`ref-binding-to-reference` does not pass borrowck

[matthiaskrgr]

Using the following flags

--force-warn clippy::ref-binding-to-reference

this code:

fn f1(_: &str) {}
macro_rules! m2 {
    ($e:expr) => {
        f1(*$e)
    };
}
macro_rules! m3 {
    ($i:ident) => {
        Some(ref $i)
    };
}

fn main() {
    let x = String::new();

    // Ok, the pattern is from a macro
    let _: &&String = match Some(&x) {
        m3!(x) => x,
        None => return,
    };

    // Err, reference to a &String
    let _: &&String = match Some(&x) {
        Some(ref x) => x,
        //~^ ref_binding_to_reference
        None => return,
    };
}

caused the following diagnostics:

    Checking _a v0.1.0 (/tmp/icemaker_global_tempdir.10JLGLYCNz9G/icemaker_clippyfix_tempdir.O7oZxdpBlDxD/_a)
warning: this pattern creates a reference to a reference
  --> src/main.rs:24:14
   |
24 |         Some(ref x) => x,
   |              ^^^^^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#ref_binding_to_reference
   = note: requested on the command line with `--force-warn clippy::ref-binding-to-reference`
help: try
   |
24 -         Some(ref x) => x,
24 +         Some(x) => &x,
   |

warning: `_a` (bin "_a") generated 1 warning (run `cargo clippy --fix --bin "_a"` to apply 1 suggestion)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.18s

However after applying these diagnostics, the resulting code:

fn f1(_: &str) {}
macro_rules! m2 {
    ($e:expr) => {
        f1(*$e)
    };
}
macro_rules! m3 {
    ($i:ident) => {
        Some(ref $i)
    };
}

fn main() {
    let x = String::new();

    // Ok, the pattern is from a macro
    let _: &&String = match Some(&x) {
        m3!(x) => x,
        None => return,
    };

    // Err, reference to a &String
    let _: &&String = match Some(&x) {
        Some(x) => &x,
        //~^ ref_binding_to_reference
        None => return,
    };
}

no longer compiled:

    Checking _a v0.1.0 (/tmp/icemaker_global_tempdir.10JLGLYCNz9G/icemaker_clippyfix_tempdir.O7oZxdpBlDxD/_a)
error[E0597]: `x` does not live long enough
  --> src/main.rs:24:20
   |
24 |         Some(x) => &x,
   |              -     ^-
   |              |     ||
   |              |     |`x` dropped here while still borrowed
   |              |     borrowed value does not live long enough
   |              binding `x` declared here

For more information about this error, try `rustc --explain E0597`.
error: could not compile `_a` (bin "_a" test) due to 1 previous error
warning: build failed, waiting for other jobs to finish...
error: could not compile `_a` (bin "_a") due to 1 previous error

Version:

rustc 1.90.0-nightly (c83e217d2 2025-07-06)
binary: rustc
commit-hash: c83e217d268d25960a0c79c6941bcb3917a6a0af
commit-date: 2025-07-06
host: x86_64-unknown-linux-gnu
release: 1.90.0-nightly
LLVM version: 20.1.7