`transmute-ptr-to-ptr` suggested path does not work

Using the following flags

--force-warn clippy::transmute-ptr-to-ptr

this code:

fn bidirectional_subtyping() {
    // Test that transmuting between subtypes of dyn traits is fine, even in the
    // "wrong direction", i.e. going from a lower-ranked to a higher-ranked dyn trait.
    // Note that compared to the `dyn-transmute-inner-binder` test, the `for` is on the
    // *outside* here!

    trait Trait<U: ?Sized> {}
    impl<T, U: ?Sized> Trait<U> for T {}

    struct Wrapper<T: ?Sized>(T);

    let x: &dyn Trait<fn(&'static ())> = &();
    let _y: &dyn for<'a> Trait<fn(&'a ())> = unsafe { std::mem::transmute(x) };

    let x: &dyn for<'a> Trait<fn(&'a ())> = &();
    let _y: &dyn Trait<fn(&'static ())> = unsafe { std::mem::transmute(x) };

    let x: &dyn Trait<dyn Trait<fn(&'static ())>> = &();
    let _y: &dyn for<'a> Trait<dyn Trait<fn(&'a ())>> = unsafe { std::mem::transmute(x) };

    let x: &dyn for<'a> Trait<dyn Trait<fn(&'a ())>> = &();
    let _y: &dyn Trait<dyn Trait<fn(&'static ())>> = unsafe { std::mem::transmute(x) };

    // This lowers to a ptr-to-ptr cast (which behaves like a transmute)
    // and not an unsizing coercion:
    let x: *const dyn for<'a> Trait<&'a ()> = &();
    let _y: *const Wrapper<dyn Trait<&'static ()>> = x as _;
}

caused the following diagnostics:

    Checking _a v0.1.0 (/tmp/icemaker_global_tempdir.OhkT1XoKk8t8/icemaker_clippyfix_tempdir.sfnw4ze5vQKV/_a)
warning: transmute from a reference to a reference
  --> src/lib.rs:13:55
   |
13 |     let _y: &dyn for<'a> Trait<fn(&'a ())> = unsafe { std::mem::transmute(x) };
   |                                                       ^^^^^^^^^^^^^^^^^^^^^^ help: try: `&*(x as *const dyn bidirectional_subtyping::Trait<fn(&())> as *const dyn for<'a> bidirectional_subtyping::Trait<fn(&'a ())>)`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#transmute_ptr_to_ptr
   = note: requested on the command line with `--force-warn clippy::transmute-ptr-to-ptr`

warning: transmute from a reference to a reference
  --> src/lib.rs:16:52
   |
16 |     let _y: &dyn Trait<fn(&'static ())> = unsafe { std::mem::transmute(x) };
   |                                                    ^^^^^^^^^^^^^^^^^^^^^^ help: try: `&*(x as *const dyn for<'a> bidirectional_subtyping::Trait<fn(&'a ())> as *const dyn bidirectional_subtyping::Trait<fn(&())>)`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#transmute_ptr_to_ptr

warning: transmute from a reference to a reference
  --> src/lib.rs:19:66
   |
19 |     let _y: &dyn for<'a> Trait<dyn Trait<fn(&'a ())>> = unsafe { std::mem::transmute(x) };
   |                                                                  ^^^^^^^^^^^^^^^^^^^^^^ help: try: `&*(x as *const dyn bidirectional_subtyping::Trait<dyn bidirectional_subtyping::Trait<fn(&())>> as *const dyn for<'a> bidirectional_subtyping::Trait<dyn bidirectional_subtyping::Trait<fn(&'a ())>>)`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#transmute_ptr_to_ptr

warning: transmute from a reference to a reference
  --> src/lib.rs:22:63
   |
22 |     let _y: &dyn Trait<dyn Trait<fn(&'static ())>> = unsafe { std::mem::transmute(x) };
   |                                                               ^^^^^^^^^^^^^^^^^^^^^^ help: try: `&*(x as *const dyn for<'a> bidirectional_subtyping::Trait<dyn bidirectional_subtyping::Trait<fn(&'a ())>> as *const dyn bidirectional_subtyping::Trait<dyn bidirectional_subtyping::Trait<fn(&())>>)`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#transmute_ptr_to_ptr

warning: `_a` (lib) generated 4 warnings
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.23s

