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changelog: Add manual_as_slice lint
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‎CHANGELOG.md‎

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@@ -5944,6 +5944,7 @@ Released 2018-09-13
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[`macro_use_imports`]: https://rust-lang.github.io/rust-clippy/master/index.html#macro_use_imports
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[`main_recursion`]: https://rust-lang.github.io/rust-clippy/master/index.html#main_recursion
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[`manual_abs_diff`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_abs_diff
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[`manual_as_slice`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_as_slice
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[`manual_assert`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_assert
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[`manual_async_fn`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_async_fn
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[`manual_bits`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_bits

‎clippy_lints/src/declared_lints.rs‎

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@@ -290,6 +290,7 @@ pub static LINTS: &[&crate::LintInfo] = &[
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crate::macro_use::MACRO_USE_IMPORTS_INFO,
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crate::main_recursion::MAIN_RECURSION_INFO,
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crate::manual_abs_diff::MANUAL_ABS_DIFF_INFO,
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crate::manual_as_slice::MANUAL_AS_SLICE_INFO,
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crate::manual_assert::MANUAL_ASSERT_INFO,
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crate::manual_async_fn::MANUAL_ASYNC_FN_INFO,
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crate::manual_bits::MANUAL_BITS_INFO,

‎clippy_lints/src/lib.rs‎

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@@ -205,6 +205,7 @@ mod macro_metavars_in_unsafe;
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mod macro_use;
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mod main_recursion;
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mod manual_abs_diff;
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mod manual_as_slice;
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mod manual_assert;
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mod manual_async_fn;
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mod manual_bits;
@@ -948,5 +949,6 @@ pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
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store.register_late_pass(move |_| Box::new(redundant_test_prefix::RedundantTestPrefix));
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store.register_late_pass(|_| Box::new(cloned_ref_to_slice_refs::ClonedRefToSliceRefs::new(conf)));
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store.register_late_pass(|_| Box::new(infallible_try_from::InfallibleTryFrom));
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store.register_late_pass(|_| Box::new(manual_as_slice::ManualAsSlice));
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// add lints here, do not remove this comment, it's used in `new_lint`
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}

‎clippy_lints/src/manual_as_slice.rs‎

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use clippy_utils::diagnostics::span_lint_and_then;
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use rustc_errors::Applicability;
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use rustc_hir::{Expr, ExprKind, LangItem, Mutability, QPath};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::ty::TyKind;
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use rustc_session::declare_lint_pass;
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use rustc_span::symbol::sym;
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declare_clippy_lint! {
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/// ### What it does
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///
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/// Detects if a full range slice reference is used instead of using the `.as_slice()` method.
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///
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/// ### Why is this bad?
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///
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/// Using the `some_value.as_slice()` method is more explicit then using `&some_value[..]`
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///
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/// ### Example
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/// ```no_run
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/// let array: [u8; 4] = [0; 4];
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/// let slice = &array[..];
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/// ```
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/// Use instead:
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/// ```no_run
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/// let array: [u8; 4] = [0; 4];
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/// let slice = array.as_slice();
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/// ```
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#[clippy::version = "1.88.0"]
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pub MANUAL_AS_SLICE,
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nursery,
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"Use as slice instead of borrow full range."
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}
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declare_lint_pass!(ManualAsSlice => [MANUAL_AS_SLICE]);
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impl LateLintPass<'_> for ManualAsSlice {
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fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
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if let ExprKind::AddrOf(_, mutability, borrow) = expr.kind
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&& let ExprKind::Index(value, index, index_span) = borrow.kind
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&& let ExprKind::Struct(qpath, _, _) = index.kind
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&& let QPath::LangItem(LangItem::RangeFull, _) = qpath
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{
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let sugg_tail = match mutability {
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Mutability::Not => ".as_slice()",
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Mutability::Mut => ".as_mut_slice()",
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};
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let borrow_span = expr.span.until(borrow.span);
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let app = Applicability::MachineApplicable;
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match cx.typeck_results().expr_ty(value).kind() {
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TyKind::Array(_, _) | TyKind::Slice(_) => {},
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TyKind::Ref(_, t, _) if let TyKind::Array(_, _) | TyKind::Slice(_) = t.kind() => {},
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TyKind::Adt(adt, _) if cx.tcx.is_diagnostic_item(sym::Vec, adt.did()) => {},
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_ => return,
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}
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span_lint_and_then(cx, MANUAL_AS_SLICE, expr.span, "using a full range slice", |diag| {
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diag.multipart_suggestion(
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"try",
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vec![(borrow_span, String::new()), (index_span, sugg_tail.to_string())],
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app,
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);
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});
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}
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}
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}

