pretty-printer does not preserve parens in (a = 10).x;

[jruderman]

Issue #890 took care of the simple case, but this more complex case is still broken.

fn g() { (a = 10).x; }

becomes

fn g() { a = 10.x; }

which does not parse.

[jruderman]

Even worse is

fn g() { (a = b).x; }

pretty-printing as

fn g() { a = b.x; }

which does parse but has different semantics.