Add --no-declaration-casts option to analyzer.

Add --no-declaration-casts option to analyzer.

Adds a flag to disable and enable declaration casts independently
from other casts.

Fixes #29546

BUG=
R=brianwilkerson@google.com, rnystrom@google.com

Committed: https://github.com/dart-lang/sdk/commit/1eb480d2667fa3abe3d290dbceca268f73e078c1

[Leaf, 2017-07-13 00:19:26]

leafp@google.com changed reviewers:
+ brianwilkerson@google.com

[Leaf, 2017-07-13 00:19:27]

This adds a non-exclusive flag --no-assignment-casts for controlling whether
casts of the form 

SomeType x = returnsAssignableToSomeType();

are allowed independently from other kinds of cast.

This should allow flutter to enable --no-implicit-casts by also setting
--assignment-casts so that their idiom of casting by variable binding can
continue to work.

[Bob Nystrom, 2017-07-13 18:07:38]

rnystrom@google.com changed reviewers:
+ rnystrom@google.com

[Bob Nystrom, 2017-07-13 18:07:39]

https://codereview.chromium.org/2976963002/diff/20001/pkg/analyzer/lib/src/ge...
File pkg/analyzer/lib/src/generated/type_system.dart (right):

https://codereview.chromium.org/2976963002/diff/20001/pkg/analyzer/lib/src/ge...
pkg/analyzer/lib/src/generated/type_system.dart:433: } else if (!implicitCasts)
{
I think this might be a little clearer as:

if (isAssignmentCast && !assignementCasts) return false;
if (!implicitCasts) return false;

Or maybe that's not right? Is the "else" needed for the implicitCasts case?

[Brian Wilkerson, 2017-07-19 18:52:37]

lgtm

[Leaf, 2017-07-20 21:36:38]

Description was changed from

==========
Add --no-assignment-casts option to analyzer.

Adds a flag to disable and enable assignment casts independently
from other casts.

BUG=
==========

to

==========
Add --no-declaration-casts option to analyzer.

Adds a flag to disable and enable declaration casts independently
from other casts.

Fixes #29546

BUG=
==========

[Leaf, 2017-07-20 21:37:31]

Per offline feedback, changed to --no-declaration-casts and updated code
accordingly.  Also stopped treating default parameter values as declaration
casts.

PTAL.

https://codereview.chromium.org/2976963002/diff/20001/pkg/analyzer/lib/src/ge...
File pkg/analyzer/lib/src/generated/type_system.dart (right):

https://codereview.chromium.org/2976963002/diff/20001/pkg/analyzer/lib/src/ge...
pkg/analyzer/lib/src/generated/type_system.dart:433: } else if (!implicitCasts)
{
On 2017/07/13 18:07:39, Bob Nystrom wrote:
> I think this might be a little clearer as:
> 
> if (isAssignmentCast && !assignementCasts) return false;
> if (!implicitCasts) return false;
> 
> Or maybe that's not right? Is the "else" needed for the implicitCasts case?

As I've set it up, assignmentCasts always controls whether or not assignment
casts are allowed, so yes, the else is needed: otherwise when assignmentCasts is
true but implicitCasts is false you will reject an assignment cast (which is not
the intention).

[Brian Wilkerson, 2017-07-20 22:20:42]

still lgtm

[Bob Nystrom, 2017-07-20 22:54:21]

On 2017/07/20 22:20:42, Brian Wilkerson wrote:
> still lgtm

Double-plus LGTM.

[Leaf, 2017-07-20 22:55:13]

Description was changed from

==========
Add --no-declaration-casts option to analyzer.

Adds a flag to disable and enable declaration casts independently
from other casts.

Fixes #29546

BUG=
==========

to

==========
Add --no-declaration-casts option to analyzer.

Adds a flag to disable and enable declaration casts independently
from other casts.

Fixes #29546

BUG=
R=brianwilkerson@google.com, rnystrom@google.com

Committed:
https://github.com/dart-lang/sdk/commit/1eb480d2667fa3abe3d290dbceca268f73e078c1
==========

[Leaf, 2017-07-20 22:55:15]

Committed patchset #4 (id:60001) manually as
1eb480d2667fa3abe3d290dbceca268f73e078c1 (presubmit successful).