‎tests/ui/manual_as_slice.fixed‎

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#![feature(new_range_api)]
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#![allow(clippy::redundant_slicing)]
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#![warn(clippy::manual_as_slice)]
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mod nested_1 {
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pub(crate) mod nested_2 {
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pub(crate) const SOME_VALUE: [u8; 4] = [1, 2, 3, 4];
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}
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}
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fn main() {
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let array: [u8; 4] = [0; 4];
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let slice: &[u8] = array.as_slice();
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//~^ manual_as_slice
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let mut array: [u8; 4] = [0; 4];
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let mut slice: &[u8] = array.as_mut_slice();
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//~^ manual_as_slice
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let slice: &[u8] = nested_1::nested_2::SOME_VALUE.as_slice();
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//~^ manual_as_slice
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let slice = b"foo";
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let slice: &[u8] = slice.as_slice();
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//~^ manual_as_slice
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let slice = &[1, 2, 3, 4];
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let slice: &[u8] = slice.as_slice();
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//~^ manual_as_slice
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macro_rules! perform_the_slice {
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($a:expr) => {
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$a.as_slice()
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//~^ manual_as_slice
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};
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}
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perform_the_slice!([1, 2, 3]);
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let slice: &[u8] = vec![1, 2, 3].as_slice();
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//~^ manual_as_slice
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let slice = &"foo"[..];
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struct Count;
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impl<R: std::range::RangeBounds<()>> std::ops::Index<R> for Count {
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type Output = ();
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fn index(&self, _: R) -> &Self::Output {
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&()
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}
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}
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let count = &Count[..];
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}

‎tests/ui/manual_as_slice.rs‎

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#![feature(new_range_api)]
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#![allow(clippy::redundant_slicing)]
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#![warn(clippy::manual_as_slice)]
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mod nested_1 {
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pub(crate) mod nested_2 {
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pub(crate) const SOME_VALUE: [u8; 4] = [1, 2, 3, 4];
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}
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}
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fn main() {
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let array: [u8; 4] = [0; 4];
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let slice: &[u8] = &array[..];
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//~^ manual_as_slice
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let mut array: [u8; 4] = [0; 4];
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let mut slice: &[u8] = &mut array[..];
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//~^ manual_as_slice
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let slice: &[u8] = &nested_1::nested_2::SOME_VALUE[..];
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//~^ manual_as_slice
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let slice = b"foo";
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let slice: &[u8] = &slice[..];
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//~^ manual_as_slice
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let slice = &[1, 2, 3, 4];
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let slice: &[u8] = &slice[..];
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//~^ manual_as_slice
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macro_rules! perform_the_slice {
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($a:expr) => {
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&$a[..]
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//~^ manual_as_slice
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};
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}
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perform_the_slice!([1, 2, 3]);
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let slice: &[u8] = &vec![1, 2, 3][..];
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//~^ manual_as_slice
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let slice = &"foo"[..];
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struct Count;
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impl<R: std::range::RangeBounds<()>> std::ops::Index<R> for Count {
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type Output = ();
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fn index(&self, _: R) -> &Self::Output {
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&()
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}
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}
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let count = &Count[..];
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}

‎tests/ui/manual_as_slice.stderr‎

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error: using a full range slice
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--> tests/ui/manual_as_slice.rs:13:24
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|
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LL | let slice: &[u8] = &array[..];
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| ^^^^^^^^^^
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|
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= note: `-D clippy::manual-as-slice` implied by `-D warnings`
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= help: to override `-D warnings` add `#[allow(clippy::manual_as_slice)]`
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help: try
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|
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LL - let slice: &[u8] = &array[..];
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LL + let slice: &[u8] = array.as_slice();
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|
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error: using a full range slice
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--> tests/ui/manual_as_slice.rs:17:28
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|
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LL | let mut slice: &[u8] = &mut array[..];
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| ^^^^^^^^^^^^^^
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|
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help: try
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|
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LL - let mut slice: &[u8] = &mut array[..];
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LL + let mut slice: &[u8] = array.as_mut_slice();
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|
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error: using a full range slice
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--> tests/ui/manual_as_slice.rs:20:24
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|
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LL | let slice: &[u8] = &nested_1::nested_2::SOME_VALUE[..];
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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|
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help: try
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|
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LL - let slice: &[u8] = &nested_1::nested_2::SOME_VALUE[..];
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LL + let slice: &[u8] = nested_1::nested_2::SOME_VALUE.as_slice();
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|
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error: using a full range slice
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--> tests/ui/manual_as_slice.rs:24:24
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|
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LL | let slice: &[u8] = &slice[..];
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| ^^^^^^^^^^
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|
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help: try
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|
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LL - let slice: &[u8] = &slice[..];
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LL + let slice: &[u8] = slice.as_slice();
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|
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error: using a full range slice
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--> tests/ui/manual_as_slice.rs:28:24
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|
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LL | let slice: &[u8] = &slice[..];
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| ^^^^^^^^^^
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|
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help: try
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|
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LL - let slice: &[u8] = &slice[..];
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LL + let slice: &[u8] = slice.as_slice();
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|
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error: using a full range slice
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--> tests/ui/manual_as_slice.rs:33:13
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|
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LL | &$a[..]
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| ^^^^^^^
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...
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LL | perform_the_slice!([1, 2, 3]);
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| ----------------------------- in this macro invocation
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|
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= note: this error originates in the macro `perform_the_slice` (in Nightly builds, run with -Z macro-backtrace for more info)
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help: try
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|
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LL - &$a[..]
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LL + $a.as_slice()
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|
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error: using a full range slice
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--> tests/ui/manual_as_slice.rs:40:24
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|
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LL | let slice: &[u8] = &vec![1, 2, 3][..];
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| ^^^^^^^^^^^^^^^^^^
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|
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help: try
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|
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LL - let slice: &[u8] = &vec![1, 2, 3][..];
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LL + let slice: &[u8] = vec![1, 2, 3].as_slice();
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|
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error: aborting due to 7 previous errors
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