Rewrite check_invalid_where_predicate_attrs

Author: JonathanBrouwer

compiler/rustc_attr_parsing/src/target_checking.rs

@@ -292,15 +292,16 @@ impl<'sess, S: Stage> AttributeParser<'sess, S> {
         // in where clauses. After that, this function would become useless.
         let spans = attrs
             .into_iter()
-            // FIXME: We shouldn't need to special-case `doc`!
-            .filter(|attr| {
-                matches!(
-                    attr,
-                    Attribute::Parsed(AttributeKind::DocComment { .. } | AttributeKind::Doc(_))
-                        | Attribute::Unparsed(_)
-                )
+            .filter_map(|attr| {
+                match attr {
+                    Attribute::Parsed(AttributeKind::DocComment { span, .. }) => Some(*span),
+                    // FIXME: We shouldn't need to special-case `doc`!
+                    Attribute::Parsed(AttributeKind::Doc(attr)) => Some(attr.first_span),
+                    // Checked during attribute parsing target checking
+                    Attribute::Parsed(_) => None,
+                    Attribute::Unparsed(attr) => Some(attr.span),
+                }
             })
-            .map(|attr| attr.span())
             .collect::<Vec<_>>();
         if !spans.is_empty() {
             self.dcx()

tests/ui/attributes/where-doc.rs

@@ -0,0 +1,34 @@
+#![feature(where_clause_attrs)]
+#![allow(invalid_doc_attributes)]
+
+fn test()
+where
+#[doc(alias = ":(")]
+//~^ ERROR most attributes are not supported in `where` clauses
+//~| ERROR `#[doc(alias = "...")]` isn't allowed on where predicate
+():,
+
+#[doc(hidden)]
+//~^ ERROR most attributes are not supported in `where` clauses
+():,
+
+#[doc = ""]
+//~^ ERROR most attributes are not supported in `where` clauses
+():,
+
+// == That the doc attributes below don't trigger the error is a bug
+#[doc()]
+():,
+
+#[doc(5)]
+():,
+
+#[doc]
+():,
+
+#[doc = 5]
+():,
+
+{ }
+
+fn main() {}

tests/ui/attributes/where-doc.stderr

@@ -0,0 +1,32 @@
+error: most attributes are not supported in `where` clauses
+  --> $DIR/where-doc.rs:6:1
+   |
+LL | #[doc(alias = ":(")]
+   | ^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: only `#[cfg]` and `#[cfg_attr]` are supported
+
+error: most attributes are not supported in `where` clauses
+  --> $DIR/where-doc.rs:11:1
+   |
+LL | #[doc(hidden)]
+   | ^^^^^^^^^^^^^^
+   |
+   = help: only `#[cfg]` and `#[cfg_attr]` are supported
+
+error: most attributes are not supported in `where` clauses
+  --> $DIR/where-doc.rs:15:1
+   |
+LL | #[doc = ""]
+   | ^^^^^^^^^^^
+   |
+   = help: only `#[cfg]` and `#[cfg_attr]` are supported
+
+error: `#[doc(alias = "...")]` isn't allowed on where predicate
+  --> $DIR/where-doc.rs:6:15
+   |
+LL | #[doc(alias = ":(")]
+   |               ^^^^
+
+error: aborting due to 4 previous errors
+