Reproduction link or steps

REPL

What is expected?

barundefined and fooundefined is output when running the bundled output.

In other words, foo = "foo" + window.foo; and foo = "bar" + window.bar; to be assign to a different variable.

What is actually happening?

barundefined is output twice when running the bundled output.

In other words, foo = "foo" + window.foo; and foo = "bar" + window.bar; are assign to the same variable.

System Info

REPL 1.0.0-beta.38

Any additional comments?

This was fine in 1.0.0-beta.29 and broken since 1.0.0-beta.30.