#1 attempt to pass physics world by reference

[Vrixyz]

See #1 for context details.

I succeeded in crashing the compiler.

Output of cargo run --verbose :

   Compiling testbed_callback v0.1.0 (file:///Users/***/Documents/perso/testbed-callback)
     Running `rustc --crate-name testbed_callback src/main.rs --crate-type bin --emit=dep-info,link -C debuginfo=2 -C metadata=8c68544d0e3087a8 -C extra-filename=-8c68544d0e3087a8 --out-dir /Users/***/Documents/perso/testbed-callback/target/debug/deps -C incremental=/Users/***/Documents/perso/testbed-callback/target/debug/incremental -L dependency=/Users/***/Documents/perso/testbed-callback/target/debug/deps --extern nalgebra=/Users/***/Documents/perso/testbed-callback/target/debug/deps/libnalgebra-a27da1ab88af398c.rlib --extern ncollide2d=/Users/***/Documents/perso/testbed-callback/target/debug/deps/libncollide2d-c5db2bf8d498f1fe.rlib --extern nphysics2d=/Users/***/Documents/perso/testbed-callback/target/debug/deps/libnphysics2d-fab013328e575c2c.rlib --extern nphysics_testbed2d=/Users/***/Documents/perso/testbed-callback/target/debug/deps/libnphysics_testbed2d-fd50d71f04d30a0f.rlib --extern specs=/Users/***/Documents/perso/testbed-callback/target/debug/deps/libspecs-2561d670a586ca05.rlib`
error: internal compiler error: librustc/ty/subst.rs:425: Region parameter out of range when substituting in region 'b (root type=Some((specs::Write<'a, PhysicsWorld<'b>>,))) (index=2)

thread 'main' panicked at 'Box<Any>', librustc_errors/lib.rs:517:9
note: Run with `RUST_BACKTRACE=1` for a backtrace.
error: aborting due to previous error


note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.30.0-nightly (d5a448b3f 2018-08-13) running on x86_64-apple-darwin

note: compiler flags: -C debuginfo=2 -C incremental --crate-type bin

note: some of the compiler flags provided by cargo are hidden

error: Could not compile `testbed_callback`.

Caused by:
  process didn't exit successfully: `rustc --crate-name testbed_callback src/main.rs --crate-type bin --emit=dep-info,link -C debuginfo=2 -C metadata=8c68544d0e3087a8 -C extra-filename=-8c68544d0e3087a8 --out-dir /Users/***/Documents/perso/testbed-callback/target/debug/deps -C incremental=/Users/***/Documents/perso/testbed-callback/target/debug/incremental -L dependency=/Users/***/Documents/perso/testbed-callback/target/debug/deps --extern nalgebra=/Users/***/Documents/perso/testbed-callback/target/debug/deps/libnalgebra-a27da1ab88af398c.rlib --extern ncollide2d=/Users/***/Documents/perso/testbed-callback/target/debug/deps/libncollide2d-c5db2bf8d498f1fe.rlib --extern nphysics2d=/Users/***/Documents/perso/testbed-callback/target/debug/deps/libnphysics2d-fab013328e575c2c.rlib --extern nphysics_testbed2d=/Users/***/Documents/perso/testbed-callback/target/debug/deps/libnphysics_testbed2d-fd50d71f04d30a0f.rlib --extern specs=/Users/***/Documents/perso/testbed-callback/target/debug/deps/libspecs-2561d670a586ca05.rlib` (exit code: 101)