Slightly clean-up some code

Should improve readability somehow, and led to better error messages.

src/language/ASTNodeAffectationExpressionBuilder.cpp

@@ -239,7 +239,12 @@ ASTNodeAffectationExpressionBuilder::ASTNodeAffectationExpressionBuilder(ASTNode
         }
         break;
       }
+      case ASTNodeDataType::int_t: {
+        // Nothing to check by now since the special value 0 is allowed
+        break;
+      }
       default: {
+        ASTNodeNaturalConversionChecker{n, data_node.m_data_type, n.m_data_type};
       }
       }
     } else {