transmuting between size can vary

[SimonSapin]

rustc 1.14.0-nightly (a3bc191 2016-10-10)

pub trait TypeConstructor<'a> {
    type T;
}

unsafe fn transmute_lifetime<'a, 'b, C>(x: <C as TypeConstructor<'a>>::T)
                                        -> <C as TypeConstructor<'b>>::T
where for<'z> C: TypeConstructor<'z> {
    ::std::mem::transmute(x)
}

error[E0512]: transmute called with differently sized types: <C as TypeConstructor<'a>>::T (size can vary because of <C as TypeConstructor>::T) to <C as TypeConstructor<'b>>::T (size can vary because of <C as TypeConstructor>::T)
  --> src/lib.rs:47:5
   |
47 |     ::std::mem::transmute(x)
   |     ^^^^^^^^^^^^^^^^^^^^^ transmuting between size can vary because of <C as TypeConstructor>::T and size can vary because of <C as TypeConstructor>::T

The error message near ^^^^^^ doesn’t seem grammatically correct.

[eddyb]

It's printing the message in the parens for each one but as if it's the types or something.

cc @jonathandturner