this._wasm.withMappingCallback(
      mapping => {
        if (mapping.source !== null) {
          mapping.source = this._absoluteSources.at(mapping.source);

          if (mapping.name !== null) {
            mapping.name = this._names.at(mapping.name);
          }
        }
        if (this._computedColumnSpans && mapping.lastGeneratedColumn === null) {
          mapping.lastGeneratedColumn = Infinity;
        }

        aCallback.call(context, mapping);
      },