Rollup merge of #136083 - bend-n:⃤⃤, r=lcnr

Suggest {to,from}_ne_bytes for transmutations between arrays and integers, etc

implements #136067

Rust has helper methods for many kinds of safe transmutes, for example integer<->bytes. This is a lint against using transmute for these cases.

```rs
fn bytes_at_home(x: [u8; 4]) -> u32 {
   transmute(x)
}

// other examples
transmute::<[u8; 2], u16>();
transmute::<[u8; 8], f64>();
transmute::<u32, [u8; 4]>();
transmute::<char, u32>();
transmute::<u32, char>();
```
It would be handy to suggest `u32::from_ne_bytes(x)`.
This is implemented for `[u8; _]` -> `{float int}`

This also implements the cases:
`fXX` <-> `uXX` = `{from_bits, to_bits}`
`uXX` -> `iXX` via `cast_unsigned` and `cast_signed`
{`char` -> `u32`, `bool` -> `n8`} via `from`
`u32` -> `char` via `from_u32_unchecked` (note: notes `from_u32().unwrap()`) (contested)
`u8` -> `bool` via `==` (debatable)

---
try-job: aarch64-gnu
try-job: test-various

20 files changed, 87 insertions, 67 deletions

diff --git a/src/tools/clippy/tests/ui/blocks_in_conditions.fixed b/src/tools/clippy/tests/ui/blocks_in_conditions.fixed
index c82276b358e..e696896538e 100644
--- a/src/tools/clippy/tests/ui/blocks_in_conditions.fixed
+++ b/src/tools/clippy/tests/ui/blocks_in_conditions.fixed
@@ -1,7 +1,13 @@
 //@aux-build:proc_macro_attr.rs
 
 #![warn(clippy::blocks_in_conditions)]
-#![allow(unused, clippy::needless_if, clippy::missing_transmute_annotations)]
+#![allow(
+    unused,
+    unnecessary_transmutes,
+    clippy::let_and_return,
+    clippy::needless_if,
+    clippy::missing_transmute_annotations
+)]
 #![warn(clippy::nonminimal_bool)]
 
 macro_rules! blocky {
diff --git a/src/tools/clippy/tests/ui/blocks_in_conditions.rs b/src/tools/clippy/tests/ui/blocks_in_conditions.rs
index 6a4a7c62106..8c8f3249b8a 100644
--- a/src/tools/clippy/tests/ui/blocks_in_conditions.rs
+++ b/src/tools/clippy/tests/ui/blocks_in_conditions.rs
@@ -1,7 +1,13 @@
 //@aux-build:proc_macro_attr.rs
 
 #![warn(clippy::blocks_in_conditions)]
-#![allow(unused, clippy::needless_if, clippy::missing_transmute_annotations)]
+#![allow(
+    unused,
+    unnecessary_transmutes,
+    clippy::let_and_return,
+    clippy::needless_if,
+    clippy::missing_transmute_annotations
+)]
 #![warn(clippy::nonminimal_bool)]
 
 macro_rules! blocky {
diff --git a/src/tools/clippy/tests/ui/blocks_in_conditions.stderr b/src/tools/clippy/tests/ui/blocks_in_conditions.stderr
index e57eca5dcee..41ff59c683e 100644
--- a/src/tools/clippy/tests/ui/blocks_in_conditions.stderr
+++ b/src/tools/clippy/tests/ui/blocks_in_conditions.stderr
@@ -1,5 +1,5 @@
 error: in an `if` condition, avoid complex blocks or closures with blocks; instead, move the block or closure higher and bind it with a `let`
-  --> tests/ui/blocks_in_conditions.rs:25:5
+  --> tests/ui/blocks_in_conditions.rs:31:5
    |
 LL | /     if {
 LL | |
@@ -20,13 +20,13 @@ LL ~     }; if res {
    |
 
 error: omit braces around single expression condition
-  --> tests/ui/blocks_in_conditions.rs:37:8
+  --> tests/ui/blocks_in_conditions.rs:43:8
    |
 LL |     if { true } { 6 } else { 10 }
    |        ^^^^^^^^ help: try: `true`
 
