Instead of compiling to `"" + + (+"-");`, `"#{+}-"'` now gives an appropriate
error message:
[stdin]:1:5: error: unexpected end of interpolation
"#{+}-"
^
This is done by _always_ (instead of just sometimes) wrapping the interpolations
in parentheses in the lexer. Unnecessary parentheses won't be output anyway.
I got tired of updating the tests in test/location.coffee (which I had enough of
in #3770), which relies on implementation details (the exact amount of tokens
generated for a given string of code) to do their testing, so I refactored them
to be less fragile.
05b3707506