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Auto merge of #7805 - aDotInTheVoid:transmute-num-bits, r=camsteffen
Add lint transmute_num_to_bytes Closes #7803 changelog: [`transmute_num_to_bytes`] new lint
2 parents 57dc034 + 5896980 commit b9b11a9

8 files changed

+194
-3
lines changed

‎CHANGELOG.md

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@@ -3025,6 +3025,7 @@ Released 2018-09-13
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[`transmute_int_to_bool`]: https://rust-lang.github.io/rust-clippy/master/index.html#transmute_int_to_bool
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[`transmute_int_to_char`]: https://rust-lang.github.io/rust-clippy/master/index.html#transmute_int_to_char
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[`transmute_int_to_float`]: https://rust-lang.github.io/rust-clippy/master/index.html#transmute_int_to_float
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[`transmute_num_to_bytes`]: https://rust-lang.github.io/rust-clippy/master/index.html#transmute_num_to_bytes
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[`transmute_ptr_to_ptr`]: https://rust-lang.github.io/rust-clippy/master/index.html#transmute_ptr_to_ptr
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[`transmute_ptr_to_ref`]: https://rust-lang.github.io/rust-clippy/master/index.html#transmute_ptr_to_ref
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[`transmutes_expressible_as_ptr_casts`]: https://rust-lang.github.io/rust-clippy/master/index.html#transmutes_expressible_as_ptr_casts

‎clippy_lints/src/lib.register_all.rs

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@@ -267,6 +267,7 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![
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LintId::of(transmute::TRANSMUTE_INT_TO_BOOL),
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LintId::of(transmute::TRANSMUTE_INT_TO_CHAR),
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LintId::of(transmute::TRANSMUTE_INT_TO_FLOAT),
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LintId::of(transmute::TRANSMUTE_NUM_TO_BYTES),
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LintId::of(transmute::TRANSMUTE_PTR_TO_REF),
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LintId::of(transmute::UNSOUND_COLLECTION_TRANSMUTE),
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LintId::of(transmute::WRONG_TRANSMUTE),

‎clippy_lints/src/lib.register_complexity.rs

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@@ -82,6 +82,7 @@ store.register_group(true, "clippy::complexity", Some("clippy_complexity"), vec!
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LintId::of(transmute::TRANSMUTE_INT_TO_BOOL),
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LintId::of(transmute::TRANSMUTE_INT_TO_CHAR),
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LintId::of(transmute::TRANSMUTE_INT_TO_FLOAT),
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LintId::of(transmute::TRANSMUTE_NUM_TO_BYTES),
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LintId::of(transmute::TRANSMUTE_PTR_TO_REF),
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LintId::of(types::BORROWED_BOX),
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LintId::of(types::TYPE_COMPLEXITY),

‎clippy_lints/src/lib.register_lints.rs

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@@ -450,6 +450,7 @@ store.register_lints(&[
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transmute::TRANSMUTE_INT_TO_BOOL,
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transmute::TRANSMUTE_INT_TO_CHAR,
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transmute::TRANSMUTE_INT_TO_FLOAT,
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transmute::TRANSMUTE_NUM_TO_BYTES,
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transmute::TRANSMUTE_PTR_TO_PTR,
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transmute::TRANSMUTE_PTR_TO_REF,
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transmute::UNSOUND_COLLECTION_TRANSMUTE,

‎clippy_lints/src/transmute/mod.rs

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@@ -3,6 +3,7 @@ mod transmute_float_to_int;
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mod transmute_int_to_bool;
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mod transmute_int_to_char;
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mod transmute_int_to_float;
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mod transmute_num_to_bytes;
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mod transmute_ptr_to_ptr;
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mod transmute_ptr_to_ref;
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mod transmute_ref_to_ref;
@@ -261,6 +262,28 @@ declare_clippy_lint! {
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"transmutes from a float to an integer"
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}
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declare_clippy_lint! {
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/// # What it does
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/// Checks for transmutes from a number to an array of `u8`
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///
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/// ### Why this is bad?
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/// Transmutes are dangerous and error-prone, whereas `to_ne_bytes`
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/// is intuitive and safe.
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///
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/// ### Example
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/// ```rust
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/// unsafe {
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/// let x: [u8; 8] = std::mem::transmute(1i64);
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/// }
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///
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/// // should be
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/// let x: [u8; 8] = 0i64.to_ne_bytes();
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/// ```
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pub TRANSMUTE_NUM_TO_BYTES,
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complexity,
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"transmutes from a number to an array of `u8`"
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}
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for transmutes from a pointer to a pointer, or
@@ -330,6 +353,7 @@ declare_lint_pass!(Transmute => [
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TRANSMUTE_INT_TO_BOOL,
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TRANSMUTE_INT_TO_FLOAT,
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TRANSMUTE_FLOAT_TO_INT,
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TRANSMUTE_NUM_TO_BYTES,
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UNSOUND_COLLECTION_TRANSMUTE,
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TRANSMUTES_EXPRESSIBLE_AS_PTR_CASTS,
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]);
@@ -365,6 +389,7 @@ impl<'tcx> LateLintPass<'tcx> for Transmute {
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linted |= transmute_int_to_bool::check(cx, e, from_ty, to_ty, args);
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linted |= transmute_int_to_float::check(cx, e, from_ty, to_ty, args, const_context);
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linted |= transmute_float_to_int::check(cx, e, from_ty, to_ty, args, const_context);
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linted |= transmute_num_to_bytes::check(cx, e, from_ty, to_ty, args, const_context);
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linted |= unsound_collection_transmute::check(cx, e, from_ty, to_ty);
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if !linted {

