Parser NPE on dangling comma in Vector literal

[radeusgd]

What issue are you facing?

Run the following program:

main =
    x = ["a", ]
    IO.println x

Expected behaviour

I would expect to get a syntax error message, showing me the location where I added a malformed vector literal.

Instead, I'm getting:

Execution finished with an error: java.lang.NullPointerException

I'm not sure, but I suspect this issue may potentially also affect GUI stability - as the kind of problematic form [x, ] is often a partial result when adding new elements to a vector when editing a node. So if that goes to the parser and crashes it with NPE, it may be one of the reasons of the engine dying. This is just a hypothesis though. Regardless, it is a bug that is making user mistakes hard to debug.

Enso Version

latest develop + non-parser related changes to stdlib