Rollup merge of #140372 - mejrs:attrs, r=jdonszelmann

Exhaustively handle parsed attributes in CheckAttr

This pr
 - Deletes the unused `DiagnosticAttribute ` struct and variant
 - Comments the `AttributeKind ` enum
 - The match in `CheckAttrVisitor` is now exhaustive for `AttributeKind::Parsed`.
 - Moved some checks around after that change

I did *not* thoroughly check that there's no duplicated logic between this pass and the attribute parsing but I think it's OK.

  r? ````@jdonszelmann````

compiler/rustc_attr_data_structures/src/attributes.rs

@@ -57,14 +57,6 @@ impl OptimizeAttr {
     }
 }
 
-#[derive(Clone, Debug, Encodable, Decodable, HashStable_Generic, PrintAttribute)]
-pub enum DiagnosticAttribute {
-    // tidy-alphabetical-start
-    DoNotRecommend,
-    OnUnimplemented,
-    // tidy-alphabetical-end
-}
-
 #[derive(PartialEq, Debug, Encodable, Decodable, Copy, Clone, HashStable_Generic, PrintAttribute)]
 pub enum ReprAttr {
     ReprInt(IntType),
@@ -160,40 +152,52 @@ impl Deprecation {
 #[derive(Clone, Debug, HashStable_Generic, Encodable, Decodable, PrintAttribute)]
 pub enum AttributeKind {
     // tidy-alphabetical-start
+    /// Represents `#[rustc_allow_const_fn_unstable]`.
     AllowConstFnUnstable(ThinVec<Symbol>),
+
+    /// Represents `#[allow_internal_unstable]`.
     AllowInternalUnstable(ThinVec<(Symbol, Span)>),
+
+    /// Represents `#[rustc_default_body_unstable]`.
     BodyStability {
         stability: DefaultBodyStability,
         /// Span of the `#[rustc_default_body_unstable(...)]` attribute
         span: Span,
     },
+
+    /// Represents `#[rustc_confusables]`.
     Confusables {
         symbols: ThinVec<Symbol>,
         // FIXME(jdonszelmann): remove when target validation code is moved
         first_span: Span,
     },
+
+    /// Represents `#[rustc_const_stable]` and `#[rustc_const_unstable]`.
     ConstStability {
         stability: PartialConstStability,
         /// Span of the `#[rustc_const_stable(...)]` or `#[rustc_const_unstable(...)]` attribute
         span: Span,
     },
+
+    /// Represents `#[rustc_const_stable_indirect]`.
     ConstStabilityIndirect,
-    Deprecation {
+
-        deprecation: Deprecation,
+    /// Represents [`#[deprecated]`](https://doc.rust-lang.org/stable/reference/attributes/diagnostics.html#the-deprecated-attribute).
-        span: Span,
+    Deprecation { deprecation: Deprecation, span: Span },
-    },
+
-    Diagnostic(DiagnosticAttribute),
+    /// Represents [`#[doc]`](https://doc.rust-lang.org/stable/rustdoc/write-documentation/the-doc-attribute.html).
-    DocComment {
+    DocComment { style: AttrStyle, kind: CommentKind, span: Span, comment: Symbol },
-        style: AttrStyle,
+
-        kind: CommentKind,
+    /// Represents `#[rustc_macro_transparency]`.
-        span: Span,
-        comment: Symbol,
-    },
     MacroTransparency(Transparency),
+
+    /// Represents [`#[repr]`](https://doc.rust-lang.org/stable/reference/type-layout.html#representations).
     Repr(ThinVec<(ReprAttr, Span)>),
+
+    /// Represents `#[stable]`, `#[unstable]` and `#[rustc_allowed_through_unstable_modules]`.
     Stability {
         stability: Stability,
-        /// Span of the `#[stable(...)]` or `#[unstable(...)]` attribute
+        /// Span of the attribute.
         span: Span,
     },
     // tidy-alphabetical-end

compiler/rustc_passes/src/check_attr.rs

@@ -132,7 +132,22 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                         target,
                         attrs,
                     ),
-                _ => {
+                Attribute::Parsed(AttributeKind::AllowConstFnUnstable { .. }) => {
+                    self.check_rustc_allow_const_fn_unstable(hir_id, attr, span, target)
+                }
+                Attribute::Parsed(AttributeKind::Deprecation { .. }) => {
+                    self.check_deprecated(hir_id, attr, span, target)
+                }
+                Attribute::Parsed(AttributeKind::DocComment { .. }) => { /* `#[doc]` is actually a lot more than just doc comments, so is checked below*/
+                }
+                Attribute::Parsed(AttributeKind::Repr(_)) => { /* handled below this loop and elsewhere */
+                }
+                Attribute::Parsed(
+                    AttributeKind::BodyStability { .. }
+                    | AttributeKind::ConstStabilityIndirect
+                    | AttributeKind::MacroTransparency(_),
+                ) => { /* do nothing  */ }
+                Attribute::Unparsed(_) => {
                     match attr.path().as_slice() {
                         [sym::diagnostic, sym::do_not_recommend, ..] => {
                             self.check_do_not_recommend(attr.span(), hir_id, target, attr, item)
@@ -169,9 +184,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                             self.check_rustc_layout_scalar_valid_range(attr, span, target)
                         }
                         [sym::debugger_visualizer, ..] => self.check_debugger_visualizer(attr, target),
-                        [sym::rustc_allow_const_fn_unstable, ..] => {
-                            self.check_rustc_allow_const_fn_unstable(hir_id, attr, span, target)
-                        }
                         [sym::rustc_std_internal_symbol, ..] => {
                             self.check_rustc_std_internal_symbol(attr, span, target)
                         }
@@ -229,7 +241,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                         [sym::link_name, ..] => self.check_link_name(hir_id, attr, span, target),
                         [sym::link_section, ..] => self.check_link_section(hir_id, attr, span, target),
                         [sym::no_mangle, ..] => self.check_no_mangle(hir_id, attr, span, target),
-                        [sym::deprecated, ..] => self.check_deprecated(hir_id, attr, span, target),
                         [sym::macro_use, ..] | [sym::macro_escape, ..] => {
                             self.check_macro_use(hir_id, attr, target)
                         }
@@ -283,7 +294,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                             | sym::pointee // FIXME(derive_coerce_pointee)
                             | sym::omit_gdb_pretty_printer_section // FIXME(omit_gdb_pretty_printer_section)
                             | sym::used // handled elsewhere to restrict to static items
-                            | sym::repr // handled elsewhere to restrict to type decls items
                             | sym::instruction_set // broken on stable!!!
                             | sym::windows_subsystem // broken on stable!!!
                             | sym::patchable_function_entry // FIXME(patchable_function_entry)