Fix inline tag with code

[TimothyGu]

The cause of this problem is in how inline tags work: you encounter #[, then you take the rest of the line and feeds it into a new lexer. Using a special option this.interpolated and a flag this.ended, the child lexer returns whatever it can lex (i.e. the interpolated part) and the rest (after the interpolation) is fed back to the parent lexer from child.input.

For text, it works well, since can't really have ] as a valid part of the text, so one can just use indexOf(']') for the ending index of the interpolation.

Right now for code, it just feeds the entire rest of the line to the token, which in many cases will not be valid JS and caught in the assertExpression below. Plus, with code one never knows when code
starts or ends, if the ']' is in quotes or not. So one has to be cautious when consuming the strings, not using the crude indexOf check, which is what I am doing here.

This also fixes pugjs/pug#1871.

Depends on ForbesLindesay/character-parser#12.

This should be merged in conjunction with pugjs/pug#2049.

[ForbesLindesay]

How does this handle code like:

- var index = Math.floor(Math.random() * 3);
p #[strong= ['a', 'b', 'c'][index]];

We could use characterParser.parseMax(code) and then check that the next character is ]?

[TimothyGu]

I did not want to use parseMax, since consider this case:

p #[strong= ['a', 'b', 'c'][index]};

We could throw an error about "bracket mismatch," but that doesn't feel intuitive. One would expect the lexer to throw "no ending bracket found" since that is the most direct error.

And for this reason, I wrote ForbesLindesay/character-parser#12, which will allow ['a', 'b', 'c'][index]}; to be the source as long as there is a trailing ], and throw the correct error if not.