Infer Null for return type of functions with empty returns.

Infer Null for return type of functions with empty returns.

This allows inference to infer Null as the return type of functions
which have no return statements, or which return with no value.

Also allows inference to propagate Null.

Fixes https://github.com/dart-lang/sdk/issues/28602
Fixes https://github.com/dart-lang/sdk/issues/28630

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

Committed: https://github.com/dart-lang/sdk/commit/a3b4366f11bee47b818b263b75adf0617f319563

[Leaf, 2017-02-03 02:42:09]

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

[Brian Wilkerson, 2017-02-03 14:41:45]

lgtm

https://codereview.chromium.org/2667343005/diff/20001/pkg/analyzer/test/gener...
File pkg/analyzer/test/generated/strong_mode_test.dart (right):

https://codereview.chromium.org/2667343005/diff/20001/pkg/analyzer/test/gener...
pkg/analyzer/test/generated/strong_mode_test.dart:1175:
test_futureOrNill_no_return_value() async {
"Nill" --> "Null"

[Jennifer Messerly, 2017-02-03 18:47:53]

https://codereview.chromium.org/2667343005/diff/20001/pkg/analyzer/lib/src/ge...
File pkg/analyzer/lib/src/generated/error_verifier.dart (right):

https://codereview.chromium.org/2667343005/diff/20001/pkg/analyzer/lib/src/ge...
pkg/analyzer/lib/src/generated/error_verifier.dart:2312: expectedReturnType,
_typeProvider.futureOrNullType)) {
If I have:

    Future<Null> foo() {
      return;
    }

shouldn't that be a RETURN_WITHOUT_VALUE?

[Leaf, 2017-02-06 18:01:05]

Description was changed from

==========
Infer Null for return type of functions with empty returns.

This allows inference to infer Null as the return type of functions
which have no return statements, or which return with no value.

Also allows inference to propagate Null.

Fixes https://github.com/dart-lang/sdk/issues/28602

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

to

==========
Infer Null for return type of functions with empty returns.

This allows inference to infer Null as the return type of functions
which have no return statements, or which return with no value.

Also allows inference to propagate Null.

Fixes https://github.com/dart-lang/sdk/issues/28602
Fixes https://github.com/dart-lang/sdk/issues/28630

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

[Leaf, 2017-02-06 18:27:15]

PTAL, thanks!

I piggy backed on a small fix for 28630, since it was blocking this CL as well. 
See comment in checker.dart and the new test in checker_test.dart.

https://codereview.chromium.org/2667343005/diff/20001/pkg/analyzer/lib/src/ge...
File pkg/analyzer/lib/src/generated/error_verifier.dart (right):

https://codereview.chromium.org/2667343005/diff/20001/pkg/analyzer/lib/src/ge...
pkg/analyzer/lib/src/generated/error_verifier.dart:2312: expectedReturnType,
_typeProvider.futureOrNullType)) {
On 2017/02/03 18:47:53, Jennifer Messerly wrote:
> If I have:
> 
>     Future<Null> foo() {
>       return;
>     }
> 
> shouldn't that be a RETURN_WITHOUT_VALUE?

Good catch, thanks!  Fixed to keep it simple for now.

https://codereview.chromium.org/2667343005/diff/20001/pkg/analyzer/test/gener...
File pkg/analyzer/test/generated/strong_mode_test.dart (right):

https://codereview.chromium.org/2667343005/diff/20001/pkg/analyzer/test/gener...
pkg/analyzer/test/generated/strong_mode_test.dart:1175:
test_futureOrNill_no_return_value() async {
On 2017/02/03 14:41:45, Brian Wilkerson wrote:
> "Nill" --> "Null"

Done.

https://codereview.chromium.org/2667343005/diff/40001/pkg/analyzer/lib/src/ta...
File pkg/analyzer/lib/src/task/strong/checker.dart (right):

https://codereview.chromium.org/2667343005/diff/40001/pkg/analyzer/lib/src/ta...
pkg/analyzer/lib/src/task/strong/checker.dart:57: } else if (expression is
NamedExpression) {
This fixes 28630, where we were not treating named parameters as concrete
functions.

[Jennifer Messerly, 2017-02-06 20:08:09]

lgtm!

https://codereview.chromium.org/2667343005/diff/40001/pkg/analyzer/lib/src/ta...
File pkg/analyzer/lib/src/task/strong/checker.dart (right):

https://codereview.chromium.org/2667343005/diff/40001/pkg/analyzer/lib/src/ta...
pkg/analyzer/lib/src/task/strong/checker.dart:57: } else if (expression is
NamedExpression) {
On 2017/02/06 18:27:15, Leaf wrote:
> This fixes 28630, where we were not treating named parameters as concrete
> functions.

wow this bug has been here for like ever. nice fix!

[Leaf, 2017-02-06 20:24:49]

Description was changed from

==========
Infer Null for return type of functions with empty returns.

This allows inference to infer Null as the return type of functions
which have no return statements, or which return with no value.

Also allows inference to propagate Null.

Fixes https://github.com/dart-lang/sdk/issues/28602
Fixes https://github.com/dart-lang/sdk/issues/28630

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

to

==========
Infer Null for return type of functions with empty returns.

This allows inference to infer Null as the return type of functions
which have no return statements, or which return with no value.

Also allows inference to propagate Null.

Fixes https://github.com/dart-lang/sdk/issues/28602
Fixes https://github.com/dart-lang/sdk/issues/28630

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

Committed:
https://github.com/dart-lang/sdk/commit/a3b4366f11bee47b818b263b75adf0617f319563
==========

[Leaf, 2017-02-06 20:24:50]

Committed patchset #3 (id:40001) manually as
a3b4366f11bee47b818b263b75adf0617f319563 (presubmit successful).

[Paul Berry, 2017-02-07 18:13:02]

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

[Paul Berry, 2017-02-07 18:13:03]

https://codereview.chromium.org/2667343005/diff/40001/pkg/analyzer/lib/src/ge...
File pkg/analyzer/lib/src/generated/resolver.dart (right):

https://codereview.chromium.org/2667343005/diff/40001/pkg/analyzer/lib/src/ge...
pkg/analyzer/lib/src/generated/resolver.dart:9512: _futureOrNullType =
_futureOrType.instantiate(<DartType>[_nullType]);
This line needs to be after line 9517, or a null reference exception will happen
when analyzer is used with old dart SDKs that lack FutureOr<T>.

Fix is here: https://codereview.chromium.org/2683683002