update fasta scanner to always generate INDEX or INDEX_EQ tokens

update fasta scanner to always generate INDEX or INDEX_EQ tokens

* updated scanner to always generate INDEX and INDEX_EQ for "[]" and "[]="
* updated parser to generate ErrorKind.EmptyOptionalParameterList when "[]" detected
* updated unparser to prevent INDEX token from being generated as [][]

Take 2 of https://codereview.chromium.org/2744463003/

Fix https://github.com/dart-lang/sdk/issues/28665

Committed: https://github.com/dart-lang/sdk/commit/deb6eb8f8261e03b7191bad4c6f74b9654805c25

[danrubel, 2017-03-13 14:58:29]

danrubel@google.com changed reviewers:
+ ahe@google.com

[danrubel, 2017-03-13 14:58:30]

Same as prior CL except
* fixed comment
* tweaked code in
https://codereview.chromium.org/2747683003/diff/1/pkg/front_end/lib/src/fasta...

[danrubel, 2017-03-13 14:59:47]

Description was changed from

==========
update fasta scanner to always generate INDEX or INDEX_EQ tokens

* updated scanner to always generate INDEX and INDEX_EQ for "[]" and "[]="
* updated parser to generate ErrorKind.EmptyOptionalParameterList when "[]"
detected
* updated unparser to prevent INDEX token from being generated as [][]

Take 2 of https://codereview.chromium.org/2744463003/

Fix https://github.com/dart-lang/sdk/issues/28665
==========

to

==========
update fasta scanner to always generate INDEX or INDEX_EQ tokens

* updated scanner to always generate INDEX and INDEX_EQ for "[]" and "[]="
* updated parser to generate ErrorKind.EmptyOptionalParameterList when "[]"
detected
* updated unparser to prevent INDEX token from being generated as [][]

Take 2 of https://codereview.chromium.org/2744463003/

Fix https://github.com/dart-lang/sdk/issues/28665

Committed:
https://github.com/dart-lang/sdk/commit/deb6eb8f8261e03b7191bad4c6f74b9654805c25
==========

[danrubel, 2017-03-13 14:59:49]

Committed patchset #2 (id:20001) manually as
deb6eb8f8261e03b7191bad4c6f74b9654805c25 (presubmit successful).

[ahe, 2017-06-01 14:45:01]

lgtm

https://codereview.chromium.org/2747683003/diff/20001/pkg/compiler/lib/src/tr...
File pkg/compiler/lib/src/tree/unparser.dart (right):

https://codereview.chromium.org/2747683003/diff/20001/pkg/compiler/lib/src/tr...
pkg/compiler/lib/src/tree/unparser.dart:389: // if the NodeList is a single "[]"
token
if -> If