 error: this boolean expression can be simplified
-  --> tests/ui/blocks_in_conditions.rs:43:8
+  --> tests/ui/blocks_in_conditions.rs:49:8
    |
 LL |     if true && x == 3 { 6 } else { 10 }
    |        ^^^^^^^^^^^^^^ help: try: `x == 3`
diff --git a/src/tools/clippy/tests/ui/crashes/ice-1782.rs b/src/tools/clippy/tests/ui/crashes/ice-1782.rs
index 4a1886c08af..776b0a93bf7 100644
--- a/src/tools/clippy/tests/ui/crashes/ice-1782.rs
+++ b/src/tools/clippy/tests/ui/crashes/ice-1782.rs
@@ -1,6 +1,6 @@
 //@ check-pass
 
-#![allow(dead_code, unused_variables, invalid_null_arguments)]
+#![allow(dead_code, unused_variables, invalid_null_arguments, unnecessary_transmutes)]
 #![allow(clippy::unnecessary_cast, clippy::missing_transmute_annotations)]
 
 /// Should not trigger an ICE in `SpanlessEq` / `consts::constant`
diff --git a/src/tools/clippy/tests/ui/transmute.rs b/src/tools/clippy/tests/ui/transmute.rs
index 8c8674ac356..2b8b6c539ad 100644
--- a/src/tools/clippy/tests/ui/transmute.rs
+++ b/src/tools/clippy/tests/ui/transmute.rs
@@ -3,6 +3,7 @@
 #![allow(
     dead_code,
     clippy::borrow_as_ptr,
+    unnecessary_transmutes,
     clippy::needless_lifetimes,
     clippy::missing_transmute_annotations
 )]
diff --git a/src/tools/clippy/tests/ui/transmute.stderr b/src/tools/clippy/tests/ui/transmute.stderr
index 4219e09d2ab..1bb70151965 100644
--- a/src/tools/clippy/tests/ui/transmute.stderr
+++ b/src/tools/clippy/tests/ui/transmute.stderr
@@ -1,5 +1,5 @@
 error: transmute from a reference to a pointer
-  --> tests/ui/transmute.rs:32:27
+  --> tests/ui/transmute.rs:33:27
    |
 LL |         let _: *const T = core::mem::transmute(t);
    |                           ^^^^^^^^^^^^^^^^^^^^^^^ help: try: `t as *const T`
@@ -8,61 +8,61 @@ LL |         let _: *const T = core::mem::transmute(t);
    = help: to override `-D warnings` add `#[allow(clippy::useless_transmute)]`
 
 error: transmute from a reference to a pointer
-  --> tests/ui/transmute.rs:35:25
+  --> tests/ui/transmute.rs:36:25
    |
 LL |         let _: *mut T = core::mem::transmute(t);
    |                         ^^^^^^^^^^^^^^^^^^^^^^^ help: try: `t as *const T as *mut T`
 
 error: transmute from a reference to a pointer
-  --> tests/ui/transmute.rs:38:27
+  --> tests/ui/transmute.rs:39:27
    |
 LL |         let _: *const U = core::mem::transmute(t);
    |                           ^^^^^^^^^^^^^^^^^^^^^^^ help: try: `t as *const T as *const U`
 
 error: transmute from a type (`std::vec::Vec<i32>`) to itself
-  --> tests/ui/transmute.rs:46:27
+  --> tests/ui/transmute.rs:47:27
    |
 LL |         let _: Vec<i32> = core::mem::transmute(my_vec());
    |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: transmute from a type (`std::vec::Vec<i32>`) to itself
-  --> tests/ui/transmute.rs:49:27
+  --> tests/ui/transmute.rs:50:27
    |
 LL |         let _: Vec<i32> = core::mem::transmute(my_vec());
    |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: transmute from a type (`std::vec::Vec<i32>`) to itself
-  --> tests/ui/transmute.rs:52:27
+  --> tests/ui/transmute.rs:53:27
    |
 LL |         let _: Vec<i32> = std::mem::transmute(my_vec());
    |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: transmute from a type (`std::vec::Vec<i32>`) to itself
-  --> tests/ui/transmute.rs:55:27
+  --> tests/ui/transmute.rs:56:27
    |
 LL |         let _: Vec<i32> = std::mem::transmute(my_vec());
    |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: transmute from a type (`std::vec::Vec<i32>`) to itself
-  --> tests/ui/transmute.rs:58:27
+  --> tests/ui/transmute.rs:59:27
    |
 LL |         let _: Vec<i32> = my_transmute(my_vec());
    |                           ^^^^^^^^^^^^^^^^^^^^^^
 
