Depending on the transpiler and mode of operation, `var` is sometimes emitted.

For example, esbuild will emit var when targeting ESM, for performance and minification reasons. Because ESM has its own inherent scope barrier, this is fine, but it won't apply the same optimizations when targeting (e.g.) IIFE, because it's not fine in that context.

https://github.com/evanw/esbuild/issues/1301