[RFC 2397] Deny incorrect locations

2 files changed, 18 insertions, 0 deletions

diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index c59c06ac31e..f9f9799d3e4 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -82,6 +82,7 @@ impl CheckAttrVisitor<'_> {
         let attrs = self.tcx.hir().attrs(hir_id);
         for attr in attrs {
             let attr_is_valid = match attr.name_or_empty() {
+                sym::do_not_recommend => self.check_do_not_recommend(attr.span, target),
                 sym::inline => self.check_inline(hir_id, attr, span, target),
                 sym::no_coverage => self.check_no_coverage(hir_id, attr, span, target),
                 sym::non_exhaustive => self.check_non_exhaustive(hir_id, attr, span, target),
@@ -241,6 +242,16 @@ impl CheckAttrVisitor<'_> {
         );
     }
 
+    /// Checks if `#[do_not_recommend]` is applied on a trait impl.
+    fn check_do_not_recommend(&self, attr_span: Span, target: Target) -> bool {
+        if let Target::Impl = target {
+            true
+        } else {
+            self.tcx.sess.emit_err(errors::IncorrectDoNotRecommendLocation { span: attr_span });
+            false
+        }
+    }
+
     /// Checks if an `#[inline]` is applied to a function or a closure. Returns `true` if valid.
     fn check_inline(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) -> bool {
         match target {
diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index c6cd69add28..9c6519ea4bb 100644
--- a/compiler/rustc_passes/src/errors.rs
+++ b/compiler/rustc_passes/src/errors.rs
@@ -14,6 +14,13 @@ use rustc_span::{Span, Symbol, DUMMY_SP};
 
 use crate::lang_items::Duplicate;
 
+#[derive(Diagnostic)]
+#[diag(passes_incorrect_do_not_recommend_location)]
+pub struct IncorrectDoNotRecommendLocation {
+    #[primary_span]
+    pub span: Span,
+}
+
 #[derive(LintDiagnostic)]
 #[diag(passes_outer_crate_level_attr)]
 pub struct OuterCrateLevelAttr;