 error: transmute from an integer to a pointer
-  --> tests/ui/transmute.rs:61:31
+  --> tests/ui/transmute.rs:62:31
    |
 LL |         let _: *const usize = std::mem::transmute(5_isize);
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `5_isize as *const usize`
 
 error: transmute from an integer to a pointer
-  --> tests/ui/transmute.rs:66:31
+  --> tests/ui/transmute.rs:67:31
    |
 LL |         let _: *const usize = std::mem::transmute(1 + 1usize);
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `(1 + 1usize) as *const usize`
 
 error: transmute from a type (`*const Usize`) to the type that it points to (`Usize`)
-  --> tests/ui/transmute.rs:98:24
+  --> tests/ui/transmute.rs:99:24
    |
 LL |         let _: Usize = core::mem::transmute(int_const_ptr);
    |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -71,25 +71,25 @@ LL |         let _: Usize = core::mem::transmute(int_const_ptr);
    = help: to override `-D warnings` add `#[allow(clippy::crosspointer_transmute)]`
 
 error: transmute from a type (`*mut Usize`) to the type that it points to (`Usize`)
-  --> tests/ui/transmute.rs:101:24
+  --> tests/ui/transmute.rs:102:24
    |
 LL |         let _: Usize = core::mem::transmute(int_mut_ptr);
    |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: transmute from a type (`Usize`) to a pointer to that type (`*const Usize`)
-  --> tests/ui/transmute.rs:104:31
+  --> tests/ui/transmute.rs:105:31
    |
 LL |         let _: *const Usize = core::mem::transmute(my_int());
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: transmute from a type (`Usize`) to a pointer to that type (`*mut Usize`)
-  --> tests/ui/transmute.rs:107:29
+  --> tests/ui/transmute.rs:108:29
    |
 LL |         let _: *mut Usize = core::mem::transmute(my_int());
    |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: transmute from a `u8` to a `bool`
-  --> tests/ui/transmute.rs:114:28
+  --> tests/ui/transmute.rs:115:28
    |
 LL |     let _: bool = unsafe { std::mem::transmute(0_u8) };
    |                            ^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `0_u8 != 0`
@@ -98,7 +98,7 @@ LL |     let _: bool = unsafe { std::mem::transmute(0_u8) };
    = help: to override `-D warnings` add `#[allow(clippy::transmute_int_to_bool)]`
 
 error: transmute from a `u16` to a `f16`
-  --> tests/ui/transmute.rs:121:31
+  --> tests/ui/transmute.rs:122:31
    |
 LL |         let _: f16 = unsafe { std::mem::transmute(0_u16) };
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `f16::from_bits(0_u16)`
@@ -107,97 +107,97 @@ LL |         let _: f16 = unsafe { std::mem::transmute(0_u16) };
    = help: to override `-D warnings` add `#[allow(clippy::transmute_int_to_float)]`
 
 error: transmute from a `i16` to a `f16`
-  --> tests/ui/transmute.rs:124:31
+  --> tests/ui/transmute.rs:125:31
    |
 LL |         let _: f16 = unsafe { std::mem::transmute(0_i16) };
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `f16::from_bits(0_i16 as u16)`
 
 error: transmute from a `u32` to a `f32`
-  --> tests/ui/transmute.rs:127:31
+  --> tests/ui/transmute.rs:128:31
    |
 LL |         let _: f32 = unsafe { std::mem::transmute(0_u32) };
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `f32::from_bits(0_u32)`
 
 error: transmute from a `i32` to a `f32`
-  --> tests/ui/transmute.rs:130:31
+  --> tests/ui/transmute.rs:131:31
    |
 LL |         let _: f32 = unsafe { std::mem::transmute(0_i32) };
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `f32::from_bits(0_i32 as u32)`
 
