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use clippy_utils::diagnostics::span_lint_and_sugg; | ||
use clippy_utils::match_def_path; | ||
use clippy_utils::source::snippet; | ||
use rustc_errors::Applicability; | ||
use rustc_hir::{ExprKind, QPath, TyKind}; | ||
use rustc_lint::{LateContext, LateLintPass}; | ||
use rustc_session::declare_lint_pass; | ||
use rustc_span::sym; | ||
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||
declare_clippy_lint! { | ||
/// ### What it does | ||
/// Checks for usage of `BufReader::new` with `Stdin` or `StdinLock`. | ||
/// | ||
/// ### Why is this bad? | ||
/// `Stdin` is already buffered. Re-buffering it only increase the memcpy calls. | ||
/// | ||
/// ### Example | ||
/// ```no_run | ||
/// let reader = std::io::BufReader::new(std::io::stdin()); | ||
/// ``` | ||
/// Use instead: | ||
/// ```no_run | ||
/// let stdin = std::io::stdin(); | ||
/// let reader = stdin.lock(); | ||
/// ``` | ||
#[clippy::version = "1.84.0"] | ||
pub BUFREADER_STDIN, | ||
perf, | ||
"using `BufReader::new` with `Stdin` or `StdinLock` is unnecessary and less efficient" | ||
} | ||
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declare_lint_pass!(BufreaderStdinlock => [BUFREADER_STDIN]); | ||
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impl<'tcx> LateLintPass<'tcx> for BufreaderStdinlock { | ||
fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &rustc_hir::Expr<'tcx>) { | ||
if e.span.from_expansion() { | ||
return; | ||
} | ||
if let ExprKind::Call(func, [arg]) = e.kind | ||
&& let ExprKind::Path(QPath::TypeRelative(ty, seg)) = func.kind | ||
&& seg.ident.name == sym::new | ||
&& let TyKind::Path(ref qpath) = ty.kind | ||
&& let Some(did) = cx.qpath_res(qpath, ty.hir_id).opt_def_id() | ||
&& match_def_path(cx, did, &["std", "io", "buffered", "bufreader", "BufReader"]) | ||
&& let arg_ty = cx.typeck_results().expr_ty(arg) | ||
&& let Some(arg_did) = arg_ty.ty_adt_def().map(|def| def.did()) | ||
{ | ||
if match_def_path(cx, arg_did, &["std", "io", "stdio", "Stdin"]) { | ||
span_lint_and_sugg( | ||
cx, | ||
&BUFREADER_STDIN, | ||
e.span, | ||
"using `BufReader::new` with `Stdin`", | ||
"instead of wrapping `Stdin` in `BufReader`, use the `lock` method directly", | ||
format!("{}.lock()", snippet(cx, arg.span, "..")), | ||
Applicability::MachineApplicable, | ||
); | ||
} else if match_def_path(cx, arg_did, &["std", "io", "stdio", "StdinLock"]) { | ||
span_lint_and_sugg( | ||
cx, | ||
&BUFREADER_STDIN, | ||
e.span, | ||
"using `BufReader::new` with `Stdin`", | ||
"instead of wrapping `StdinLock` in `BufReader`, use it self", | ||
snippet(cx, arg.span, "..").to_string(), | ||
Applicability::MachineApplicable, | ||
); | ||
} else { | ||
return; | ||
}; | ||
} | ||
} | ||
} |
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Original file line number | Diff line number | Diff line change |
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#![warn(clippy::bufreader_stdin)] | ||
use std::io::{self, BufReader}; | ||
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fn main() { | ||
let a = io::stdin(); | ||
let reader = a.lock(); | ||
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let b = io::stdin().lock(); | ||
let reader = b; | ||
} |
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,10 @@ | ||
#![warn(clippy::BUFREADER_STDIN)] | ||
use std::io::{self, BufReader}; | ||
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fn main() { | ||
let a = io::stdin(); | ||
let reader = BufReader::new(a); | ||
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let b = io::stdin().lock(); | ||
let reader = BufReader::new(b); | ||
} |
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Original file line number | Diff line number | Diff line change |
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error: unknown lint: `clippy::BUFREADER_STDIN` | ||
--> tests/ui/bufreader_stdin.rs:1:9 | ||
| | ||
LL | #![warn(clippy::BUFREADER_STDIN)] | ||
| ^^^^^^^^^^^^^^^^^^^^^^^ help: did you mean: `clippy::bufreader_stdin` | ||
| | ||
= note: `-D unknown-lints` implied by `-D warnings` | ||
= help: to override `-D warnings` add `#[allow(unknown_lints)]` | ||
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error: using `BufReader::new` with `Stdin` | ||
--> tests/ui/bufreader_stdin.rs:6:18 | ||
| | ||
LL | let reader = BufReader::new(a); | ||
| ^^^^^^^^^^^^^^^^^ | ||
| | ||
= note: `-D clippy::bufreader-stdin` implied by `-D warnings` | ||
= help: to override `-D warnings` add `#[allow(clippy::bufreader_stdin)]` | ||
help: instead of wrapping `Stdin` in `BufReader`, use the `lock` method directly | ||
| | ||
LL | let reader = a.lock(); | ||
| ~~~~~~~~ | ||
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error: using `BufReader::new` with `Stdin` | ||
--> tests/ui/bufreader_stdin.rs:9:18 | ||
| | ||
LL | let reader = BufReader::new(b); | ||
| ^^^^^^^^^^^^^^^^^ help: instead of wrapping `StdinLock` in `BufReader`, use it self: `b` | ||
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error: aborting due to 3 previous errors | ||
|