Warn useless deprecation in check_attr.

Author: cjgillot

compiler/rustc_hir/src/target.rs

@@ -51,7 +51,7 @@ pub enum Target {
     ForeignFn,
     ForeignStatic,
     ForeignTy,
-    GenericParam(GenericParamKind),
+    GenericParam { kind: GenericParamKind, has_default: bool },
     MacroDef,
     Param,
     PatField,
@@ -93,7 +93,7 @@ impl Target {
             | Target::ForeignFn
             | Target::ForeignStatic
             | Target::ForeignTy
-            | Target::GenericParam(_)
+            | Target::GenericParam { .. }
             | Target::MacroDef
             | Target::Param
             | Target::PatField
@@ -169,11 +169,17 @@ impl Target {
 
     pub fn from_generic_param(generic_param: &hir::GenericParam<'_>) -> Target {
         match generic_param.kind {
-            hir::GenericParamKind::Type { .. } => Target::GenericParam(GenericParamKind::Type),
+            hir::GenericParamKind::Type { default, .. } => Target::GenericParam {
+                kind: GenericParamKind::Type,
+                has_default: default.is_some(),
+            },
             hir::GenericParamKind::Lifetime { .. } => {
-                Target::GenericParam(GenericParamKind::Lifetime)
+                Target::GenericParam { kind: GenericParamKind::Lifetime, has_default: false }
             }
-            hir::GenericParamKind::Const { .. } => Target::GenericParam(GenericParamKind::Const),
+            hir::GenericParamKind::Const { default, .. } => Target::GenericParam {
+                kind: GenericParamKind::Const,
+                has_default: default.is_some(),
+            },
         }
     }
 
@@ -211,7 +217,7 @@ impl Target {
             Target::ForeignFn => "foreign function",
             Target::ForeignStatic => "foreign static item",
             Target::ForeignTy => "foreign type",
-            Target::GenericParam(kind) => match kind {
+            Target::GenericParam { kind, has_default: _ } => match kind {
                 GenericParamKind::Type => "type parameter",
                 GenericParamKind::Lifetime => "lifetime parameter",
                 GenericParamKind::Const => "const parameter",

compiler/rustc_passes/src/check_attr.rs

@@ -33,7 +33,7 @@ use rustc_session::config::CrateType;
 use rustc_session::lint;
 use rustc_session::lint::builtin::{
     CONFLICTING_REPR_HINTS, INVALID_DOC_ATTRIBUTES, INVALID_MACRO_EXPORT_ARGUMENTS,
-    UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES, UNUSED_ATTRIBUTES,
+    UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES, UNUSED_ATTRIBUTES, USELESS_DEPRECATED,
 };
 use rustc_session::parse::feature_err;
 use rustc_span::edition::Edition;
@@ -1001,7 +1001,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
             | Target::ForeignFn
             | Target::ForeignStatic
             | Target::ForeignTy
-            | Target::GenericParam(..)
+            | Target::GenericParam { .. }
             | Target::MacroDef
             | Target::PatField
             | Target::ExprField => None,
@@ -2264,6 +2264,28 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     errors::Deprecated,
                 );
             }
+            Target::Impl { of_trait: true }
+            | Target::GenericParam { has_default: false, kind: _ } => {
+                self.tcx.emit_node_span_lint(
+                    USELESS_DEPRECATED,
+                    hir_id,
+                    attr.span(),
+                    errors::DeprecatedAnnotationHasNoEffect { span: attr.span() },
+                );
+            }
+            Target::AssocConst | Target::Method(..) | Target::AssocTy
+                if matches!(
+                    self.tcx.def_kind(self.tcx.local_parent(hir_id.owner.def_id)),
+                    DefKind::Impl { of_trait: true }
+                ) =>
+            {
+                self.tcx.emit_node_span_lint(
+                    USELESS_DEPRECATED,
+                    hir_id,
+                    attr.span(),
+                    errors::DeprecatedAnnotationHasNoEffect { span: attr.span() },
+                );
+            }
             _ => {}
         }
     }

compiler/rustc_passes/src/stability.rs

@@ -27,9 +27,7 @@ use rustc_middle::query::Providers;
 use rustc_middle::ty::TyCtxt;
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_session::lint;
-use rustc_session::lint::builtin::{
-    DEPRECATED, INEFFECTIVE_UNSTABLE_TRAIT_IMPL, USELESS_DEPRECATED,
-};
+use rustc_session::lint::builtin::{DEPRECATED, INEFFECTIVE_UNSTABLE_TRAIT_IMPL};
 use rustc_span::{Span, Symbol, sym};
 use tracing::{debug, info};
 
@@ -125,19 +123,9 @@ impl<'a, 'tcx> Annotator<'a, 'tcx> {
         let const_stability_indirect = find_attr!(attrs, AttributeKind::ConstStabilityIndirect);
 
         let mut is_deprecated = false;
-        if let Some((depr, span)) = &depr {
+        if let Some((depr, _)) = &depr {
             is_deprecated = true;
 
-            if matches!(kind, AnnotationKind::Prohibited | AnnotationKind::DeprecationProhibited) {
-                let hir_id = self.tcx.local_def_id_to_hir_id(def_id);
-                self.tcx.emit_node_span_lint(
-                    USELESS_DEPRECATED,
-                    hir_id,
-                    *span,
-                    errors::DeprecatedAnnotationHasNoEffect { span: *span },
-                );
-            }
-
             // `Deprecation` is just two pointers, no need to intern it
             let depr_entry = DeprecationEntry::local(*depr, def_id);
             self.index.depr_map.insert(def_id, depr_entry);