1 use clippy_utils::source::snippet_with_applicability;
2 use clippy_utils::ty::match_type;
3 use if_chain::if_chain;
4 use rustc_errors::Applicability;
5 use rustc_hir::{BinOpKind, Expr, ExprKind};
6 use rustc_lint::{LateContext, LateLintPass};
7 use rustc_session::{declare_lint_pass, declare_tool_lint};
8 use rustc_span::source_map::Spanned;
10 use clippy_utils::consts::{constant, Constant};
11 use clippy_utils::diagnostics::span_lint_and_sugg;
12 use clippy_utils::paths;
14 declare_clippy_lint! {
16 /// Checks for calculation of subsecond microseconds or milliseconds
17 /// from other `Duration` methods.
19 /// ### Why is this bad?
20 /// It's more concise to call `Duration::subsec_micros()` or
21 /// `Duration::subsec_millis()` than to calculate them.
25 /// # use std::time::Duration;
26 /// let dur = Duration::new(5, 0);
29 /// let _micros = dur.subsec_nanos() / 1_000;
30 /// let _millis = dur.subsec_nanos() / 1_000_000;
33 /// let _micros = dur.subsec_micros();
34 /// let _millis = dur.subsec_millis();
36 #[clippy::version = "pre 1.29.0"]
39 "checks for calculation of subsecond microseconds or milliseconds"
42 declare_lint_pass!(DurationSubsec => [DURATION_SUBSEC]);
44 impl<'tcx> LateLintPass<'tcx> for DurationSubsec {
45 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
47 if let ExprKind::Binary(Spanned { node: BinOpKind::Div, .. }, left, right) = expr.kind;
48 if let ExprKind::MethodCall(method_path, _ , args, _) = left.kind;
49 if match_type(cx, cx.typeck_results().expr_ty(&args[0]).peel_refs(), &paths::DURATION);
50 if let Some((Constant::Int(divisor), _)) = constant(cx, cx.typeck_results(), right);
52 let suggested_fn = match (method_path.ident.as_str().as_ref(), divisor) {
53 ("subsec_micros", 1_000) | ("subsec_nanos", 1_000_000) => "subsec_millis",
54 ("subsec_nanos", 1_000) => "subsec_micros",
57 let mut applicability = Applicability::MachineApplicable;
62 &format!("calling `{}()` is more concise than this calculation", suggested_fn),
66 snippet_with_applicability(cx, args[0].span, "_", &mut applicability),