fix metatable

Author: xuhuanzy

crates/emmylua_code_analysis/src/compilation/test/metatable_test.rs

@@ -70,8 +70,36 @@ mod test {
             "#,
         );
 
-        // let ty = ws.expr_ty("a");
-        // disable test temp
-        // assert_eq!(ws.humanize_type(ty), "switch");
+        let ty = ws.expr_ty("a");
+        assert_eq!(ws.humanize_type(ty), "switch");
+    }
+
+    #[test]
+    fn test_issue_599() {
+        let mut ws = VirtualWorkspace::new();
+
+        ws.def(
+            r#"
+            ---@class Class.Config
+            ---@field abc string
+            local ClassConfigMeta = {}
+
+            ---@type table<string, Class.Config>
+            local _classConfigMap = {}
+
+
+            ---@param name string
+            ---@return Class.Config
+            local function getConfig(name)
+                local config = _classConfigMap[name]
+                if not config then
+                    A = setmetatable({ name = name }, { __index = ClassConfigMeta })
+                end
+            end
+            "#,
+        );
+
+        let ty = ws.expr_ty("A");
+        assert_eq!(ws.humanize_type(ty), "Class.Config");
     }
 }

crates/emmylua_code_analysis/src/semantic/infer/infer_call/infer_setmetatable.rs

@@ -1,8 +1,9 @@
 use emmylua_parser::{LuaAstNode, LuaCallExpr, LuaExpr, LuaIndexKey};
 
 use crate::{
-    infer_expr, semantic::infer::InferResult, DbIndex, InFiled, InferFailReason, LuaInferCache,
-    LuaInstanceType, LuaType,
+    infer_expr,
+    semantic::{infer::InferResult, member::find_members_with_key},
+    DbIndex, InFiled, InferFailReason, LuaInferCache, LuaInstanceType, LuaMemberKey, LuaType,
 };
 
 pub fn infer_setmetatable_call(
@@ -114,5 +115,15 @@ fn infer_metatable_index_type(
     };
 
     let meta_type = infer_expr(db, cache, metatable)?;
+    if let Some(meta_members) =
+        find_members_with_key(db, &meta_type, LuaMemberKey::Name("__index".into()), false)
+    {
+        if let Some(meta_member) = meta_members.first() {
+            if meta_member.typ.is_custom_type() {
+                return Ok((meta_member.typ.clone(), true));
+            }
+        }
+    }
+
     Ok((meta_type, false))
 }