Recover non-list repr attr with a span for later attr validation

Author: compiler-errors

compiler/rustc_attr_parsing/src/attributes/repr.rs

@@ -32,13 +32,14 @@ impl<S: Stage> CombineAttributeParser<S> for ReprParser {
         cx: &'c mut AcceptContext<'_, '_, S>,
         args: &'c ArgParser<'_>,
     ) -> impl IntoIterator<Item = Self::Item> + 'c {
-        let mut reprs = Vec::new();
-
         let Some(list) = args.list() else {
             cx.expected_list(cx.attr_span);
-            return reprs;
+            // Recover this as `ReprEmpty` so that we have a span to point to.
+            // This span is used for, e.g., complaining about crate-level `#![repr]`.
+            return vec![(ReprAttr::ReprEmpty, cx.attr_span)];
         };
 
+        let mut reprs = Vec::new();
         if list.is_empty() {
             // this is so validation can emit a lint
             reprs.push((ReprAttr::ReprEmpty, cx.attr_span));

compiler/rustc_passes/src/check_attr.rs

@@ -2052,12 +2052,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     if item.is_some() {
                         match target {
                             Target::Struct | Target::Union | Target::Enum => continue,
-                            Target::Fn | Target::Method(_) => {
-                                self.dcx().emit_err(errors::ReprAlignShouldBeAlign {
-                                    span: *repr_span,
-                                    item: target.name(),
-                                });
-                            }
                             _ => {
                                 self.dcx().emit_err(errors::AttrApplication::StructEnumUnion {
                                     hint_span: *repr_span,

tests/ui/attributes/malformed-attrs.rs

@@ -29,6 +29,10 @@
 #![windows_subsystem]
 //~^ ERROR malformed
 
+#![repr]
+//~^ ERROR malformed
+//~| ERROR `repr` attribute cannot be used at crate level
+
 #[unsafe(export_name)]
 //~^ ERROR malformed
 #[rustc_allow_const_fn_unstable]
@@ -47,6 +51,7 @@
 //~^ ERROR malformed
 #[repr]
 //~^ ERROR malformed
+//~| ERROR attribute should be applied to a struct, enum, or union
 #[rustc_as_ptr = 5]
 //~^ ERROR malformed
 #[inline = 5]