Also, small grammar fix.

because we are already marking unions `NoPropagation` in
`CanConstProp::check()`. That is enough to prevent any attempts
at const propagating unions and this second check is not needed.

Also improve a comment in `CanConstProp::check()`

…37-example-code, r=fmease

Mention Both HRTB and Generic Lifetime Param in `E0637` documentation

The compiler (rustc 1.77.0) error for `and_without_explicit_lifetime()` in the erroneous code example suggests using a HRTB. But, the corrected example uses an explicit lifetime parameter.

This PR fixes it so that the documentation and the compiler suggestion for error code `E0637` are consistent with each other.

…e1-dead

Remove many `#[macro_use] extern crate foo` items

This requires the addition of more `use` items, which often make the code more verbose. But they also make the code easier to read, because `#[macro_use]` obscures where macros are defined.

r? `@fee1-dead`

…-obk

Remove redundant union check in `KnownPanicsLint` const prop

Removes the below check which prevents unions from being const propagated:https://github.com/rust-lang/rust/blob/f9dca46218d4b8efa062aec4fd0820cbb4942aa2/compiler/rustc_mir_transform/src/known_panics_lint.rs#L587-L594

It is not needed because after PR rust-lang#124504 we mark unions as `NoPropagation` over here: https://github.com/rust-lang/rust/blob/f9dca46218d4b8efa062aec4fd0820cbb4942aa2/compiler/rustc_mir_transform/src/known_panics_lint.rs#L899-L902 which is enough to prevent them from being const propagated.