 error: transmute from a `u64` to a `f64`
-  --> tests/ui/transmute.rs:133:31
+  --> tests/ui/transmute.rs:134:31
    |
 LL |         let _: f64 = unsafe { std::mem::transmute(0_u64) };
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `f64::from_bits(0_u64)`
 
 error: transmute from a `i64` to a `f64`
-  --> tests/ui/transmute.rs:136:31
+  --> tests/ui/transmute.rs:137:31
    |
 LL |         let _: f64 = unsafe { std::mem::transmute(0_i64) };
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `f64::from_bits(0_i64 as u64)`
 
 error: transmute from a `u128` to a `f128`
-  --> tests/ui/transmute.rs:139:32
+  --> tests/ui/transmute.rs:140:32
    |
 LL |         let _: f128 = unsafe { std::mem::transmute(0_u128) };
    |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `f128::from_bits(0_u128)`
 
 error: transmute from a `i128` to a `f128`
-  --> tests/ui/transmute.rs:142:32
+  --> tests/ui/transmute.rs:143:32
    |
 LL |         let _: f128 = unsafe { std::mem::transmute(0_i128) };
    |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `f128::from_bits(0_i128 as u128)`
 
 error: transmute from a `u16` to a `f16`
-  --> tests/ui/transmute.rs:147:39
+  --> tests/ui/transmute.rs:148:39
    |
 LL |         const VALUE16: f16 = unsafe { std::mem::transmute(0_u16) };
    |                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `f16::from_bits(0_u16)`
 
 error: transmute from a `u32` to a `f32`
-  --> tests/ui/transmute.rs:150:39
+  --> tests/ui/transmute.rs:151:39
    |
 LL |         const VALUE32: f32 = unsafe { std::mem::transmute(0_u32) };
    |                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `f32::from_bits(0_u32)`
 
 error: transmute from a `i64` to a `f64`
-  --> tests/ui/transmute.rs:153:39
+  --> tests/ui/transmute.rs:154:39
    |
 LL |         const VALUE64: f64 = unsafe { std::mem::transmute(0_i64) };
    |                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `f64::from_bits(0_i64 as u64)`
 
 error: transmute from a `i128` to a `f128`
-  --> tests/ui/transmute.rs:156:41
+  --> tests/ui/transmute.rs:157:41
    |
 LL |         const VALUE128: f128 = unsafe { std::mem::transmute(0_i128) };
    |                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `f128::from_bits(0_i128 as u128)`
 
 error: transmute from a `i16` to a `f16`
-  --> tests/ui/transmute.rs:160:22
+  --> tests/ui/transmute.rs:161:22
    |
 LL |             unsafe { std::mem::transmute(v) }
    |                      ^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `f16::from_bits(v as u16)`
 
 error: transmute from a `i32` to a `f32`
-  --> tests/ui/transmute.rs:165:22
+  --> tests/ui/transmute.rs:166:22
    |
 LL |             unsafe { std::mem::transmute(v) }
    |                      ^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `f32::from_bits(v as u32)`
 
 error: transmute from a `u64` to a `f64`
-  --> tests/ui/transmute.rs:170:22
+  --> tests/ui/transmute.rs:171:22
    |
 LL |             unsafe { std::mem::transmute(v) }
    |                      ^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `f64::from_bits(v)`
 
 error: transmute from a `u128` to a `f128`
-  --> tests/ui/transmute.rs:175:22
+  --> tests/ui/transmute.rs:176:22
    |
 LL |             unsafe { std::mem::transmute(v) }
    |                      ^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `f128::from_bits(v)`
 
 error: transmute from a `u8` to a `[u8; 1]`
-  --> tests/ui/transmute.rs:184:30
+  --> tests/ui/transmute.rs:185:30
    |
 LL |             let _: [u8; 1] = std::mem::transmute(0u8);
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0u8.to_ne_bytes()`
@@ -206,121 +206,121 @@ LL |             let _: [u8; 1] = std::mem::transmute(0u8);
    = help: to override `-D warnings` add `#[allow(clippy::transmute_num_to_bytes)]`
 
 error: transmute from a `u32` to a `[u8; 4]`
-  --> tests/ui/transmute.rs:187:30
+  --> tests/ui/transmute.rs:188:30
    |
 LL |             let _: [u8; 4] = std::mem::transmute(0u32);
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0u32.to_ne_bytes()`
 