However after applying these diagnostics, the resulting code:

fn bidirectional_subtyping() {
    // Test that transmuting between subtypes of dyn traits is fine, even in the
    // "wrong direction", i.e. going from a lower-ranked to a higher-ranked dyn trait.
    // Note that compared to the `dyn-transmute-inner-binder` test, the `for` is on the
    // *outside* here!

    trait Trait<U: ?Sized> {}
    impl<T, U: ?Sized> Trait<U> for T {}

    struct Wrapper<T: ?Sized>(T);

    let x: &dyn Trait<fn(&'static ())> = &();
    let _y: &dyn for<'a> Trait<fn(&'a ())> = unsafe { &*(x as *const dyn bidirectional_subtyping::Trait<fn(&())> as *const dyn for<'a> bidirectional_subtyping::Trait<fn(&'a ())>) };

    let x: &dyn for<'a> Trait<fn(&'a ())> = &();
    let _y: &dyn Trait<fn(&'static ())> = unsafe { &*(x as *const dyn for<'a> bidirectional_subtyping::Trait<fn(&'a ())> as *const dyn bidirectional_subtyping::Trait<fn(&())>) };

    let x: &dyn Trait<dyn Trait<fn(&'static ())>> = &();
    let _y: &dyn for<'a> Trait<dyn Trait<fn(&'a ())>> = unsafe { &*(x as *const dyn bidirectional_subtyping::Trait<dyn bidirectional_subtyping::Trait<fn(&())>> as *const dyn for<'a> bidirectional_subtyping::Trait<dyn bidirectional_subtyping::Trait<fn(&'a ())>>) };

    let x: &dyn for<'a> Trait<dyn Trait<fn(&'a ())>> = &();
    let _y: &dyn Trait<dyn Trait<fn(&'static ())>> = unsafe { &*(x as *const dyn for<'a> bidirectional_subtyping::Trait<dyn bidirectional_subtyping::Trait<fn(&'a ())>> as *const dyn bidirectional_subtyping::Trait<dyn bidirectional_subtyping::Trait<fn(&())>>) };

    // This lowers to a ptr-to-ptr cast (which behaves like a transmute)
    // and not an unsizing coercion:
    let x: *const dyn for<'a> Trait<&'a ()> = &();
    let _y: *const Wrapper<dyn Trait<&'static ()>> = x as _;
}

no longer compiled:

    Checking _a v0.1.0 (/tmp/icemaker_global_tempdir.OhkT1XoKk8t8/icemaker_clippyfix_tempdir.sfnw4ze5vQKV/_a)
error[E0433]: failed to resolve: function `bidirectional_subtyping` is not a crate or module
  --> src/lib.rs:13:74
   |
13 | ...afe { &*(x as *const dyn bidirectional_subtyping::Trait<fn(&())> as *const dyn for<'a> bidirectional_subtyping::Trait<fn(&'a ())>) };
   |                             ^^^^^^^^^^^^^^^^^^^^^^^ function `bidirectional_subtyping` is not a crate or module

error[E0433]: failed to resolve: function `bidirectional_subtyping` is not a crate or module
  --> src/lib.rs:13:136
   |
13 | ...)> as *const dyn for<'a> bidirectional_subtyping::Trait<fn(&'a ())>) };
   |                             ^^^^^^^^^^^^^^^^^^^^^^^ function `bidirectional_subtyping` is not a crate or module

error[E0433]: failed to resolve: function `bidirectional_subtyping` is not a crate or module
  --> src/lib.rs:16:79
   |
16 | ...(x as *const dyn for<'a> bidirectional_subtyping::Trait<fn(&'a ())> as *const dyn bidirectional_subtyping::Trait<fn(&())>) };
   |                             ^^^^^^^^^^^^^^^^^^^^^^^ function `bidirectional_subtyping` is not a crate or module

error[E0433]: failed to resolve: function `bidirectional_subtyping` is not a crate or module
  --> src/lib.rs:16:136
   |
16 | ...n(&'a ())> as *const dyn bidirectional_subtyping::Trait<fn(&())>) };
   |                             ^^^^^^^^^^^^^^^^^^^^^^^ function `bidirectional_subtyping` is not a crate or module

