Prefer unwrap_or_else to unwrap_or in case of function calls/allocations
The contents of `unwrap_or` are evaluated eagerly, so it's not a good pick in case of function calls and allocations. This PR also changes a few `unwrap_or`s with `unwrap_or_default`.
An added bonus is that in some cases this change also reveals if the object it's called on is an `Option` or a `Result` (based on whether the closure takes an argument).
* When encountering EOF, point at the last opening brace that does not
have the same indentation level as its close delimiter.
* When encountering the wrong type of close delimiter, point at the
likely correct open delimiter to give a better idea of what went
wrong.
