bb93c23c08
the behavior of the type system not only depends on the current assumptions, but also the currentnphase of the compiler. This is mostly necessary as we need to decide whether and how to reveal opaque types. We track this via the `TypingMode`.
81 lines
2.7 KiB
Rust
81 lines
2.7 KiB
Rust
use clippy_config::Conf;
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use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::source::snippet;
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use clippy_utils::ty::implements_trait;
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use rustc_errors::Applicability;
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use rustc_hir::{Expr, ExprKind, LangItem, MatchSource, QPath};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::impl_lint_pass;
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use rustc_target::abi::Size;
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declare_clippy_lint! {
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/// ### What it does
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/// It checks for the size of a `Future` created by `async fn` or `async {}`.
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///
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/// ### Why is this bad?
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/// Due to the current [unideal implementation](https://github.com/rust-lang/rust/issues/69826) of `Coroutine`,
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/// large size of a `Future` may cause stack overflows.
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///
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/// ### Example
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/// ```no_run
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/// async fn large_future(_x: [u8; 16 * 1024]) {}
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///
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/// pub async fn trigger() {
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/// large_future([0u8; 16 * 1024]).await;
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/// }
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/// ```
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///
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/// `Box::pin` the big future instead.
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///
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/// ```no_run
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/// async fn large_future(_x: [u8; 16 * 1024]) {}
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///
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/// pub async fn trigger() {
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/// Box::pin(large_future([0u8; 16 * 1024])).await;
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/// }
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/// ```
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#[clippy::version = "1.70.0"]
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pub LARGE_FUTURES,
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pedantic,
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"large future may lead to unexpected stack overflows"
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}
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pub struct LargeFuture {
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future_size_threshold: u64,
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}
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impl LargeFuture {
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pub fn new(conf: &'static Conf) -> Self {
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Self {
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future_size_threshold: conf.future_size_threshold,
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}
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}
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}
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impl_lint_pass!(LargeFuture => [LARGE_FUTURES]);
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impl<'tcx> LateLintPass<'tcx> for LargeFuture {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
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if let ExprKind::Match(scrutinee, _, MatchSource::AwaitDesugar) = expr.kind
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&& let ExprKind::Call(func, [arg]) = scrutinee.kind
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&& let ExprKind::Path(QPath::LangItem(LangItem::IntoFutureIntoFuture, ..)) = func.kind
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&& !expr.span.from_expansion()
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&& let ty = cx.typeck_results().expr_ty(arg)
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&& let Some(future_trait_def_id) = cx.tcx.lang_items().future_trait()
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&& implements_trait(cx, ty, future_trait_def_id, &[])
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&& let Ok(layout) = cx.tcx.layout_of(cx.typing_env().as_query_input(ty))
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&& let size = layout.layout.size()
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&& size >= Size::from_bytes(self.future_size_threshold)
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{
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span_lint_and_sugg(
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cx,
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LARGE_FUTURES,
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arg.span,
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format!("large future with a size of {} bytes", size.bytes()),
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"consider `Box::pin` on it",
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format!("Box::pin({})", snippet(cx, arg.span, "..")),
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Applicability::Unspecified,
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);
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}
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}
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}
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