Extend `proc_macro_back_compat` lint to `procedural-masquerade`

We now lint on *any* use of `procedural-masquerade` crate. While this
crate still exists, its main reverse dependency (`cssparser`) no longer
depends on it. Any crates still depending off should stop doing so, as
it only exists to support very old Rust versions.

If a crate actually needs to support old versions of rustc via
`procedural-masquerade`, then they'll just need to accept the warning
until we remove it entirely (at the same time as the back-compat hack).
The latest version of `procedural-masquerade` does not work with the
latest rustc, but trying to check for the version seems like more
trouble than it's worth.

While working on this, I realized that the `proc-macro-hack` check was
never actually doing anything. The corresponding enum variant in
`proc-macro-hack` is named `Value` or `Nested` - it has never been
called `Input`. Due to a strange Crater issue, the Crater run that
tested adding this did *not* end up testing it - some of the crates that
would have failed did not actually have their tests checked, making it
seem as though the `proc-macro-hack` check was working.

The Crater issue is being discussed at
https://rust-lang.zulipchat.com/#narrow/stream/242791-t-infra/topic/Nearly.20identical.20Crater.20runs.20processed.20a.20crate.20differently/near/230406661

Despite the `proc-macro-hack` check not actually doing anything, we
haven't gotten any reports from users about their build being broken.
I went ahead and removed it entirely, since it's clear that no one is
being affected by the `proc-macro-hack` regression in practice.

1 files changed, 2 insertions, 1 deletions

diff --git a/compiler/rustc_expand/src/proc_macro.rs b/compiler/rustc_expand/src/proc_macro.rs
index 8cbaa7c945a..61b776ff2d2 100644
--- a/compiler/rustc_expand/src/proc_macro.rs
+++ b/compiler/rustc_expand/src/proc_macro.rs
@@ -90,7 +90,8 @@ impl MultiItemModifier for ProcMacroDerive {
             }
             _ => unreachable!(),
         };
-        let input = if item.pretty_printing_compatibility_hack() {
+        let input = if crate::base::pretty_printing_compatibility_hack(&item, &ecx.sess.parse_sess)
+        {
             TokenTree::token(token::Interpolated(Lrc::new(item)), DUMMY_SP).into()
         } else {
             nt_to_tokenstream(&item, &ecx.sess.parse_sess, CanSynthesizeMissingTokens::Yes)