fix(diagnostic): resolve alias types before assign mismatch checks

Author: xuhuanzy

crates/emmylua_code_analysis/src/diagnostic/checker/assign_type_mismatch.rs

@@ -7,9 +7,9 @@ use emmylua_parser::{
 use rowan::{NodeOrToken, TextRange};
 
 use crate::{
-    DiagnosticCode, LuaBuiltinAttributeKind, LuaDeclExtra, LuaDeclId, LuaMemberKey,
+    DbIndex, DiagnosticCode, LuaBuiltinAttributeKind, LuaDeclExtra, LuaDeclId, LuaMemberKey,
     LuaSemanticDeclId, LuaType, SemanticDeclLevel, SemanticModel, TypeCheckFailReason,
-    TypeCheckResult, VariadicType, infer_index_expr,
+    TypeCheckResult, VariadicType, get_real_type, infer_index_expr,
 };
 
 use super::{Checker, DiagnosticContext, humanize_lint_type};
@@ -300,7 +300,8 @@ fn check_table_expr_content(
             }
         };
 
-        if (source_type.is_table() || source_type.is_custom_type())
+        let real_source_type = get_real_type_or_self(semantic_model.get_db(), &source_type);
+        if (real_source_type.is_table() || real_source_type.is_custom_type())
             && let Some(table_expr) = LuaTableExpr::cast(value_expr.syntax().clone())
         {
             // 检查子表
@@ -387,7 +388,8 @@ fn check_assign_type_mismatch(
         return Some(false);
     }
 
-    match (&source_type, &value_type) {
+    let real_source_type = get_real_type_or_self(semantic_model.get_db(), source_type);
+    match (real_source_type, value_type) {
         // 如果源类型是定义类型, 则仅在目标类型是定义类型或引用类型时进行类型检查
         (LuaType::Def(_), LuaType::Def(_) | LuaType::Ref(_)) => {}
         (LuaType::Def(_), _) => return Some(false),
@@ -452,3 +454,7 @@ fn add_type_check_diagnostic(
         }
     }
 }
+
+fn get_real_type_or_self<'a>(db: &'a DbIndex, ty: &'a LuaType) -> &'a LuaType {
+    get_real_type(db, ty).unwrap_or(ty)
+}

crates/emmylua_code_analysis/src/diagnostic/test/assign_type_mismatch_test.rs

@@ -1000,6 +1000,49 @@ return t
         ));
     }
 
+    #[test]
+    fn test_optional_alias_field_rejects_table_literal_regardless_of_declaration_order() {
+        let mut ws = VirtualWorkspace::new();
+        assert!(!ws.has_no_diagnostic(
+            DiagnosticCode::AssignTypeMismatch,
+            r#"
+            ---@alias B true?
+
+            ---@class A
+            ---@field field B
+
+            ---@type A
+            local var = { field = {} }
+        "#
+        ));
+
+        assert!(!ws.has_no_diagnostic(
+            DiagnosticCode::AssignTypeMismatch,
+            r#"
+            ---@alias B true?
+
+            ---@class A
+            ---@field field? B
+
+            ---@type A
+            local var = { field = {} }
+        "#
+        ));
+
+        assert!(!ws.has_no_diagnostic(
+            DiagnosticCode::AssignTypeMismatch,
+            r#"
+            ---@class A
+            ---@field field? B
+
+            ---@alias B true?
+
+            ---@type A
+            local var = { field = {} }
+        "#
+        ));
+    }
+
     #[test]
     fn test_issue_525() {
         let mut ws = VirtualWorkspace::new();