Check #[diagnostic::do_not_recommend] for arguments

This commit adds a check that verifies that no arguments are passed to
`#[diagnostic::do_not_recommend]`. If we detect arguments we emit a warning.

compiler/rustc_passes/messages.ftl

@@ -357,6 +357,9 @@ passes_ignored_derived_impls =
 passes_implied_feature_not_exist =
     feature `{$implied_by}` implying `{$feature}` does not exist
 
+passes_incorrect_do_not_recommend_args =
+    `#[diagnostic::do_not_recommend]` does not expect any arguments
+
 passes_incorrect_do_not_recommend_location =
     `#[diagnostic::do_not_recommend]` can only be placed on trait implementations
 

compiler/rustc_passes/src/check_attr.rs

@@ -115,7 +115,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         for attr in attrs {
             match attr.path().as_slice() {
                 [sym::diagnostic, sym::do_not_recommend, ..] => {
-                    self.check_do_not_recommend(attr.span, hir_id, target)
+                    self.check_do_not_recommend(attr.span, hir_id, target, attr)
                 }
                 [sym::diagnostic, sym::on_unimplemented, ..] => {
                     self.check_diagnostic_on_unimplemented(attr.span, hir_id, target)
@@ -348,7 +348,13 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
     }
 
     /// 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) {
+    fn check_do_not_recommend(
+        &self,
+        attr_span: Span,
+        hir_id: HirId,
+        target: Target,
+        attr: &Attribute,
+    ) {
         if !matches!(target, Target::Impl) {
             self.tcx.emit_node_span_lint(
                 UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES,
@@ -357,6 +363,14 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 errors::IncorrectDoNotRecommendLocation,
             );
         }
+        if !attr.is_word() {
+            self.tcx.emit_node_span_lint(
+                UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES,
+                hir_id,
+                attr_span,
+                errors::DoNotRecommendDoesNotExpectArgs,
+            );
+        }
     }
 
     /// Checks if `#[diagnostic::on_unimplemented]` is applied to a trait definition

compiler/rustc_passes/src/errors.rs

@@ -20,6 +20,10 @@ use crate::lang_items::Duplicate;
 #[diag(passes_incorrect_do_not_recommend_location)]
 pub(crate) struct IncorrectDoNotRecommendLocation;
 
+#[derive(LintDiagnostic)]
+#[diag(passes_incorrect_do_not_recommend_args)]
+pub(crate) struct DoNotRecommendDoesNotExpectArgs;
+
 #[derive(Diagnostic)]
 #[diag(passes_autodiff_attr)]
 pub(crate) struct AutoDiffAttr {

tests/ui/diagnostic_namespace/do_not_recommend/does_not_acccept_args.current.stderr

@@ -0,0 +1,22 @@
+warning: `#[diagnostic::do_not_recommend]` does not expect any arguments
+  --> $DIR/does_not_acccept_args.rs:12:1
+   |
+LL | #[diagnostic::do_not_recommend(not_accepted)]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(unknown_or_malformed_diagnostic_attributes)]` on by default
+
+warning: `#[diagnostic::do_not_recommend]` does not expect any arguments
+  --> $DIR/does_not_acccept_args.rs:16:1
+   |
+LL | #[diagnostic::do_not_recommend(not_accepted = "foo")]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+warning: `#[diagnostic::do_not_recommend]` does not expect any arguments
+  --> $DIR/does_not_acccept_args.rs:20:1
+   |
+LL | #[diagnostic::do_not_recommend(not_accepted(42))]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+warning: 3 warnings emitted
+

tests/ui/diagnostic_namespace/do_not_recommend/does_not_acccept_args.next.stderr

@@ -0,0 +1,22 @@
+warning: `#[diagnostic::do_not_recommend]` does not expect any arguments
+  --> $DIR/does_not_acccept_args.rs:12:1
+   |
+LL | #[diagnostic::do_not_recommend(not_accepted)]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(unknown_or_malformed_diagnostic_attributes)]` on by default
+
+warning: `#[diagnostic::do_not_recommend]` does not expect any arguments
+  --> $DIR/does_not_acccept_args.rs:16:1
+   |
+LL | #[diagnostic::do_not_recommend(not_accepted = "foo")]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+warning: `#[diagnostic::do_not_recommend]` does not expect any arguments
+  --> $DIR/does_not_acccept_args.rs:20:1
+   |
+LL | #[diagnostic::do_not_recommend(not_accepted(42))]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+warning: 3 warnings emitted
+

tests/ui/diagnostic_namespace/do_not_recommend/does_not_acccept_args.rs

@@ -0,0 +1,24 @@
+//@ check-pass
+//@ revisions: current next
+//@ ignore-compare-mode-next-solver (explicit revisions)
+//@[next] compile-flags: -Znext-solver
+
+#![feature(do_not_recommend)]
+
+trait Foo {}
+trait Bar {}
+trait Baz {}
+
+#[diagnostic::do_not_recommend(not_accepted)]
+//~^ WARNING `#[diagnostic::do_not_recommend]` does not expect any arguments
+impl<T> Foo for T where T: Send {}
+
+#[diagnostic::do_not_recommend(not_accepted = "foo")]
+//~^ WARNING `#[diagnostic::do_not_recommend]` does not expect any arguments
+impl<T> Bar for T where T: Send {}
+
+#[diagnostic::do_not_recommend(not_accepted(42))]
+//~^ WARNING `#[diagnostic::do_not_recommend]` does not expect any arguments
+impl<T> Baz for T where T: Send {}
+
+fn main() {}