88 lines
3.2 KiB
Rust
88 lines
3.2 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_then;
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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::{AsyncGeneratorKind, Body, BodyId, ExprKind, GeneratorKind, QPath};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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declare_clippy_lint! {
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/// **What it does:** Checks for async blocks that yield values of types
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/// that can themselves be awaited.
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///
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/// **Why is this bad?** An await is likely missing.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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///
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/// ```rust
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/// async fn foo() {}
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///
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/// fn bar() {
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/// let x = async {
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/// foo()
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/// };
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/// }
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/// ```
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/// Use instead:
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/// ```rust
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/// async fn foo() {}
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///
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/// fn bar() {
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/// let x = async {
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/// foo().await
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/// };
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/// }
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/// ```
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pub ASYNC_YIELDS_ASYNC,
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correctness,
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"async blocks that return a type that can be awaited"
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}
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declare_lint_pass!(AsyncYieldsAsync => [ASYNC_YIELDS_ASYNC]);
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impl<'tcx> LateLintPass<'tcx> for AsyncYieldsAsync {
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fn check_body(&mut self, cx: &LateContext<'tcx>, body: &'tcx Body<'_>) {
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use AsyncGeneratorKind::{Block, Closure};
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// For functions, with explicitly defined types, don't warn.
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// XXXkhuey maybe we should?
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if let Some(GeneratorKind::Async(Block | Closure)) = body.generator_kind {
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if let Some(future_trait_def_id) = cx.tcx.lang_items().future_trait() {
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let body_id = BodyId {
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hir_id: body.value.hir_id,
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};
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let typeck_results = cx.tcx.typeck_body(body_id);
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let expr_ty = typeck_results.expr_ty(&body.value);
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if implements_trait(cx, expr_ty, future_trait_def_id, &[]) {
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let return_expr_span = match &body.value.kind {
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// XXXkhuey there has to be a better way.
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ExprKind::Block(block, _) => block.expr.map(|e| e.span),
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ExprKind::Path(QPath::Resolved(_, path)) => Some(path.span),
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_ => None,
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};
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if let Some(return_expr_span) = return_expr_span {
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span_lint_and_then(
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cx,
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ASYNC_YIELDS_ASYNC,
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return_expr_span,
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"an async construct yields a type which is itself awaitable",
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|db| {
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db.span_label(body.value.span, "outer async construct");
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db.span_label(return_expr_span, "awaitable value not awaited");
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db.span_suggestion(
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return_expr_span,
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"consider awaiting this value",
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format!("{}.await", snippet(cx, return_expr_span, "..")),
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Applicability::MaybeIncorrect,
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);
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},
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);
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}
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}
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}
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}
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}
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}
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