rust-clippy/clippy_lints/src/duration_subsec.rs

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// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use if_chain::if_chain;
use rustc::hir::*;
use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
use rustc::{declare_tool_lint, lint_array};
use rustc_errors::Applicability;
use syntax::source_map::Spanned;
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use crate::consts::{constant, Constant};
use crate::utils::paths;
use crate::utils::{match_type, snippet_with_applicability, span_lint_and_sugg, walk_ptrs_ty};
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/// **What it does:** Checks for calculation of subsecond microseconds or milliseconds
/// from other `Duration` methods.
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///
/// **Why is this bad?** It's more concise to call `Duration::subsec_micros()` or
/// `Duration::subsec_millis()` than to calculate them.
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///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// let dur = Duration::new(5, 0);
/// let _micros = dur.subsec_nanos() / 1_000;
/// let _millis = dur.subsec_nanos() / 1_000_000;
/// ```
declare_clippy_lint! {
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pub DURATION_SUBSEC,
complexity,
"checks for calculation of subsecond microseconds or milliseconds"
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}
#[derive(Copy, Clone)]
pub struct DurationSubsec;
impl LintPass for DurationSubsec {
fn get_lints(&self) -> LintArray {
lint_array!(DURATION_SUBSEC)
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for DurationSubsec {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
if_chain! {
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if let ExprKind::Binary(Spanned { node: BinOpKind::Div, .. }, ref left, ref right) = expr.node;
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if let ExprKind::MethodCall(ref method_path, _ , ref args) = left.node;
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if match_type(cx, walk_ptrs_ty(cx.tables.expr_ty(&args[0])), &paths::DURATION);
if let Some((Constant::Int(divisor), _)) = constant(cx, cx.tables, right);
then {
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let suggested_fn = match (method_path.ident.as_str().as_ref(), divisor) {
("subsec_micros", 1_000) | ("subsec_nanos", 1_000_000) => "subsec_millis",
("subsec_nanos", 1_000) => "subsec_micros",
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_ => return,
};
let mut applicability = Applicability::MachineApplicable;
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span_lint_and_sugg(
cx,
DURATION_SUBSEC,
expr.span,
&format!("Calling `{}()` is more concise than this calculation", suggested_fn),
"try",
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format!(
"{}.{}()",
snippet_with_applicability(cx, args[0].span, "_", &mut applicability),
suggested_fn
),
applicability,
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);
}
}
}
}