This kind of broken command does not have a position information, and
was producing a panic message in the server because it makes the
reasonable assumption that every command returned by `parserCommand`
has a position.
After a parser error in a command, we are "swallowing" all command
parsing errors until a command was succesfully parsed.
This was producing counterintuitive behavior in the IDEs.
@Kha Before this commit, we were producing the error "expected command" at the `let` token
```lean
check id let x := 1; x
```
The new error is "expected command, but found term; this error may be
due to parsing precedence levels, consider parenthesizing the term".
The example above looks artificial, but it will happen all the time as
users start to define their own notation.
@Kha I am also tracking `currNamespace` and `openDecls`.
BTW, I also tried an experiment where I added `currNamespace` and
`openDecls` to `Meta.Context`, but it looked weird. This information
is only needed in the elaborator and pretty printer.
The `PPContext` object should contain everything you need. You
can put `currNamespace` and `openDecls` in the `Delaborator.Context`.