 error: transmute from a `u128` to a `[u8; 16]`
-  --> tests/ui/transmute.rs:190:31
+  --> tests/ui/transmute.rs:191:31
    |
 LL |             let _: [u8; 16] = std::mem::transmute(0u128);
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0u128.to_ne_bytes()`
 
 error: transmute from a `i8` to a `[u8; 1]`
-  --> tests/ui/transmute.rs:193:30
+  --> tests/ui/transmute.rs:194:30
    |
 LL |             let _: [u8; 1] = std::mem::transmute(0i8);
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0i8.to_ne_bytes()`
 
 error: transmute from a `i32` to a `[u8; 4]`
-  --> tests/ui/transmute.rs:196:30
+  --> tests/ui/transmute.rs:197:30
    |
 LL |             let _: [u8; 4] = std::mem::transmute(0i32);
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0i32.to_ne_bytes()`
 
 error: transmute from a `i128` to a `[u8; 16]`
-  --> tests/ui/transmute.rs:199:31
+  --> tests/ui/transmute.rs:200:31
    |
 LL |             let _: [u8; 16] = std::mem::transmute(0i128);
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0i128.to_ne_bytes()`
 
 error: transmute from a `f16` to a `[u8; 2]`
-  --> tests/ui/transmute.rs:202:30
+  --> tests/ui/transmute.rs:203:30
    |
 LL |             let _: [u8; 2] = std::mem::transmute(0.0f16);
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0.0f16.to_ne_bytes()`
 
 error: transmute from a `f32` to a `[u8; 4]`
-  --> tests/ui/transmute.rs:205:30
+  --> tests/ui/transmute.rs:206:30
    |
 LL |             let _: [u8; 4] = std::mem::transmute(0.0f32);
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0.0f32.to_ne_bytes()`
 
 error: transmute from a `f64` to a `[u8; 8]`
-  --> tests/ui/transmute.rs:208:30
+  --> tests/ui/transmute.rs:209:30
    |
 LL |             let _: [u8; 8] = std::mem::transmute(0.0f64);
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0.0f64.to_ne_bytes()`
 
 error: transmute from a `f128` to a `[u8; 16]`
-  --> tests/ui/transmute.rs:211:31
+  --> tests/ui/transmute.rs:212:31
    |
 LL |             let _: [u8; 16] = std::mem::transmute(0.0f128);
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0.0f128.to_ne_bytes()`
 
 error: transmute from a `u8` to a `[u8; 1]`
-  --> tests/ui/transmute.rs:217:30
+  --> tests/ui/transmute.rs:218:30
    |
 LL |             let _: [u8; 1] = std::mem::transmute(0u8);
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0u8.to_ne_bytes()`
 
 error: transmute from a `u32` to a `[u8; 4]`
-  --> tests/ui/transmute.rs:220:30
+  --> tests/ui/transmute.rs:221:30
    |
 LL |             let _: [u8; 4] = std::mem::transmute(0u32);
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0u32.to_ne_bytes()`
 
 error: transmute from a `u128` to a `[u8; 16]`
-  --> tests/ui/transmute.rs:223:31
+  --> tests/ui/transmute.rs:224:31
    |
 LL |             let _: [u8; 16] = std::mem::transmute(0u128);
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0u128.to_ne_bytes()`
 
 error: transmute from a `i8` to a `[u8; 1]`
-  --> tests/ui/transmute.rs:226:30
+  --> tests/ui/transmute.rs:227:30
    |
 LL |             let _: [u8; 1] = std::mem::transmute(0i8);
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0i8.to_ne_bytes()`
 
 error: transmute from a `i32` to a `[u8; 4]`
-  --> tests/ui/transmute.rs:229:30
+  --> tests/ui/transmute.rs:230:30
    |
 LL |             let _: [u8; 4] = std::mem::transmute(0i32);
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0i32.to_ne_bytes()`
 
 error: transmute from a `i128` to a `[u8; 16]`
-  --> tests/ui/transmute.rs:232:31
+  --> tests/ui/transmute.rs:233:31
    |
 LL |             let _: [u8; 16] = std::mem::transmute(0i128);
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0i128.to_ne_bytes()`
 
