Move UnusedDuplicate diag struct to rustc_attr_parsing

compiler/rustc_attr_parsing/src/attributes/doc.rs

@@ -22,7 +22,7 @@ use crate::diagnostics::{
 use crate::parser::{ArgParser, MetaItemOrLitParser, MetaItemParser, OwnedPathParser};
 use crate::session_diagnostics::{
     DocAliasBadChar, DocAliasEmpty, DocAliasMalformed, DocAliasStartEnd, DocAttrNotCrateLevel,
-    DocAttributeNotAttribute, DocKeywordNotKeyword,
+    DocAttributeNotAttribute, DocKeywordNotKeyword, UnusedDuplicate,
 };
 
 fn check_keyword(cx: &mut AcceptContext<'_, '_>, keyword: Symbol, span: Span) -> bool {
@@ -159,11 +159,7 @@ impl DocParser {
                     let unused_span = path.span();
                     cx.emit_lint(
                         rustc_session::lint::builtin::INVALID_DOC_ATTRIBUTES,
-                        rustc_errors::lints::UnusedDuplicate {
-                            this: unused_span,
-                            other: used_span,
-                            warning: true,
-                        },
+                        UnusedDuplicate { this: unused_span, other: used_span, warning: true },
                         unused_span,
                     );
                     return;

compiler/rustc_attr_parsing/src/context.rs

@@ -71,7 +71,7 @@ use crate::parser::{
 };
 use crate::session_diagnostics::{
     AttributeParseError, AttributeParseErrorReason, AttributeParseErrorSuggestions,
-    ParsedDescription,
+    ParsedDescription, UnusedDuplicate,
 };
 use crate::target_checking::AllowedTargets;
 use crate::{AttrSuggestionStyle, AttributeParser, AttributeTemplate, EmitAttribute};
@@ -436,11 +436,7 @@ impl<'f, 'sess: 'f> SharedContext<'f, 'sess> {
     pub(crate) fn warn_unused_duplicate(&mut self, used_span: Span, unused_span: Span) {
         self.emit_lint(
             rustc_session::lint::builtin::UNUSED_ATTRIBUTES,
-            rustc_errors::lints::UnusedDuplicate {
-                this: unused_span,
-                other: used_span,
-                warning: false,
-            },
+            UnusedDuplicate { this: unused_span, other: used_span, warning: false },
             unused_span,
         )
     }
@@ -452,11 +448,7 @@ impl<'f, 'sess: 'f> SharedContext<'f, 'sess> {
     ) {
         self.emit_lint(
             rustc_session::lint::builtin::UNUSED_ATTRIBUTES,
-            rustc_errors::lints::UnusedDuplicate {
-                this: unused_span,
-                other: used_span,
-                warning: true,
-            },
+            UnusedDuplicate { this: unused_span, other: used_span, warning: true },
             unused_span,
         )
     }

compiler/rustc_attr_parsing/src/session_diagnostics.rs

@@ -1045,3 +1045,16 @@ pub(crate) struct AdditionalCommaSuggestion {
     #[primary_span]
     pub span: Span,
 }
+
+#[derive(Diagnostic)]
+#[diag("unused attribute")]
+pub(crate) struct UnusedDuplicate {
+    #[suggestion("remove this attribute", code = "", applicability = "machine-applicable")]
+    pub this: Span,
+    #[note("attribute also specified here")]
+    pub other: Span,
+    #[warning(
+        "this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!"
+    )]
+    pub warning: bool,
+}

compiler/rustc_errors/src/lib.rs

@@ -79,7 +79,6 @@ mod diagnostic_impls;
 pub mod emitter;
 pub mod formatting;
 pub mod json;
-pub mod lints;
 mod lock;
 pub mod markdown;
 pub mod timings;