DestructionScopeData can leak into error messages

[arielb1]

pub trait Resources<'a> {}

pub trait Buffer<'a, R: Resources<'a>> {
    fn select(&self) -> BufferViewHandle<R>; // should be BufferViewHandle<'a, R>
}

pub struct BufferViewHandle<'a, R: 'a+Resources<'a>>(&'a R);

fn main() {}

Post-RFC1214, this gives the not-particularly-comprehensible error message

<anon>:6:5: 6:45 error: mismatched types:
 expected `Resources<'_>`,
    found `Resources<'a>`
(lifetime mismatch) [E0308]
<anon>:6     fn select(&self) -> BufferViewHandle<R>;
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<anon>:6:5: 6:45 help: see the detailed explanation for E0308
note: the anonymous lifetime #1 defined on unknown free region bounded by scope DestructionScopeData { node_id: 9 }...
note: ...does not necessarily outlive the lifetime 'a as defined on unknown free region bounded by scope DestructionScopeData { node_id: 9 }
<anon>:6:5: 6:45 error: mismatched types:
 expected `Resources<'_>`,
    found `Resources<'a>`
(lifetime mismatch) [E0308]
<anon>:6     fn select(&self) -> BufferViewHandle<R>;
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<anon>:6:5: 6:45 help: see the detailed explanation for E0308
note: the lifetime 'a as defined on unknown free region bounded by scope DestructionScopeData { node_id: 9 }...
note: ...does not necessarily outlive the anonymous lifetime #1 defined on unknown free region bounded by scope DestructionScopeData { node_id: 9 }
error: aborting due to 2 previous errors

In general, debug output of compiler structs shouldn't leak into error messages (also see #13998).

[Eh2406]

There is a FIXME related to this issue,
https://github.com/rust-lang/rust/blob/master/src/librustc/infer/error_reporting/mod.rs#L215
Now that the issue is closed can the FIXME be fix, or made more specific?