includesSourceFile(sourceFile) {
            return this.sourceFilesSet.has(sourceFile.fileName);
          }
It's possible that we will encounter the right side of `export { foo as bar } from "x";` more than once.
For example:
    // b.ts
    export { foo as bar } from "./a";
    import { bar } from "./b";

Normally at `foo as bar` we directly add `foo` and do not locally search for it (since it doesn't declare a local).
But another reference to it may appear in the same source file.
See `tests/cases/fourslash/transitiveExportImports3.ts`.