Deny when pointer to temporary stored somewhere

What it does

It should deny this code:

struct MyStruct{
   field: usize
}

let my_struct_ptr: *mut MyStruct = ...;
let reference_to_field = &mut unsafe { (*my_struct_ptr).field };
// use reference here

This code actually creates temporary with value of field, takes reference to it, then drops temporary.
Therefore here we have dangling pointer to stack.

It should suggest this:

let reference_to_field = unsafe { &mut (*my_struct_ptr).field };

Categories (optional)

• Kind: clippy::correctness
• Remove UB code created in unsafe block

Drawbacks

None.

Example

let reference_to_field = &mut unsafe { (*my_struct_ptr).field };

Should be written as:

let reference_to_field = unsafe { &mut (*my_struct_ptr).field };

Also

Link to issue which caused by original code: https://github.com/Morganamilo/paru/issues/392
Bugfix: https://github.com/archlinux/alpm.rs/commit/5253d6
Relevant Reddit discussion.

Start by reproducing the two Rust examples and search rust-clippy's correctness lints for the relevant implementation entry point. The work is done when the first form is denied as a dangling reference risk and the second form is accepted, with the suggested rewrite matching the issue.