Fix #374

Author: xuhuanzy

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

@@ -822,6 +822,7 @@ return t
         "#
         ));
     }
+
     #[test]
     fn test_issue_393() {
         let mut ws = VirtualWorkspace::new();
@@ -840,4 +841,21 @@ return t
         "#
         ));
     }
+
+    #[test]
+    fn test_issue_374() {
+        let mut ws = VirtualWorkspace::new();
+        assert!(ws.check_code_for(
+            DiagnosticCode::AssignTypeMismatch,
+            r#"
+                --- @param x? integer
+                --- @return integer?
+                --- @overload fun(): integer
+                function bar(x) end
+
+                --- @type integer
+                local _ = bar() -- - error cannot assign `integer?` to `integer`
+        "#
+        ));
+    }
 }

crates/emmylua_code_analysis/src/semantic/overload_resolve/mod.rs

@@ -86,6 +86,11 @@ fn resolve_signature_by_args(
             jump_param = 0;
         };
 
+        // 如果在不计算可空参数的情况下, 参数数量完全匹配, 则认为其权重更高
+        if params.len() == fake_expr_len {
+            total_weight += params.len() as i32 + 1;
+        }
+
         // 冒号定义且冒号调用
         if is_colon_call && func.is_colon_define() {
             total_weight += 100;