 error: transmute from a `f16` to a `[u8; 2]`
-  --> tests/ui/transmute.rs:235:30
+  --> tests/ui/transmute.rs:236:30
    |
 LL |             let _: [u8; 2] = std::mem::transmute(0.0f16);
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0.0f16.to_ne_bytes()`
 
 error: transmute from a `f32` to a `[u8; 4]`
-  --> tests/ui/transmute.rs:238:30
+  --> tests/ui/transmute.rs:239:30
    |
 LL |             let _: [u8; 4] = std::mem::transmute(0.0f32);
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0.0f32.to_ne_bytes()`
 
 error: transmute from a `f64` to a `[u8; 8]`
-  --> tests/ui/transmute.rs:241:30
+  --> tests/ui/transmute.rs:242:30
    |
 LL |             let _: [u8; 8] = std::mem::transmute(0.0f64);
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0.0f64.to_ne_bytes()`
 
 error: transmute from a `f128` to a `[u8; 16]`
-  --> tests/ui/transmute.rs:244:31
+  --> tests/ui/transmute.rs:245:31
    |
 LL |             let _: [u8; 16] = std::mem::transmute(0.0f128);
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `to_ne_bytes()`: `0.0f128.to_ne_bytes()`
 
 error: transmute from a `&[u8]` to a `&str`
-  --> tests/ui/transmute.rs:253:28
+  --> tests/ui/transmute.rs:254:28
    |
 LL |     let _: &str = unsafe { std::mem::transmute(B) };
    |                            ^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `std::str::from_utf8(B).unwrap()`
@@ -329,13 +329,13 @@ LL |     let _: &str = unsafe { std::mem::transmute(B) };
    = help: to override `-D warnings` add `#[allow(clippy::transmute_bytes_to_str)]`
 
 error: transmute from a `&mut [u8]` to a `&mut str`
-  --> tests/ui/transmute.rs:256:32
+  --> tests/ui/transmute.rs:257:32
    |
 LL |     let _: &mut str = unsafe { std::mem::transmute(mb) };
    |                                ^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `std::str::from_utf8_mut(mb).unwrap()`
 
 error: transmute from a `&[u8]` to a `&str`
-  --> tests/ui/transmute.rs:259:30
+  --> tests/ui/transmute.rs:260:30
    |
 LL |     const _: &str = unsafe { std::mem::transmute(B) };
    |                              ^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `std::str::from_utf8_unchecked(B)`
diff --git a/src/tools/clippy/tests/ui/transmute_float_to_int.fixed b/src/tools/clippy/tests/ui/transmute_float_to_int.fixed
index 1f97b997eaa..844445907d7 100644
--- a/src/tools/clippy/tests/ui/transmute_float_to_int.fixed
+++ b/src/tools/clippy/tests/ui/transmute_float_to_int.fixed
@@ -1,5 +1,5 @@
 #![warn(clippy::transmute_float_to_int)]
-#![allow(clippy::missing_transmute_annotations)]
+#![allow(clippy::missing_transmute_annotations, unnecessary_transmutes)]
 #![feature(f128)]
 #![feature(f16)]
 
diff --git a/src/tools/clippy/tests/ui/transmute_float_to_int.rs b/src/tools/clippy/tests/ui/transmute_float_to_int.rs
index 788a7e1026c..a1f3b15bbfe 100644
--- a/src/tools/clippy/tests/ui/transmute_float_to_int.rs
+++ b/src/tools/clippy/tests/ui/transmute_float_to_int.rs
@@ -1,5 +1,5 @@
 #![warn(clippy::transmute_float_to_int)]
-#![allow(clippy::missing_transmute_annotations)]
+#![allow(clippy::missing_transmute_annotations, unnecessary_transmutes)]
 #![feature(f128)]
 #![feature(f16)]
 
diff --git a/src/tools/clippy/tests/ui/transmute_int_to_char.fixed b/src/tools/clippy/tests/ui/transmute_int_to_char.fixed
index b5425a2e9e8..28644aa9ebb 100644
--- a/src/tools/clippy/tests/ui/transmute_int_to_char.fixed
+++ b/src/tools/clippy/tests/ui/transmute_int_to_char.fixed
@@ -1,5 +1,5 @@
 #![warn(clippy::transmute_int_to_char)]
-#![allow(clippy::missing_transmute_annotations)]
+#![allow(clippy::missing_transmute_annotations, unnecessary_transmutes)]
 
