Stop using the old validate_attr logic for stability attributes

compiler/rustc_attr_parsing/src/attributes/stability.rs

@@ -74,8 +74,15 @@ impl<S: Stage> AttributeParser<S> for StabilityParser {
             template!(NameValueStr: "deprecation message"),
             |this, cx, args| {
                 reject_outside_std!(cx);
-                this.allowed_through_unstable_modules =
-                    args.name_value().and_then(|i| i.value_as_str())
+                let Some(nv) = args.name_value() else {
+                    cx.expected_name_value(cx.attr_span, None);
+                    return;
+                };
+                let Some(value_str) = nv.value_as_str() else {
+                    cx.expected_string_literal(nv.value_span, Some(nv.value_as_lit()));
+                    return;
+                };
+                this.allowed_through_unstable_modules = Some(value_str);
             },
         ),
     ];
@@ -247,7 +254,12 @@ pub(crate) fn parse_stability<S: Stage>(
     let mut feature = None;
     let mut since = None;
 
-    for param in args.list()?.mixed() {
+    let ArgParser::List(list) = args else {
+        cx.expected_list(cx.attr_span);
+        return None;
+    };
+
+    for param in list.mixed() {
         let param_span = param.span();
         let Some(param) = param.meta_item() else {
             cx.emit_err(session_diagnostics::UnsupportedLiteral {
@@ -322,7 +334,13 @@ pub(crate) fn parse_unstability<S: Stage>(
     let mut is_soft = false;
     let mut implied_by = None;
     let mut old_name = None;
-    for param in args.list()?.mixed() {
+
+    let ArgParser::List(list) = args else {
+        cx.expected_list(cx.attr_span);
+        return None;
+    };
+
+    for param in list.mixed() {
         let Some(param) = param.meta_item() else {
             cx.emit_err(session_diagnostics::UnsupportedLiteral {
                 span: param.span(),

compiler/rustc_parse/src/validate_attr.rs

@@ -285,6 +285,9 @@ pub fn check_builtin_meta_item(
                 | sym::rustc_do_not_implement_via_object
                 | sym::rustc_coinductive
                 | sym::const_trait
+                | sym::stable
+                | sym::unstable
+                | sym::rustc_allowed_through_unstable_modules
                 | sym::rustc_specialization_trait
                 | sym::rustc_unsafe_specialization_marker
                 | sym::rustc_allow_incoherent_impl

tests/ui/stability-attribute/stability-attribute-sanity-4.stderr

@@ -1,26 +1,38 @@
-error: malformed `unstable` attribute input
+error[E0539]: malformed `unstable` attribute input
   --> $DIR/stability-attribute-sanity-4.rs:8:5
    |
 LL |     #[unstable]
-   |     ^^^^^^^^^^^ help: must be of the form: `#[unstable(feature = "name", reason = "...", issue = "N")]`
+   |     ^^^^^^^^^^^
+   |     |
+   |     expected this to be a list
+   |     help: must be of the form: `#[unstable(feature = "name", reason = "...", issue = "N")]`
 
-error: malformed `unstable` attribute input
+error[E0539]: malformed `unstable` attribute input
   --> $DIR/stability-attribute-sanity-4.rs:11:5
    |
 LL |     #[unstable = "b"]
-   |     ^^^^^^^^^^^^^^^^^ help: must be of the form: `#[unstable(feature = "name", reason = "...", issue = "N")]`
+   |     ^^^^^^^^^^^^^^^^^
+   |     |
+   |     expected this to be a list
+   |     help: must be of the form: `#[unstable(feature = "name", reason = "...", issue = "N")]`
 
-error: malformed `stable` attribute input
+error[E0539]: malformed `stable` attribute input
   --> $DIR/stability-attribute-sanity-4.rs:14:5
    |
 LL |     #[stable]
-   |     ^^^^^^^^^ help: must be of the form: `#[stable(feature = "name", since = "version")]`
+   |     ^^^^^^^^^
+   |     |
+   |     expected this to be a list
+   |     help: must be of the form: `#[stable(feature = "name", since = "version")]`
 
-error: malformed `stable` attribute input
+error[E0539]: malformed `stable` attribute input
   --> $DIR/stability-attribute-sanity-4.rs:17:5
    |
 LL |     #[stable = "a"]
-   |     ^^^^^^^^^^^^^^^ help: must be of the form: `#[stable(feature = "name", since = "version")]`
+   |     ^^^^^^^^^^^^^^^
+   |     |
+   |     expected this to be a list
+   |     help: must be of the form: `#[stable(feature = "name", since = "version")]`
 
 error[E0542]: missing 'since'
   --> $DIR/stability-attribute-sanity-4.rs:21:5
@@ -42,5 +54,5 @@ LL |     #[deprecated = "a"]
 
 error: aborting due to 7 previous errors
 
-Some errors have detailed explanations: E0542, E0543.
-For more information about an error, try `rustc --explain E0542`.
+Some errors have detailed explanations: E0539, E0542, E0543.
+For more information about an error, try `rustc --explain E0539`.