85 lines
2.4 KiB
Rust
85 lines
2.4 KiB
Rust
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use clippy_utils::{diagnostics::span_lint_and_sugg, source::snippet};
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use rustc_ast::ast::*;
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use rustc_ast::visit::Visitor as AstVisitor;
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use rustc_errors::Applicability;
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use rustc_lint::{EarlyContext, EarlyLintPass};
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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
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/// Checks for `async` block that only returns `await` on a future.
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///
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/// ### Why is this bad?
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/// It is simpler and more efficient to use the future directly.
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///
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/// ### Example
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/// ```rust
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/// async fn f() -> i32 {
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/// 1 + 2
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/// }
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///
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/// let fut = async {
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/// f().await
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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 f() -> i32 {
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/// 1 + 2
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/// }
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///
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/// let fut = f();
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/// ```
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#[clippy::version = "1.69.0"]
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pub REDUNDANT_ASYNC_BLOCK,
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complexity,
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"`async { future.await }` can be replaced by `future`"
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}
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declare_lint_pass!(RedundantAsyncBlock => [REDUNDANT_ASYNC_BLOCK]);
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impl EarlyLintPass for RedundantAsyncBlock {
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fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
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if expr.span.from_expansion() {
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return;
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}
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if let ExprKind::Async(_, _, block) = &expr.kind && block.stmts.len() == 1 &&
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let Some(Stmt { kind: StmtKind::Expr(last), .. }) = block.stmts.last() &&
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let ExprKind::Await(future) = &last.kind &&
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!future.span.from_expansion() &&
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!await_in_expr(future)
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{
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span_lint_and_sugg(
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cx,
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REDUNDANT_ASYNC_BLOCK,
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expr.span,
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"this async expression only awaits a single future",
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"you can reduce it to",
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snippet(cx, future.span, "..").into_owned(),
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Applicability::MachineApplicable,
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);
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}
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}
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}
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/// Check whether an expression contains `.await`
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fn await_in_expr(expr: &Expr) -> bool {
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let mut detector = AwaitDetector::default();
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detector.visit_expr(expr);
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detector.await_found
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}
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#[derive(Default)]
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struct AwaitDetector {
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await_found: bool,
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}
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impl<'ast> AstVisitor<'ast> for AwaitDetector {
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fn visit_expr(&mut self, ex: &'ast Expr) {
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match (&ex.kind, self.await_found) {
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(ExprKind::Await(_), _) => self.await_found = true,
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(_, false) => rustc_ast::visit::walk_expr(self, ex),
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_ => (),
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}
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}
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}
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