tests/oneshot.rs | 141 | // use futures::future::Either; | COMMENT |
| LOW | futures-channel/tests/oneshot.rs | 161 | // } | COMMENT |
| LOW | futures-channel/tests/oneshot.rs | 181 | // // end. | COMMENT |
| LOW | futures-channel/tests/oneshot.rs | 201 | // use std::thread; | COMMENT |
| LOW | futures-channel/tests/oneshot.rs | 221 | // Ok(Poll::Pending) | COMMENT |
| LOW | futures-channel/tests/oneshot.rs | 241 | // // forget the spawned future: should keep running, i.e. hit | COMMENT |
| LOW | futures-channel/tests/mpsc.rs | 141 | })); | COMMENT |
| LOW | futures-channel/tests/mpsc.rs | 161 | // // responding), but dropping it leads to observable side effects | COMMENT |
| LOW | futures-channel/tests/mpsc.rs | 181 | // thread::spawn(move || { | COMMENT |
| LOW | futures-channel/src/oneshot.rs | 41 | /// Indicates whether this oneshot is complete yet. This is filled in both | COMMENT |
| LOW | futures-channel/src/oneshot.rs | 61 | /// Field to store the task which is blocked in `Receiver::poll`. | COMMENT |
| LOW | futures-channel/src/oneshot.rs | 81 | /// half is a `Receiver` which implements the `Future` trait, resolving to the | COMMENT |
| LOW | futures-channel/src/oneshot.rs | 161 | // destructor, but our destructor hasn't run yet so if it's set then the | COMMENT |
| LOW | futures-channel/src/oneshot.rs | 201 | // 2. The receiver is being dropped | COMMENT |
| LOW | futures-channel/src/oneshot.rs | 301 | // Indicate to the `Sender` that we're done, so any future calls to | COMMENT |
| LOW | futures-channel/src/oneshot.rs | 341 | pub fn send(self, t: T) -> Result<(), T> { | COMMENT |
| LOW | futures-channel/src/oneshot.rs | 361 | /// Creates a future that resolves when this `Sender`'s corresponding | COMMENT |
| LOW | futures-channel/src/lib.rs | 1 | //! Asynchronous channels. | COMMENT |
| LOW | futures-channel/src/mpsc/queue.rs | 21 | * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | COMMENT |
| LOW | futures-channel/src/mpsc/queue.rs | 101 | let prev = self.head.swap(n, Ordering::AcqRel); | COMMENT |
| LOW | futures-channel/src/mpsc/queue.rs | 141 | loop { | COMMENT |
| LOW | futures-channel/src/mpsc/mod.rs | 1 | //! A multi-producer, single-consumer queue for sending values across | COMMENT |
| LOW | futures-channel/src/mpsc/mod.rs | 21 | //! | COMMENT |
| LOW | futures-channel/src/mpsc/mod.rs | 41 | // At the core, the channel uses an atomic FIFO queue for message passing. This | COMMENT |
| LOW | futures-channel/src/mpsc/mod.rs | 61 | // message that caused the sender to become parked is read out of the channel. | COMMENT |
| LOW | futures-channel/src/mpsc/mod.rs | 1021 | // Wake up any threads waiting as they'll see that we've closed the | COMMENT |
| LOW | futures-channel/src/mpsc/mod.rs | 1241 | /// It is not recommended to call this function from inside of a future, | COMMENT |
| LOW | futures-executor/src/thread_pool.rs | 21 | /// A general-purpose thread pool for scheduling tasks that poll futures to | COMMENT |
| LOW | futures-executor/src/thread_pool.rs | 81 | impl ThreadPool { | COMMENT |
| LOW | futures-executor/src/thread_pool.rs | 101 | /// > it is guaranteed to always succeed. | COMMENT |
| LOW | futures-executor/src/thread_pool.rs | 221 | /// Thread name prefix is used for generating thread names. For example, if prefix is | COMMENT |
| LOW | futures-executor/src/lib.rs | 1 | //! Built-in executors and related tools. | COMMENT |
| LOW | futures-executor/src/lib.rs | 21 | //! directly. In the case of `!Send` futures, [`spawn_local_obj`] can be used | COMMENT |
| LOW | futures-executor/src/lib.rs | 61 | #[cfg_attr(docsrs, doc(cfg(feature = "thread-pool")))] | COMMENT |
| LOW | futures-executor/src/unpark_mutex.rs | 21 | // re-polling. | COMMENT |
| LOW | futures-executor/src/enter.rs | 41 | /// | COMMENT |
| LOW | futures-executor/src/local_pool.rs | 21 | COMMENT | |
| LOW | futures-executor/src/local_pool.rs | 121 | LocalSpawner { incoming: Rc::downgrade(&self.incoming) } | COMMENT |
| LOW | futures-executor/src/local_pool.rs | 141 | } | COMMENT |
| 418 more matches not shown… | ||||
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| MEDIUM | futures/tests/async_await_macros.rs | 348 | // This test may be a bit flaky. Feel free to adjust the margins as you see fit. | COMMENT |
| MEDIUM | futures-core/src/task/__internal/atomic_waker.rs | 40 | /// Here is a simple example providing a `Flag` that can be signalled manually | COMMENT |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | futures-channel/src/mpsc/mod.rs | 640 | /// # Return value | COMMENT |
| LOW | futures-channel/src/mpsc/mod.rs | 740 | /// # Return value | COMMENT |
| LOW | futures-core/src/stream.rs | 47 | /// # Return value | COMMENT |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| MEDIUM | futures-util/src/io/line_writer.rs | 19 | /// Buffering is actually done using `BufWriter`. This class will leverage `BufWriter` | COMMENT |