 fn int_to_char() {
     let _: char = unsafe { std::char::from_u32(0_u32).unwrap() };
diff --git a/src/tools/clippy/tests/ui/transmute_int_to_char.rs b/src/tools/clippy/tests/ui/transmute_int_to_char.rs
index b24bb177c9f..8c83ecc8914 100644
--- a/src/tools/clippy/tests/ui/transmute_int_to_char.rs
+++ b/src/tools/clippy/tests/ui/transmute_int_to_char.rs
@@ -1,5 +1,5 @@
 #![warn(clippy::transmute_int_to_char)]
-#![allow(clippy::missing_transmute_annotations)]
+#![allow(clippy::missing_transmute_annotations, unnecessary_transmutes)]
 
 fn int_to_char() {
     let _: char = unsafe { std::mem::transmute(0_u32) };
diff --git a/src/tools/clippy/tests/ui/transmute_int_to_char_no_std.fixed b/src/tools/clippy/tests/ui/transmute_int_to_char_no_std.fixed
index e525751e306..e6e09a2be4b 100644
--- a/src/tools/clippy/tests/ui/transmute_int_to_char_no_std.fixed
+++ b/src/tools/clippy/tests/ui/transmute_int_to_char_no_std.fixed
@@ -1,7 +1,7 @@
 #![no_std]
 #![feature(lang_items)]
 #![warn(clippy::transmute_int_to_char)]
-#![allow(clippy::missing_transmute_annotations)]
+#![allow(clippy::missing_transmute_annotations, unnecessary_transmutes)]
 
 use core::panic::PanicInfo;
 
diff --git a/src/tools/clippy/tests/ui/transmute_int_to_char_no_std.rs b/src/tools/clippy/tests/ui/transmute_int_to_char_no_std.rs
index 7cb508ceaf3..0f2106df00e 100644
--- a/src/tools/clippy/tests/ui/transmute_int_to_char_no_std.rs
+++ b/src/tools/clippy/tests/ui/transmute_int_to_char_no_std.rs
@@ -1,7 +1,7 @@
 #![no_std]
 #![feature(lang_items)]
 #![warn(clippy::transmute_int_to_char)]
-#![allow(clippy::missing_transmute_annotations)]
+#![allow(clippy::missing_transmute_annotations, unnecessary_transmutes)]
 
 use core::panic::PanicInfo;
 
diff --git a/src/tools/miri/tests/fail/validity/invalid_bool.rs b/src/tools/miri/tests/fail/validity/invalid_bool.rs
index 4f11bb2629f..bd448af834d 100644
--- a/src/tools/miri/tests/fail/validity/invalid_bool.rs
+++ b/src/tools/miri/tests/fail/validity/invalid_bool.rs
@@ -1,3 +1,4 @@
+#![allow(unnecessary_transmutes)]
 fn main() {
     let _b = unsafe { std::mem::transmute::<u8, bool>(2) }; //~ ERROR: expected a boolean
 }
diff --git a/src/tools/miri/tests/fail/validity/invalid_bool_op.rs b/src/tools/miri/tests/fail/validity/invalid_bool_op.rs
index fe9bb3bed7f..0cbe2d76dc6 100644
--- a/src/tools/miri/tests/fail/validity/invalid_bool_op.rs
+++ b/src/tools/miri/tests/fail/validity/invalid_bool_op.rs
@@ -2,6 +2,7 @@
 // Make sure we find these even with many checks disabled.
 //@compile-flags: -Zmiri-disable-alignment-check -Zmiri-disable-stacked-borrows -Zmiri-disable-validation
 
