attributes: Add class for sharing methods on attributes.

gcc/rust/ChangeLog:

	* util/rust-attributes.h (class Attributes): New.
	* util/rust-attributes.cc: Implement Attributes::is_known().
	* ast/rust-collect-lang-items.cc (is_known_attribute): Remove.
	(get_lang_item_attr): Call Attributes::is_known() instead.
	* hir/rust-ast-lower-base.cc (ASTLoweringBase::handle_outer_attributes): Likewise.
	(ASTLoweringBase::is_known_attribute): Remove.

gcc/rust/ast/rust-collect-lang-items.cc

@@ -27,25 +27,14 @@
 namespace Rust {
 namespace AST {
 
-// FIXME: Before merging: De-duplicate with function in rust-ast-lower-base.cc
-bool
-is_known_attribute (const std::string &attribute_path)
-{
-  const auto &lookup
-    = Analysis::BuiltinAttributeMappings::get ()->lookup_builtin (
-      attribute_path);
-
-  return !lookup.is_error ();
-}
-
 template <typename T>
 tl::optional<LangItem::Kind>
 get_lang_item_attr (const T &maybe_lang_item)
 {
   for (const auto &attr : maybe_lang_item.get_outer_attrs ())
     {
       const auto &str_path = attr.get_path ().as_string ();
-      if (!is_known_attribute (str_path))
+      if (!Analysis::Attributes::is_known (str_path))
 	{
 	  rust_error_at (attr.get_locus (), "unknown attribute");
 	  continue;

gcc/rust/hir/rust-ast-lower-base.cc

@@ -25,6 +25,7 @@
 #include "rust-diagnostics.h"
 #include "rust-item.h"
 #include "rust-system.h"
+#include "rust-attributes.h"
 
 namespace Rust {
 namespace HIR {
@@ -751,7 +752,7 @@ ASTLoweringBase::handle_outer_attributes (const ItemWrapper &item)
   for (const auto &attr : item.get_outer_attrs ())
     {
       const auto &str_path = attr.get_path ().as_string ();
-      if (!is_known_attribute (str_path))
+      if (!Analysis::Attributes::is_known (str_path))
 	{
 	  rust_error_at (attr.get_locus (), "unknown attribute");
 	  continue;
@@ -814,13 +815,6 @@ ASTLoweringBase::handle_lang_item_attribute (const ItemWrapper &item,
     rust_error_at (attr.get_locus (), "unknown lang item");
 }
 
-bool
-ASTLoweringBase::is_known_attribute (const std::string &attribute_path) const
-{
-  const auto &lookup = attr_mappings->lookup_builtin (attribute_path);
-  return !lookup.is_error ();
-}
-
 bool
 ASTLoweringBase::attribute_handled_in_another_pass (
   const std::string &attribute_path) const

gcc/rust/util/rust-attributes.cc

@@ -29,6 +29,15 @@
 namespace Rust {
 namespace Analysis {
 
+bool
+Attributes::is_known (const std::string &attribute_path)
+{
+  const auto &lookup
+    = BuiltinAttributeMappings::get ()->lookup_builtin (attribute_path);
+
+  return !lookup.is_error ();
+}
+
 using Attrs = Values::Attributes;
 
 // https://doc.rust-lang.org/stable/nightly-rustc/src/rustc_feature/builtin_attrs.rs.html#248

gcc/rust/util/rust-attributes.h

@@ -25,6 +25,12 @@
 namespace Rust {
 namespace Analysis {
 
+class Attributes
+{
+public:
+  static bool is_known (const std::string &attribute_path);
+};
+
 enum CompilerPass
 {
   UNKNOWN,