1 use if_chain::if_chain;
2 use rustc_errors::Applicability;
3 use rustc_hir::{BinOpKind, Expr, ExprKind};
4 use rustc_lint::{LateContext, LateLintPass};
5 use rustc_session::{declare_lint_pass, declare_tool_lint};
6 use rustc_span::source_map::Spanned;
8 use crate::consts::{constant, Constant};
9 use crate::utils::paths;
10 use crate::utils::{match_type, snippet_with_applicability, span_lint_and_sugg, walk_ptrs_ty};
12 declare_clippy_lint! {
13 /// **What it does:** Checks for calculation of subsecond microseconds or milliseconds
14 /// from other `Duration` methods.
16 /// **Why is this bad?** It's more concise to call `Duration::subsec_micros()` or
17 /// `Duration::subsec_millis()` than to calculate them.
19 /// **Known problems:** None.
23 /// # use std::time::Duration;
24 /// let dur = Duration::new(5, 0);
25 /// let _micros = dur.subsec_nanos() / 1_000;
26 /// let _millis = dur.subsec_nanos() / 1_000_000;
30 "checks for calculation of subsecond microseconds or milliseconds"
33 declare_lint_pass!(DurationSubsec => [DURATION_SUBSEC]);
35 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for DurationSubsec {
36 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
38 if let ExprKind::Binary(Spanned { node: BinOpKind::Div, .. }, ref left, ref right) = expr.kind;
39 if let ExprKind::MethodCall(ref method_path, _ , ref args) = left.kind;
40 if match_type(cx, walk_ptrs_ty(cx.tables.expr_ty(&args[0])), &paths::DURATION);
41 if let Some((Constant::Int(divisor), _)) = constant(cx, cx.tables, right);
43 let suggested_fn = match (method_path.ident.as_str().as_ref(), divisor) {
44 ("subsec_micros", 1_000) | ("subsec_nanos", 1_000_000) => "subsec_millis",
45 ("subsec_nanos", 1_000) => "subsec_micros",
48 let mut applicability = Applicability::MachineApplicable;
53 &format!("Calling `{}()` is more concise than this calculation", suggested_fn),
57 snippet_with_applicability(cx, args[0].span, "_", &mut applicability),