Rollup merge of #83168 - Aaron1011:lint-procedural-masquerade, r=petrochenkov

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 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.

3 files changed, 60 insertions, 0 deletions

diff --git a/src/test/ui/proc-macro/issue-73933-procedural-masquerade.rs b/src/test/ui/proc-macro/issue-73933-procedural-masquerade.rs
new file mode 100644
index 00000000000..abc3d2691a3
--- /dev/null
+++ b/src/test/ui/proc-macro/issue-73933-procedural-masquerade.rs
@@ -0,0 +1,13 @@
+// check-pass
+// aux-build:test-macros.rs
+
+#[macro_use]
+extern crate test_macros;
+
+#[derive(Print)]
+enum ProceduralMasqueradeDummyType { //~ WARN using
+//~| WARN this was previously
+    Input
+}
+
+fn main() {}
diff --git a/src/test/ui/proc-macro/issue-73933-procedural-masquerade.stderr b/src/test/ui/proc-macro/issue-73933-procedural-masquerade.stderr
new file mode 100644
index 00000000000..0b930705e35
--- /dev/null
+++ b/src/test/ui/proc-macro/issue-73933-procedural-masquerade.stderr
@@ -0,0 +1,25 @@
+warning: using `procedural-masquerade` crate
+  --> $DIR/issue-73933-procedural-masquerade.rs:8:6
+   |
+LL | enum ProceduralMasqueradeDummyType {
+   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(proc_macro_back_compat)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #83125 <https://github.com/rust-lang/rust/issues/83125>
+   = note: The `procedural-masquerade` crate has been unnecessary since Rust 1.30.0. Versions of this crate below 0.1.7 will eventually stop compiling.
+
+warning: 1 warning emitted
+
+Future incompatibility report: Future breakage date: None, diagnostic:
+warning: using `procedural-masquerade` crate
+  --> $DIR/issue-73933-procedural-masquerade.rs:8:6
+   |
+LL | enum ProceduralMasqueradeDummyType {
+   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(proc_macro_back_compat)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #83125 <https://github.com/rust-lang/rust/issues/83125>
+   = note: The `procedural-masquerade` crate has been unnecessary since Rust 1.30.0. Versions of this crate below 0.1.7 will eventually stop compiling.
+
diff --git a/src/test/ui/proc-macro/issue-73933-procedural-masquerade.stdout b/src/test/ui/proc-macro/issue-73933-procedural-masquerade.stdout
new file mode 100644
index 00000000000..8edd68f8a3b
--- /dev/null
+++ b/src/test/ui/proc-macro/issue-73933-procedural-masquerade.stdout
@@ -0,0 +1,22 @@
+PRINT-DERIVE INPUT (DISPLAY): enum ProceduralMasqueradeDummyType { Input, }
+PRINT-DERIVE RE-COLLECTED (DISPLAY): enum ProceduralMasqueradeDummyType { Input }
+PRINT-DERIVE INPUT (DEBUG): TokenStream [
+    Ident {
+        ident: "enum",
+        span: #0 bytes(100..104),
+    },
+    Ident {
+        ident: "ProceduralMasqueradeDummyType",
+        span: #0 bytes(105..134),
+    },
+    Group {
+        delimiter: Brace,
+        stream: TokenStream [
+            Ident {
+                ident: "Input",
+                span: #0 bytes(186..191),
+            },
+        ],
+        span: #0 bytes(135..193),
+    },
+]