From 6fe0014219039bd5624afdb9623a40471d771a1e Mon Sep 17 00:00:00 2001
From: Lewis Russell <lewis6991@gmail.com>
Date: Fri, 6 Feb 2026 20:32:03 +0000
Subject: [PATCH] fix(typecheck): prefer declared globals for index member
 ownership

When setting a member owner for an index expression with a name prefix
(e.g. `table.unpack`), prefer the declared global type cache over the
inferred prefix type. This keeps stdlib members attached to their type
defs and avoids losing them after casts (like `---@cast table unknown`).

Skip the override when the name is shadowed by a local.
---
 .../src/compilation/analyzer/lua/stats.rs     | 38 +++++++++++++++++++
 .../src/semantic/type_check/test.rs           | 25 +++++++++++-
 2 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/crates/emmylua_code_analysis/src/compilation/analyzer/lua/stats.rs b/crates/emmylua_code_analysis/src/compilation/analyzer/lua/stats.rs
index 02aabe390..5cc87dd6a 100644
--- a/crates/emmylua_code_analysis/src/compilation/analyzer/lua/stats.rs
+++ b/crates/emmylua_code_analysis/src/compilation/analyzer/lua/stats.rs
@@ -207,6 +207,44 @@ fn set_index_expr_owner(analyzer: &mut LuaAnalyzer, var_expr: LuaVarExpr) -> Opt
 
     match analyzer.infer_expr(&prefix_expr.clone()) {
         Ok(prefix_type) => {
+            // Prefer declared global types for name prefixes when choosing a member owner.
+            // This keeps stdlib members (like table.unpack) attached to their type defs.
+            let prefix_type = if let LuaExpr::NameExpr(name_expr) = &prefix_expr {
+                let mut explicit_type = None;
+                if let Some(name) = name_expr.get_name_text() {
+                    // Avoid attaching members to stdlib globals when a local shadows the name.
+                    let is_shadowed = analyzer
+                        .db
+                        .get_decl_index()
+                        .get_decl_tree(&file_id)
+                        .and_then(|tree| tree.find_local_decl(&name, name_expr.get_position()))
+                        .map(|decl| decl.is_local() || decl.is_implicit_self())
+                        .unwrap_or(false);
+                    if !is_shadowed
+                        && let Some(decl_ids) =
+                            analyzer.db.get_global_index().get_global_decl_ids(&name)
+                    {
+                        // Pick the first resolvable global type cache as the owner type.
+                        for decl_id in decl_ids {
+                            if let Some(type_cache) = analyzer
+                                .db
+                                .get_type_index()
+                                .get_type_cache(&(*decl_id).into())
+                            {
+                                explicit_type = Some(type_cache.as_type().clone());
+                                break;
+                            }
+                        }
+                    }
+                }
+
+                // Fall back to the inferred prefix type when no explicit type exists.
+                explicit_type.unwrap_or(prefix_type)
+            } else {
+                // Non-name prefixes keep the inferred prefix type.
+                prefix_type
+            };
+
             index_expr.get_index_key()?;
             let member_id = LuaMemberId::new(index_expr.get_syntax_id(), file_id);
             let member_owner = match prefix_type {
diff --git a/crates/emmylua_code_analysis/src/semantic/type_check/test.rs b/crates/emmylua_code_analysis/src/semantic/type_check/test.rs
index 12e0723fd..8aad34fea 100644
--- a/crates/emmylua_code_analysis/src/semantic/type_check/test.rs
+++ b/crates/emmylua_code_analysis/src/semantic/type_check/test.rs
@@ -1,6 +1,6 @@
 #[cfg(test)]
 mod test {
-    use crate::{DiagnosticCode, VirtualWorkspace};
+    use crate::{DiagnosticCode, LuaType, VirtualWorkspace};
 
     #[test]
     fn test_string() {
@@ -208,4 +208,27 @@ mod test {
         "#
         ));
     }
+
+    #[test]
+    fn test_set_index_expr_owner_prefers_declared_global_type() {
+        let mut ws = VirtualWorkspace::new_with_init_std_lib();
+
+        ws.def_file(
+            "def.lua",
+            r#"
+            table = table
+
+            ---@cast table unknown
+            AFTER_CAST = table
+
+            ---@return integer
+            function table.__sentinel()
+                return 1
+            end
+            "#,
+        );
+
+        assert_eq!(ws.expr_ty("AFTER_CAST"), LuaType::Unknown);
+        assert_eq!(ws.expr_ty("table.__sentinel()"), ws.ty("integer"));
+    }
 }