Move diagnostic::do_not_recommend target checking

compiler/rustc_attr_parsing/src/attributes/diagnostic/do_not_recommend.rs

@@ -1,11 +1,16 @@
+use rustc_errors::Diagnostic;
 use rustc_feature::{AttributeTemplate, template};
+use rustc_hir::Target;
 use rustc_hir::attrs::AttributeKind;
 use rustc_hir::lints::AttributeLintKind;
-use rustc_session::lint::builtin::MALFORMED_DIAGNOSTIC_ATTRIBUTES;
+use rustc_session::lint::builtin::{
+    MALFORMED_DIAGNOSTIC_ATTRIBUTES, MISPLACED_DIAGNOSTIC_ATTRIBUTES,
+};
 use rustc_span::{Symbol, sym};
 
 use crate::attributes::{OnDuplicate, SingleAttributeParser};
 use crate::context::{AcceptContext, Stage};
+use crate::errors::IncorrectDoNotRecommendLocation;
 use crate::parser::ArgParser;
 use crate::target_checking::{ALL_TARGETS, AllowedTargets};
 
@@ -13,7 +18,8 @@
 impl<S: Stage> SingleAttributeParser<S> for DoNotRecommendParser {
     const PATH: &[Symbol] = &[sym::diagnostic, sym::do_not_recommend];
     const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Warn;
-    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(ALL_TARGETS); // Checked in check_attr.
+    // "Allowed" on any target, noop on all but trait impls
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(ALL_TARGETS);
     const TEMPLATE: AttributeTemplate = template!(Word /*doesn't matter */);
 
     fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser) -> Option<AttributeKind> {
@@ -25,6 +31,16 @@ fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser) -> Option<Attrib
                 attr_span,
             );
         }
+
+        if !matches!(cx.target, Target::Impl { of_trait: true }) {
+            cx.emit_dyn_lint(
+                MISPLACED_DIAGNOSTIC_ATTRIBUTES,
+                move |dcx, level| IncorrectDoNotRecommendLocation.into_diag(dcx, level),
+                attr_span,
+            );
+            return None;
+        }
+
         Some(AttributeKind::DoNotRecommend { attr_span })
     }
 }

compiler/rustc_attr_parsing/src/errors.rs

@@ -274,3 +274,7 @@ pub(crate) struct DiagnosticOnUnknownOnlyForImports {
     #[label("not an import")]
     pub target_span: Span,
 }
+
+#[derive(Diagnostic)]
+#[diag("`#[diagnostic::do_not_recommend]` can only be placed on trait implementations")]
+pub(crate) struct IncorrectDoNotRecommendLocation;

compiler/rustc_passes/src/check_attr.rs

@@ -199,7 +199,6 @@ fn check_attributes(
                 Attribute::Parsed(AttributeKind::RustcMustImplementOneOf { attr_span, fn_names }) => {
                     self.check_rustc_must_implement_one_of(*attr_span, fn_names, hir_id,target)
                 },
-                Attribute::Parsed(AttributeKind::DoNotRecommend{attr_span}) => {self.check_do_not_recommend(*attr_span, hir_id, target, item)},
                 Attribute::Parsed(AttributeKind::OnUnimplemented{directive,..}) => {self.check_diagnostic_on_unimplemented(hir_id, directive.as_deref())},
                 Attribute::Parsed(AttributeKind::OnConst{span, ..}) => {self.check_diagnostic_on_const(*span, hir_id, target, item)}
                 Attribute::Parsed(AttributeKind::OnMove { directive , .. }) => {
@@ -222,6 +221,7 @@ fn check_attributes(
                     | AttributeKind::CustomMir(..)
                     | AttributeKind::DebuggerVisualizer(..)
                     | AttributeKind::DefaultLibAllocator
+                    | AttributeKind::DoNotRecommend {..}
                     // `#[doc]` is actually a lot more than just doc comments, so is checked below
                     | AttributeKind::DocComment {..}
                     | AttributeKind::EiiDeclaration { .. }
@@ -490,30 +490,6 @@ fn check_eii_impl(&self, impls: &[EiiImpl], target: Target) {
         }
     }
 
-    /// Checks if `#[diagnostic::do_not_recommend]` is applied on a trait impl
-    fn check_do_not_recommend(
-        &self,
-        attr_span: Span,
-        hir_id: HirId,
-        target: Target,
-        item: Option<ItemLike<'_>>,
-    ) {
-        if !matches!(target, Target::Impl { .. })
-            || matches!(
-                item,
-                Some(ItemLike::Item(hir::Item {  kind: hir::ItemKind::Impl(_impl),.. }))
-                    if _impl.of_trait.is_none()
-            )
-        {
-            self.tcx.emit_node_span_lint(
-                MISPLACED_DIAGNOSTIC_ATTRIBUTES,
-                hir_id,
-                attr_span,
-                errors::IncorrectDoNotRecommendLocation,
-            );
-        }
-    }
-
     /// Checks use of generic formatting parameters in `#[diagnostic::on_unimplemented]`
     fn check_diagnostic_on_unimplemented(&self, hir_id: HirId, directive: Option<&Directive>) {
         if let Some(directive) = directive {

compiler/rustc_passes/src/errors.rs

@@ -13,10 +13,6 @@
 use crate::check_attr::ProcMacroKind;
 use crate::lang_items::Duplicate;
 
-#[derive(Diagnostic)]
-#[diag("`#[diagnostic::do_not_recommend]` can only be placed on trait implementations")]
-pub(crate) struct IncorrectDoNotRecommendLocation;
-
 #[derive(Diagnostic)]
 #[diag("`#[loop_match]` should be applied to a loop")]
 pub(crate) struct LoopMatchAttr {