‎clippy_lints/src/transmute/transmute_num_to_bytes.rs

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@@ -0,0 +1,49 @@
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use super::TRANSMUTE_NUM_TO_BYTES;
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use clippy_utils::diagnostics::span_lint_and_then;
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use clippy_utils::sugg;
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use rustc_errors::Applicability;
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use rustc_hir::Expr;
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use rustc_lint::LateContext;
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use rustc_middle::ty::{self, Ty, UintTy};
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/// Checks for `transmute_int_to_float` lint.
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/// Returns `true` if it's triggered, otherwise returns `false`.
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pub(super) fn check<'tcx>(
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cx: &LateContext<'tcx>,
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e: &'tcx Expr<'_>,
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from_ty: Ty<'tcx>,
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to_ty: Ty<'tcx>,
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args: &'tcx [Expr<'_>],
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const_context: bool,
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) -> bool {
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match (&from_ty.kind(), &to_ty.kind()) {
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(ty::Int(_) | ty::Uint(_) | ty::Float(_), ty::Array(arr_ty, _)) => {
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if !matches!(arr_ty.kind(), ty::Uint(UintTy::U8)) {
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return false;
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}
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if matches!(from_ty.kind(), ty::Float(_)) && const_context {
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// TODO: Remove when const_float_bits_conv is stabilized
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// rust#72447
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return false;
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}
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span_lint_and_then(
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cx,
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TRANSMUTE_NUM_TO_BYTES,
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e.span,
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&format!("transmute from a `{}` to a `{}`", from_ty, to_ty),
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|diag| {
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let arg = sugg::Sugg::hir(cx, &args[0], "..");
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diag.span_suggestion(
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e.span,
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"consider using `to_ne_bytes()`",
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format!("{}.to_ne_bytes()", arg.to_string()),
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Applicability::Unspecified,
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);
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},
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);
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true
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},
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_ => false,
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}
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}

‎tests/ui/transmute.rs

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@@ -103,6 +103,33 @@ mod int_to_float {
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}
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}
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mod num_to_bytes {
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fn test() {
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unsafe {
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let _: [u8; 1] = std::mem::transmute(0u8);
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let _: [u8; 4] = std::mem::transmute(0u32);
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let _: [u8; 16] = std::mem::transmute(0u128);
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let _: [u8; 1] = std::mem::transmute(0i8);
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let _: [u8; 4] = std::mem::transmute(0i32);
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let _: [u8; 16] = std::mem::transmute(0i128);
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let _: [u8; 4] = std::mem::transmute(0.0f32);
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let _: [u8; 8] = std::mem::transmute(0.0f64);
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}
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}
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const fn test_const() {
120+
unsafe {
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let _: [u8; 1] = std::mem::transmute(0u8);
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let _: [u8; 4] = std::mem::transmute(0u32);
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let _: [u8; 16] = std::mem::transmute(0u128);
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let _: [u8; 1] = std::mem::transmute(0i8);
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let _: [u8; 4] = std::mem::transmute(0i32);
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let _: [u8; 16] = std::mem::transmute(0i128);
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let _: [u8; 4] = std::mem::transmute(0.0f32);
128+
let _: [u8; 8] = std::mem::transmute(0.0f64);
129+
}
130+
}
131+
}
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fn bytes_to_str(b: &[u8], mb: &mut [u8]) {
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let _: &str = unsafe { std::mem::transmute(b) };
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let _: &mut str = unsafe { std::mem::transmute(mb) };

