Rollup merge of #153401 - GuillaumeGomez:migrate-diag, r=JonathanBrouwer

Migrationg of `LintDiagnostic` - part 7

Part of https://github.com/rust-lang/rust/issues/153099.

This PR removes the `LintDiagnostic` trait and proc-macro. \o/

r? @JonathanBrouwer

compiler/rustc_errors/src/decorate_diag.rs

@@ -7,7 +7,7 @@
 
 use crate::{Diag, DiagCtxtHandle, Diagnostic, Level};
 
-/// We can't implement `LintDiagnostic` for `BuiltinLintDiag`, because decorating some of its
+/// We can't implement `Diagnostic` for `BuiltinLintDiag`, because decorating some of its
 /// variants requires types we don't have yet. So, handle that case separately.
 pub enum DecorateDiagCompat {
     Dynamic(Box<dyn for<'a> FnOnce(DiagCtxtHandle<'a>, Level) -> Diag<'a, ()> + DynSend + 'static>),

compiler/rustc_errors/src/diagnostic.rs

@@ -138,14 +138,6 @@ pub trait Subdiagnostic
     fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>);
 }
 
-/// Trait implemented by lint types. This should not be implemented manually. Instead, use
-/// `#[derive(LintDiagnostic)]` -- see [rustc_macros::LintDiagnostic].
-#[rustc_diagnostic_item = "LintDiagnostic"]
-pub trait LintDiagnostic<'a, G: EmissionGuarantee> {
-    /// Decorate a lint with the information from this type.
-    fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, G>);
-}
-
 #[derive(Clone, Debug, Encodable, Decodable)]
 pub(crate) struct DiagLocation {
     file: Cow<'static, str>,

compiler/rustc_errors/src/lib.rs

@@ -38,7 +38,7 @@
 pub use decorate_diag::{BufferedEarlyLint, DecorateDiagCompat, LintBuffer};
 pub use diagnostic::{
     BugAbort, Diag, DiagInner, DiagStyledString, Diagnostic, EmissionGuarantee, FatalAbort,
-    LintDiagnostic, StringPart, Subdiag, Subdiagnostic,
+    StringPart, Subdiag, Subdiagnostic,
 };
 pub use diagnostic_impls::{
     DiagSymbolList, ElidedLifetimeInPathSubdiag, ExpectedLifetimeParameter,