Imperfect error message for invoking null literal as function

[rhys-vdw]

TypeScript Version: 2.6.1

Code

Minimal:

null()

Actual real-world mistake:

str !== 'hello' && thing !== null (
  <div>blah</div>
)

Expected behavior:

Clear error to the effect of:

Invoking 'null' as a function

Actual behavior:

Technically correct but slightly misleading error:

Object is possibly 'null'

[DanielRosenwasser]

To be consistent, reasonable error message text would be something to the effect of

Cannot invoke an object which is possibly 'null'.
Cannot invoke an object which is possibly 'undefined'.
Cannot invoke an object which is possibly 'null' or 'undefined'.

[remojansen]

I have sent a PR (#20157) for this issue. I was able to pass all the tests locally. I'm hoping that there will be no issues in CI. Please let me know if anything is wrong (This is my first PR for the TS compiler 🎉).

[mhegazy]

thanks @remojansen!