error[E0433]: failed to resolve: function `bidirectional_subtyping` is not a crate or module
  --> src/lib.rs:19:85
   |
19 | ...afe { &*(x as *const dyn bidirectional_subtyping::Trait<dyn bidirectional_subtyping::Trait<fn(&())>> as *const dyn for<'a> bidirection...
   |                             ^^^^^^^^^^^^^^^^^^^^^^^ function `bidirectional_subtyping` is not a crate or module

error[E0433]: failed to resolve: function `bidirectional_subtyping` is not a crate or module
  --> src/lib.rs:19:120
   |
19 | ...nal_subtyping::Trait<dyn bidirectional_subtyping::Trait<fn(&())>> as *const dyn for<'a> bidirectional_subtyping::Trait<dyn bidirection...
   |                             ^^^^^^^^^^^^^^^^^^^^^^^ function `bidirectional_subtyping` is not a crate or module

error[E0433]: failed to resolve: function `bidirectional_subtyping` is not a crate or module
  --> src/lib.rs:19:183
   |
19 | ...>> as *const dyn for<'a> bidirectional_subtyping::Trait<dyn bidirectional_subtyping::Trait<fn(&'a ())>>) };
   |                             ^^^^^^^^^^^^^^^^^^^^^^^ function `bidirectional_subtyping` is not a crate or module

error[E0433]: failed to resolve: function `bidirectional_subtyping` is not a crate or module
  --> src/lib.rs:19:218
   |
19 | ...nal_subtyping::Trait<dyn bidirectional_subtyping::Trait<fn(&'a ())>>) };
   |                             ^^^^^^^^^^^^^^^^^^^^^^^ function `bidirectional_subtyping` is not a crate or module

error[E0433]: failed to resolve: function `bidirectional_subtyping` is not a crate or module
  --> src/lib.rs:22:90
   |
22 | ...(x as *const dyn for<'a> bidirectional_subtyping::Trait<dyn bidirectional_subtyping::Trait<fn(&'a ())>> as *const dyn bidirectional_su...
   |                             ^^^^^^^^^^^^^^^^^^^^^^^ function `bidirectional_subtyping` is not a crate or module

error[E0433]: failed to resolve: function `bidirectional_subtyping` is not a crate or module
  --> src/lib.rs:22:125
   |
22 | ...nal_subtyping::Trait<dyn bidirectional_subtyping::Trait<fn(&'a ())>> as *const dyn bidirectional_subtyping::Trait<dyn bidirectional_su...
   |                             ^^^^^^^^^^^^^^^^^^^^^^^ function `bidirectional_subtyping` is not a crate or module

error[E0433]: failed to resolve: function `bidirectional_subtyping` is not a crate or module
  --> src/lib.rs:22:183
   |
22 | ...(&'a ())>> as *const dyn bidirectional_subtyping::Trait<dyn bidirectional_subtyping::Trait<fn(&())>>) };
   |                             ^^^^^^^^^^^^^^^^^^^^^^^ function `bidirectional_subtyping` is not a crate or module

error[E0433]: failed to resolve: function `bidirectional_subtyping` is not a crate or module
  --> src/lib.rs:22:218
   |
22 | ...nal_subtyping::Trait<dyn bidirectional_subtyping::Trait<fn(&())>>) };
   |                             ^^^^^^^^^^^^^^^^^^^^^^^ function `bidirectional_subtyping` is not a crate or module

For more information about this error, try `rustc --explain E0433`.
error: could not compile `_a` (lib test) due to 12 previous errors
warning: build failed, waiting for other jobs to finish...
error: could not compile `_a` (lib) due to 12 previous errors

Version:

rustc 1.92.0-nightly (4a54b26d3 2025-10-07)
binary: rustc
commit-hash: 4a54b26d30dac43778afb0e503524b763fce0eee
commit-date: 2025-10-07
host: x86_64-unknown-linux-gnu
release: 1.92.0-nightly
LLVM version: 21.1.2

Start by reproducing the transmute-ptr-to-ptr warning from the issue with the provided nightly Rust version, then locate the lint code that constructs its replacement suggestion. The fix is complete when the suggested code compiles for the shown local trait cases and the existing lint tests cover this behavior.