Remove some appending behavior from GN.

Remove some appending behavior from GN.

Remove operator += and -= to append/remove a non-list to/from a list. Now you will have to wrap a single item in [] if you want to add or remove it. This makes the syntax more uniform since people were doing it randomly with and without [].

This removes the error of assigning to an unused variable. This ended up being too much of a bother, and causing errors in cases were you wouldn't expect it.

R=scottmg@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=247202

[scottmg, 2014-01-15 00:32:07]

https://codereview.chromium.org/136723008/diff/1/tools/gn/operators.cc
File tools/gn/operators.cc (right):

https://codereview.chromium.org/136723008/diff/1/tools/gn/operators.cc#newcod...
tools/gn/operators.cc:266: if (!right.type() != Value::LIST) {
is !right.type() what you meant?

https://codereview.chromium.org/136723008/diff/1/tools/gn/operators_unittest.cc
File tools/gn/operators_unittest.cc (right):

https://codereview.chromium.org/136723008/diff/1/tools/gn/operators_unittest....
tools/gn/operators_unittest.cc:95: }
can you add a failure test for the disallowed cases?

[brettw, 2014-01-15 23:19:55]

Now with more tests.

[scottmg, 2014-01-15 23:22:01]

lgtm

[brettw, 2014-01-27 07:00:08]

Committed patchset #2 manually as r247202 (presubmit successful).