stream: fix `Writable` subclass instanceof checks
Checklist
-
make -j8 test
(UNIX), orvcbuild test nosign
(Windows) passes -
tests and/or benchmarks are included -
commit message follows commit guidelines
Affected core subsystem(s)
stream
Description of change
2a4b068a introduced a regression in where checking instanceof
would fail for Writable
subclasses inside the subclass constructor, i.e. before Writable()
was called.
Also, calling null instanceof Writable
or undefined instanceof Writable
would fail due to accessing the _writableState
property of the target object.
This fixes these problems.
Ref: https://github.com/nodejs/node/pull/8834#issuecomment-253640692