+#![allow(unnecessary_transmutes)]
 fn main() {
     let b = unsafe { std::mem::transmute::<u8, bool>(2) };
     let _x = b == std::hint::black_box(true); //~ ERROR: interpreting an invalid 8-bit value as a bool
diff --git a/src/tools/miri/tests/fail/validity/invalid_char.rs b/src/tools/miri/tests/fail/validity/invalid_char.rs
index 568892e5910..d57c933dac1 100644
--- a/src/tools/miri/tests/fail/validity/invalid_char.rs
+++ b/src/tools/miri/tests/fail/validity/invalid_char.rs
@@ -1,3 +1,4 @@
+#![allow(unnecessary_transmutes)]
 fn main() {
     assert!(std::char::from_u32(-1_i32 as u32).is_none());
     let _val = match unsafe { std::mem::transmute::<i32, char>(-1) } {
diff --git a/src/tools/miri/tests/fail/validity/invalid_char_op.rs b/src/tools/miri/tests/fail/validity/invalid_char_op.rs
index 69924822944..e3a5f837e18 100644
--- a/src/tools/miri/tests/fail/validity/invalid_char_op.rs
+++ b/src/tools/miri/tests/fail/validity/invalid_char_op.rs
@@ -2,6 +2,7 @@
 // Make sure we find these even with many checks disabled.
 //@compile-flags: -Zmiri-disable-alignment-check -Zmiri-disable-stacked-borrows -Zmiri-disable-validation
 
+#![allow(unnecessary_transmutes)]
 fn main() {
     let c = 0xFFFFFFu32;
     assert!(std::char::from_u32(c).is_none());
diff --git a/src/tools/miri/tests/pass/float.rs b/src/tools/miri/tests/pass/float.rs
index cd60b6bd563..575d70579a4 100644
--- a/src/tools/miri/tests/pass/float.rs
+++ b/src/tools/miri/tests/pass/float.rs
@@ -6,6 +6,7 @@
 #![feature(f16)]
 #![allow(arithmetic_overflow)]
 #![allow(internal_features)]
+#![allow(unnecessary_transmutes)]
 
 use std::any::type_name;
 use std::cmp::min;
diff --git a/src/tools/miri/tests/pass/issues/issue-miri-184.rs b/src/tools/miri/tests/pass/issues/issue-miri-184.rs
index 39c841403ef..964d850298f 100644
--- a/src/tools/miri/tests/pass/issues/issue-miri-184.rs
+++ b/src/tools/miri/tests/pass/issues/issue-miri-184.rs
@@ -1,3 +1,4 @@
+#![allow(unnecessary_transmutes)]
 pub fn main() {
     let bytes: [u8; 8] = unsafe { ::std::mem::transmute(0u64) };
     let _val: &[u8] = &bytes;
diff --git a/src/tools/miri/tests/pass/shims/x86/intrinsics-x86-gfni.rs b/src/tools/miri/tests/pass/shims/x86/intrinsics-x86-gfni.rs
index a629e2acfe9..882b5e3f795 100644
--- a/src/tools/miri/tests/pass/shims/x86/intrinsics-x86-gfni.rs
+++ b/src/tools/miri/tests/pass/shims/x86/intrinsics-x86-gfni.rs
@@ -368,7 +368,7 @@ unsafe fn load_m256i_word<T>(data: &[T], word_index: usize) -> __m256i {
 #[target_feature(enable = "avx512f")]
 unsafe fn load_m512i_word<T>(data: &[T], word_index: usize) -> __m512i {
     let byte_offset = word_index * 64 / size_of::<T>();
-    let pointer = data.as_ptr().add(byte_offset) as *const i32;
+    let pointer = data.as_ptr().add(byte_offset) as *const __m512i;
     _mm512_loadu_si512(black_box(pointer))
 }
 
diff --git a/src/tools/miri/tests/pass/shims/x86/intrinsics-x86-sse.rs b/src/tools/miri/tests/pass/shims/x86/intrinsics-x86-sse.rs
index 6f7ab3b3c9f..be3f961e10f 100644
--- a/src/tools/miri/tests/pass/shims/x86/intrinsics-x86-sse.rs
+++ b/src/tools/miri/tests/pass/shims/x86/intrinsics-x86-sse.rs
@@ -1,5 +1,6 @@
 // We're testing x86 target specific features
 //@only-target: x86_64 i686
+#![allow(unnecessary_transmutes)]
 
 #[cfg(target_arch = "x86")]
 use std::arch::x86::*;