Auto merge of #69854 - pietroalbini:stable-next, r=Centril 1.42.0

[stable] Release 1.42.0

This PR prepares the release artifacts of Rust 1.42.0, and cherry-picks the following PRs:

* https://github.com/rust-lang/rust/pull/69754: Update deprecation version to 1.42 for Error::description
* https://github.com/rust-lang/rust/pull/69753: Do not ICE when matching an uninhabited enum's field
* https://github.com/rust-lang/rust/pull/69522 / https://github.com/rust-lang/rust/pull/69853: error_derive_forbidden_on_non_adt: be more graceful
* https://github.com/rust-lang/rust/pull/68598:  Fix null synthetic_implementors error

In addition, the release notes are updated to include the remaining compatibility notes.

r? @Centril

3 files changed, 127 insertions, 0 deletions

diff --git a/src/test/ui/consts/issue-69191-ice-on-uninhabited-enum-field.rs b/src/test/ui/consts/issue-69191-ice-on-uninhabited-enum-field.rs
new file mode 100644
index 00000000000..5b7c7be42cf
--- /dev/null
+++ b/src/test/ui/consts/issue-69191-ice-on-uninhabited-enum-field.rs
@@ -0,0 +1,91 @@
+// build-pass
+//
+// (this is deliberately *not* check-pass; I have confirmed that the bug in
+// question does not replicate when one uses `cargo check` alone.)
+
+pub enum Void {}
+
+enum UninhabitedUnivariant {
+    _Variant(Void),
+}
+
+enum UninhabitedMultivariant2 {
+    _Variant(Void),
+    _Warriont(Void),
+}
+
+enum UninhabitedMultivariant3 {
+    _Variant(Void),
+    _Warriont(Void),
+    _Worrynot(Void),
+}
+
+#[repr(C)]
+enum UninhabitedUnivariantC {
+    _Variant(Void),
+}
+
+#[repr(i32)]
+enum UninhabitedUnivariant32 {
+    _Variant(Void),
+}
+
+fn main() {
+    let _seed: UninhabitedUnivariant = None.unwrap();
+    match _seed {
+        UninhabitedUnivariant::_Variant(_x) => {}
+    }
+
+    let _seed: UninhabitedMultivariant2 = None.unwrap();
+    match _seed {
+        UninhabitedMultivariant2::_Variant(_x) => {}
+        UninhabitedMultivariant2::_Warriont(_x) => {}
+    }
+
+    let _seed: UninhabitedMultivariant2 = None.unwrap();
+    match _seed {
+        UninhabitedMultivariant2::_Variant(_x) => {}
+        _ => {}
+    }
+
+    let _seed: UninhabitedMultivariant2 = None.unwrap();
+    match _seed {
+        UninhabitedMultivariant2::_Warriont(_x) => {}
+        _ => {}
+    }
+
+    let _seed: UninhabitedMultivariant3 = None.unwrap();
+    match _seed {
+        UninhabitedMultivariant3::_Variant(_x) => {}
+        UninhabitedMultivariant3::_Warriont(_x) => {}
+        UninhabitedMultivariant3::_Worrynot(_x) => {}
+    }
+
+    let _seed: UninhabitedMultivariant3 = None.unwrap();
+    match _seed {
+        UninhabitedMultivariant3::_Variant(_x) => {}
+        _ => {}
+    }
+
+    let _seed: UninhabitedMultivariant3 = None.unwrap();
+    match _seed {
+        UninhabitedMultivariant3::_Warriont(_x) => {}
+        _ => {}
+    }
+
+    let _seed: UninhabitedMultivariant3 = None.unwrap();
+    match _seed {
+        UninhabitedMultivariant3::_Worrynot(_x) => {}
+        _ => {}
+    }
+
+    let _seed: UninhabitedUnivariantC = None.unwrap();
+    match _seed {
+        UninhabitedUnivariantC::_Variant(_x) => {}
+    }
+
+    let _seed: UninhabitedUnivariant32 = None.unwrap();
+    match _seed {
+        UninhabitedUnivariant32::_Variant(_x) => {}
+    }
+}
diff --git a/src/test/ui/malformed/issue-69341-malformed-derive-inert.rs b/src/test/ui/malformed/issue-69341-malformed-derive-inert.rs
new file mode 100644
index 00000000000..24692f7cf52
--- /dev/null
+++ b/src/test/ui/malformed/issue-69341-malformed-derive-inert.rs
@@ -0,0 +1,10 @@
+fn main() {}
+
+struct CLI {
+    #[derive(parse())]
+    //~^ ERROR traits in `#[derive(...)]` don't accept arguments
+    //~| ERROR cannot find derive macro `parse` in this scope
+    //~| ERROR cannot find derive macro `parse` in this scope
+    path: (),
+    //~^ ERROR `derive` may only be applied to structs, enums and unions
+}
diff --git a/src/test/ui/malformed/issue-69341-malformed-derive-inert.stderr b/src/test/ui/malformed/issue-69341-malformed-derive-inert.stderr
new file mode 100644
index 00000000000..e8f96178d10
--- /dev/null
+++ b/src/test/ui/malformed/issue-69341-malformed-derive-inert.stderr
@@ -0,0 +1,26 @@
+error: traits in `#[derive(...)]` don't accept arguments
+  --> $DIR/issue-69341-malformed-derive-inert.rs:4:19
+   |
+LL |     #[derive(parse())]
+   |                   ^^ help: remove the arguments
+
+error: `derive` may only be applied to structs, enums and unions
+  --> $DIR/issue-69341-malformed-derive-inert.rs:8:5
+   |
+LL |     path: (),
+   |     ^^^^^^^^
+
+error: cannot find derive macro `parse` in this scope
+  --> $DIR/issue-69341-malformed-derive-inert.rs:4:14
+   |
+LL |     #[derive(parse())]
+   |              ^^^^^
+
+error: cannot find derive macro `parse` in this scope
+  --> $DIR/issue-69341-malformed-derive-inert.rs:4:14
+   |
+LL |     #[derive(parse())]
+   |              ^^^^^
+
+error: aborting due to 4 previous errors
+