rust-clippy/clippy_lints/src/duration_subsec.rs

75 lines
2.9 KiB
Rust

use clippy_utils::consts::{constant, Constant};
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::snippet_with_applicability;
use clippy_utils::ty::is_type_diagnostic_item;
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::{BinOpKind, Expr, ExprKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::source_map::Spanned;
use rustc_span::sym;
declare_clippy_lint! {
/// ### What it does
/// Checks for calculation of subsecond microseconds or milliseconds
/// from other `Duration` methods.
///
/// ### Why is this bad?
/// It's more concise to call `Duration::subsec_micros()` or
/// `Duration::subsec_millis()` than to calculate them.
///
/// ### Example
/// ```rust
/// # use std::time::Duration;
/// # let duration = Duration::new(5, 0);
/// let micros = duration.subsec_nanos() / 1_000;
/// let millis = duration.subsec_nanos() / 1_000_000;
/// ```
///
/// Use instead:
/// ```rust
/// # use std::time::Duration;
/// # let duration = Duration::new(5, 0);
/// let micros = duration.subsec_micros();
/// let millis = duration.subsec_millis();
/// ```
#[clippy::version = "pre 1.29.0"]
pub DURATION_SUBSEC,
complexity,
"checks for calculation of subsecond microseconds or milliseconds"
}
declare_lint_pass!(DurationSubsec => [DURATION_SUBSEC]);
impl<'tcx> LateLintPass<'tcx> for DurationSubsec {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if_chain! {
if let ExprKind::Binary(Spanned { node: BinOpKind::Div, .. }, left, right) = expr.kind;
if let ExprKind::MethodCall(method_path, args, _) = left.kind;
if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&args[0]).peel_refs(), sym::Duration);
if let Some((Constant::Int(divisor), _)) = constant(cx, cx.typeck_results(), right);
then {
let suggested_fn = match (method_path.ident.as_str(), divisor) {
("subsec_micros", 1_000) | ("subsec_nanos", 1_000_000) => "subsec_millis",
("subsec_nanos", 1_000) => "subsec_micros",
_ => return,
};
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
DURATION_SUBSEC,
expr.span,
&format!("calling `{}()` is more concise than this calculation", suggested_fn),
"try",
format!(
"{}.{}()",
snippet_with_applicability(cx, args[0].span, "_", &mut applicability),
suggested_fn
),
applicability,
);
}
}
}
}