Mir undefined behaviour false positive when comparing Option<&T> #55454

#[derive(PartialEq, Debug)]
struct Cons<H, T: Hlist> {
    head: H,
    tail: T
}

#[derive(PartialEq, Debug)]
struct Nil;

trait Hlist {}
impl<H, T: Hlist> Hlist for Cons<H, T> {}
impl Hlist for Nil {}

fn main() {

    // This part works fine
    let x = Cons {head: Some(&0), tail: Nil};
    let y = Cons {head: Some(&0), tail: Nil};
    assert_eq!(x, y);

    // This apparently-equivalent code fails to compile (passes cargo-check but not cargo-build)
    assert_eq!(
        Cons {head: Some(&0), tail: Nil},
        Cons {head: Some(&0), tail: Nil}
    );
}

➜  rustup default stable
info: using existing install for 'stable-x86_64-unknown-linux-gnu'
info: default toolchain set to 'stable-x86_64-unknown-linux-gnu'

  stable-x86_64-unknown-linux-gnu unchanged - rustc 1.30.0 (da5f414c2 2018-10-24)

➜ cargo build
    Finished dev [unoptimized + debuginfo] target(s) in 0.12s    

➜  rustup default nightly
info: using existing install for 'nightly-x86_64-unknown-linux-gnu'
info: default toolchain set to 'nightly-x86_64-unknown-linux-gnu'

  nightly-x86_64-unknown-linux-gnu unchanged - rustc 1.31.0-nightly (cae6efc37 2018-10-27)

➜  cargo build
   Compiling typeck v0.1.0                                               
error[E0080]: it is undefined behavior to use this value                                                
  --> src/main.rs:15:1                                                                                  
   |                                                                                                    
15 | / fn main() {                                                                                      
16 | |                                                                                                  
17 | |     // This part works fine                                                                      
18 | |     let x = Cons {head: Some(&0), tail: Nil};                                                    
...  |                                                                                                  
26 | |     );                                                                                           
27 | | }                                                                                                
   | |_^ type validation failed: encountered a pointer, but expected something that cannot possibly be outside the (wrapping) range 1..=0
   |                                                                                                    
   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
                                                                                                        
error: aborting due to previous error                                                                   
                                                                                                        
For more information about this error, try `rustc --explain E0080`.                                     
error: Could not compile `typeck`.                                                                      

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