introduce new lint infra

lint on duplicates during attribute parsing
To do this we stuff them in the diagnostic context to be emitted after
hir is constructed

compiler/rustc_errors/src/lib.rs

@@ -60,8 +60,9 @@ pub use rustc_error_messages::{
     SubdiagMessage, fallback_fluent_bundle, fluent_bundle,
 };
 use rustc_hashes::Hash128;
-use rustc_lint_defs::LintExpectationId;
+use rustc_hir::HirId;
 pub use rustc_lint_defs::{Applicability, listify, pluralize};
+use rustc_lint_defs::{Lint, LintExpectationId};
 use rustc_macros::{Decodable, Encodable};
 pub use rustc_span::ErrorGuaranteed;
 pub use rustc_span::fatal_error::{FatalError, FatalErrorMarker};
@@ -101,6 +102,19 @@ rustc_data_structures::static_assert_size!(PResult<'_, ()>, 24);
 #[cfg(target_pointer_width = "64")]
 rustc_data_structures::static_assert_size!(PResult<'_, bool>, 24);
 
+/// Used to avoid depending on `rustc_middle` in `rustc_attr_parsing`.
+/// Always the `TyCtxt`.
+pub trait LintEmitter: Copy {
+    #[track_caller]
+    fn emit_node_span_lint(
+        self,
+        lint: &'static Lint,
+        hir_id: HirId,
+        span: impl Into<MultiSpan>,
+        decorator: impl for<'a> LintDiagnostic<'a, ()>,
+    );
+}
+
 #[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, Encodable, Decodable)]
 pub enum SuggestionStyle {
     /// Hide the suggested code when displaying this suggestion inline.