From 7c6268ea2ef195f39faa4198d6713bae34beb93a Mon Sep 17 00:00:00 2001
From: Alex Rocha <alex.rocha@shopify.com>
Date: Tue, 3 Mar 2026 18:11:55 -0800
Subject: [PATCH] Index method aliases with RBS indexer

---
 rust/rubydex/src/indexing/rbs_indexer.rs | 71 +++++++++++++++++++++++-
 rust/rubydex/src/resolution.rs           | 33 +++++++++++
 2 files changed, 101 insertions(+), 3 deletions(-)

diff --git a/rust/rubydex/src/indexing/rbs_indexer.rs b/rust/rubydex/src/indexing/rbs_indexer.rs
index 08018fe5..8106c71d 100644
--- a/rust/rubydex/src/indexing/rbs_indexer.rs
+++ b/rust/rubydex/src/indexing/rbs_indexer.rs
@@ -1,8 +1,8 @@
 //! Visit the RBS AST and create type definitions.
 
 use ruby_rbs::node::{
-    self, ClassNode, CommentNode, ConstantNode, ExtendNode, GlobalNode, IncludeNode, ModuleNode, Node, NodeList,
-    PrependNode, TypeNameNode, Visit,
+    self, AliasKind, ClassNode, CommentNode, ConstantNode, ExtendNode, GlobalNode, IncludeNode, ModuleNode, Node,
+    NodeList, PrependNode, TypeNameNode, Visit,
 };
 
 use crate::diagnostic::Rule;
@@ -10,7 +10,7 @@ use crate::indexing::local_graph::LocalGraph;
 use crate::model::comment::Comment;
 use crate::model::definitions::{
     ClassDefinition, ConstantDefinition, Definition, DefinitionFlags, ExtendDefinition, GlobalVariableDefinition,
-    IncludeDefinition, Mixin, ModuleDefinition, PrependDefinition,
+    IncludeDefinition, MethodAliasDefinition, Mixin, ModuleDefinition, PrependDefinition,
 };
 use crate::model::document::Document;
 use crate::model::ids::{DefinitionId, NameId, ReferenceId, UriId};
@@ -324,6 +324,37 @@ impl Visit for RBSIndexer<'_> {
             Mixin::Extend(ExtendDefinition::new(ref_id))
         });
     }
+
+    fn visit_alias_node(&mut self, alias_node: &node::AliasNode) {
+        if alias_node.kind() != AliasKind::Instance {
+            return;
+        }
+
+        let lexical_nesting_id = self.parent_lexical_scope_id();
+
+        let mut new_name = Self::bytes_to_string(alias_node.new_name().name());
+        let mut old_name = Self::bytes_to_string(alias_node.old_name().name());
+        new_name.push_str("()");
+        old_name.push_str("()");
+
+        let new_name_str_id = self.local_graph.intern_string(new_name);
+        let old_name_str_id = self.local_graph.intern_string(old_name);
+
+        let offset = Offset::from_rbs_location(&alias_node.location());
+        let comments = Self::collect_comments(alias_node.comment());
+
+        let definition = Definition::MethodAlias(Box::new(MethodAliasDefinition::new(
+            new_name_str_id,
+            old_name_str_id,
+            self.uri_id,
+            offset,
+            comments,
+            Self::flags(&alias_node.annotations()),
+            lexical_nesting_id,
+        )));
+
+        self.register_definition(definition, lexical_nesting_id);
+    }
 }
 
 #[cfg(test)]
@@ -336,6 +367,7 @@ mod tests {
     use crate::{
         assert_def_comments_eq, assert_def_mixins_eq, assert_def_name_eq, assert_def_name_offset_eq, assert_def_str_eq,
         assert_def_superclass_ref_eq, assert_definition_at, assert_local_diagnostics_eq, assert_no_local_diagnostics,
+        assert_string_eq,
     };
 
     fn index_source(source: &str) -> LocalGraphTest {
@@ -714,4 +746,37 @@ mod tests {
             assert!(def.flags().contains(DefinitionFlags::DEPRECATED));
         });
     }
+
+    #[test]
+    fn index_alias_node() {
+        let context = index_source({
+            "
+            class Foo
+              # Some documentation
+              alias bar baz
+              alias qux quux
+              alias self.singleton_bar self.singleton_baz
+            end
+            "
+        });
+
+        assert_no_local_diagnostics!(&context);
+
+        // Singleton alias is ignored, so only class + 2 instance aliases
+        assert_eq!(context.graph().definitions().len(), 3);
+
+        assert_definition_at!(&context, "1:1-6:4", Class, |class_def| {
+            assert_definition_at!(&context, "3:3-3:16", MethodAlias, |def| {
+                assert_string_eq!(&context, def.new_name_str_id(), "bar()");
+                assert_string_eq!(&context, def.old_name_str_id(), "baz()");
+                assert_def_comments_eq!(&context, def, ["Some documentation\n"]);
+                assert_eq!(class_def.id(), def.lexical_nesting_id().unwrap());
+            });
+
+            assert_definition_at!(&context, "4:3-4:17", MethodAlias, |def| {
+                assert_string_eq!(&context, def.new_name_str_id(), "qux()");
+                assert_string_eq!(&context, def.old_name_str_id(), "quux()");
+            });
+        });
+    }
 }
diff --git a/rust/rubydex/src/resolution.rs b/rust/rubydex/src/resolution.rs
index 0a7648c7..88ffc0b2 100644
--- a/rust/rubydex/src/resolution.rs
+++ b/rust/rubydex/src/resolution.rs
@@ -4967,4 +4967,37 @@ mod tests {
         assert_declaration_exists!(context, "Baz");
         assert_constant_reference_to!(context, "CONST", "file:///reopen.rb:5:5-5:10");
     }
+
+    #[test]
+    fn rbs_method_alias_resolution() {
+        let mut context = GraphTest::new();
+        context.index_uri("file:///foo.rb", {
+            r"
+            class Foo
+              def bar; end
+            end
+
+            module Baz
+              def original; end
+            end
+            "
+        });
+        context.index_rbs_uri("file:///test.rbs", {
+            r"
+            class Foo
+              alias qux bar
+            end
+
+            module Baz
+              alias copy original
+            end
+            "
+        });
+        context.resolve();
+
+        assert_no_diagnostics!(&context);
+
+        assert_members_eq!(context, "Foo", ["bar()", "qux()"]);
+        assert_members_eq!(context, "Baz", ["copy()", "original()"]);
+    }
 }