‎tests/ui/transmute.stderr

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@@ -140,19 +140,105 @@ error: transmute from a `i64` to a `f64`
140140
LL | let _: f64 = unsafe { std::mem::transmute(0_i64) };
141141
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `f64::from_bits(0_i64 as u64)`
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143+
error: transmute from a `u8` to a `[u8; 1]`
144+
--> $DIR/transmute.rs:109:30
145+
|
146+
LL | let _: [u8; 1] = std::mem::transmute(0u8);
147+
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0u8.to_ne_bytes()`
148+
|
149+
= note: `-D clippy::transmute-num-to-bytes` implied by `-D warnings`
150+
151+
error: transmute from a `u32` to a `[u8; 4]`
152+
--> $DIR/transmute.rs:110:30
153+
|
154+
LL | let _: [u8; 4] = std::mem::transmute(0u32);
155+
| ^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0u32.to_ne_bytes()`
156+
157+
error: transmute from a `u128` to a `[u8; 16]`
158+
--> $DIR/transmute.rs:111:31
159+
|
160+
LL | let _: [u8; 16] = std::mem::transmute(0u128);
161+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0u128.to_ne_bytes()`
162+
163+
error: transmute from a `i8` to a `[u8; 1]`
164+
--> $DIR/transmute.rs:112:30
165+
|
166+
LL | let _: [u8; 1] = std::mem::transmute(0i8);
167+
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0i8.to_ne_bytes()`
168+
169+
error: transmute from a `i32` to a `[u8; 4]`
170+
--> $DIR/transmute.rs:113:30
171+
|
172+
LL | let _: [u8; 4] = std::mem::transmute(0i32);
173+
| ^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0i32.to_ne_bytes()`
174+
175+
error: transmute from a `i128` to a `[u8; 16]`
176+
--> $DIR/transmute.rs:114:31
177+
|
178+
LL | let _: [u8; 16] = std::mem::transmute(0i128);
179+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0i128.to_ne_bytes()`
180+
181+
error: transmute from a `f32` to a `[u8; 4]`
182+
--> $DIR/transmute.rs:115:30
183+
|
184+
LL | let _: [u8; 4] = std::mem::transmute(0.0f32);
185+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0.0f32.to_ne_bytes()`
186+
187+
error: transmute from a `f64` to a `[u8; 8]`
188+
--> $DIR/transmute.rs:116:30
189+
|
190+
LL | let _: [u8; 8] = std::mem::transmute(0.0f64);
191+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0.0f64.to_ne_bytes()`
192+
193+
error: transmute from a `u8` to a `[u8; 1]`
194+
--> $DIR/transmute.rs:121:30
195+
|
196+
LL | let _: [u8; 1] = std::mem::transmute(0u8);
197+
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0u8.to_ne_bytes()`
198+
199+
error: transmute from a `u32` to a `[u8; 4]`
200+
--> $DIR/transmute.rs:122:30
201+
|
202+
LL | let _: [u8; 4] = std::mem::transmute(0u32);
203+
| ^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0u32.to_ne_bytes()`
204+
205+
error: transmute from a `u128` to a `[u8; 16]`
206+
--> $DIR/transmute.rs:123:31
207+
|
208+
LL | let _: [u8; 16] = std::mem::transmute(0u128);
209+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0u128.to_ne_bytes()`
210+
211+
error: transmute from a `i8` to a `[u8; 1]`
212+
--> $DIR/transmute.rs:124:30
213+
|
214+
LL | let _: [u8; 1] = std::mem::transmute(0i8);
215+
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0i8.to_ne_bytes()`
216+
217+
error: transmute from a `i32` to a `[u8; 4]`
218+
--> $DIR/transmute.rs:125:30
219+
|
220+
LL | let _: [u8; 4] = std::mem::transmute(0i32);
221+
| ^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0i32.to_ne_bytes()`
222+
223+
error: transmute from a `i128` to a `[u8; 16]`
224+
--> $DIR/transmute.rs:126:31
225+
|
226+
LL | let _: [u8; 16] = std::mem::transmute(0i128);
227+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0i128.to_ne_bytes()`
228+
143229
error: transmute from a `&[u8]` to a `&str`
144-
--> $DIR/transmute.rs:107:28
230+
--> $DIR/transmute.rs:134:28
145231
|
146232
LL | let _: &str = unsafe { std::mem::transmute(b) };
147233
| ^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `std::str::from_utf8(b).unwrap()`
148234
|
149235
= note: `-D clippy::transmute-bytes-to-str` implied by `-D warnings`
150236

151237
error: transmute from a `&mut [u8]` to a `&mut str`
152-
--> $DIR/transmute.rs:108:32
238+
--> $DIR/transmute.rs:135:32
153239
|
154240
LL | let _: &mut str = unsafe { std::mem::transmute(mb) };
155241
| ^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `std::str::from_utf8_mut(mb).unwrap()`
156242

157-
error: aborting due to 24 previous errors
243+
error: aborting due to 38 previous errors
158244

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