JSAwait

await arg.

This is directly equivalent to a JavaScript await expression.

If used directly within a Closure node with the async flag, this node is always valid. However, when used anywhere else, it is an "orphan" await. Orphan awaits only link when targeting WebAssembly.

This is not a UnaryOp because of the above strict scoping rule. For example, unless it is orphan to begin with, it is not safe to pull this node out of or into an intervening closure, contrary to UnaryOps.