markExport = name => {
        if (topLevelIsOnce[name]) {
          return markFixedExport(name);
        } else {
          return markLiveExport(name);
        }
      }
Adds an exported name to the module static record private metadata,
indicating whether it is fixed or live depending on whether
there are any assignments to the bound variable except for
its declaration.

This function gets called in the cases where whether the export is
live or fixed depends only on whether the export gets assigned
anywhere outside its declaration: exported function declarations and
exported variables initialized to function declarations.

This method gets called in the transform phase.
The returned hidden variable name may be used to transform
a declaration, particularly for an export class statement.

@param {string} name - the local name of the exported variable.