Add missing test in ASTSymbolInitializationChecker

tests/test_ASTSymbolInitializationChecker.cpp

@@ -301,5 +301,18 @@ let f : R->R, x->x+y;
       ASTSymbolTableBuilder{*ast};
       REQUIRE_THROWS_WITH(ASTSymbolInitializationChecker{*ast}, std::string{"uninitialized symbol 'y'"});
     }
+
+    SECTION("expecting a list of identifiers")
+    {
+      std::string_view data = R"(
+let (x,y,z):R*R*R, x = 3;
+)";
+
+      string_input input{data, "test.pgs"};
+      auto ast = ASTBuilder::build(input);
+
+      ASTSymbolTableBuilder{*ast};
+      REQUIRE_THROWS_WITH(ASTSymbolInitializationChecker{*ast}, std::string{"expecting a list of identifiers"});
+    }
   }
 }