Avoid default constructing code_expressiont

The default constructor is deprecated.

Author: tautschnig

src/cpp/cpp_constructor.cpp

@@ -144,9 +144,7 @@ optionalt<codet> cpp_typecheckt::cpp_constructor(
       side_effect_expr_assignt assign(
         object_tc, operands_tc.front(), typet(), source_location);
       typecheck_side_effect_assignment(assign);
-      code_expressiont new_code;
-      new_code.expression()=assign;
-      return std::move(new_code);
+      return code_expressiont(std::move(assign));
     }
     else
     {

src/cpp/cpp_typecheck_code.cpp

@@ -244,8 +244,7 @@ void cpp_typecheckt::typecheck_member_initializer(codet &code)
       }
     }
 
-    code_expressiont code_expression;
-    code_expression.expression()=function_call;
+    code_expressiont code_expression(function_call);
 
     code.swap(code_expression);
   }