liquidfun beta regression

[est31]

The liquidfun crate version 0.8.0 fails to build on latest beta 1.21, while the build works on stable. The error output (full log):

error[E0106]: missing lifetime specifier
   --> src/box2d/dynamics/body.rs:110:49
    |
110 |     fn b2Body_GetPosition(this: *mut B2Body) -> &Vec2;
    |                                                 ^ expected lifetime parameter
    |
    = help: this function's return type contains a borrowed value with an elided lifetime, but the lifetime cannot be derived from the arguments
    = help: consider giving it an explicit bounded or 'static lifetime

cc @rjanicek

[est31]

Bisected to e40dc66 -- #43651 cc @petrochenkov @eddyb

[est31]

Minimal reproducing example:

extern {
    fn foo(this: *mut u8) -> &u32;
}

[arielb1]

I believe this is intentional.

[nikomatsakis]

This is a bug-fix, so closing as "behaving as expected". In particular, the elision rules specify that references in return types are supposed to have explicit lifetimes unless they can take their lifetime from the function parameters -- as there are no references in the function parameter list, then this is an error. (Also, we did a clean cargobomb run here, so this doesn't seem like a widespread problem.)