pub extern "rust-intrinsic" fn rustc_peek<T>(_: T) -> T
Magic intrinsic that derives its meaning from attributes attached to the function.
For example, dataflow uses this to inject static assertions so
rustc_peek(potentially_uninitialized) would actually
double-check that dataflow did indeed compute that it is
uninitialized at that point in the control flow.
This intrinsic should not be used outside of the compiler.