Minor type inference fixes to do with null and bottom types.

Minor type inference fixes to do with null and bottom types.

This CL makes the following fixes:

- Updates analyzer's front_end_inference_test to represent the bottom
  type as "<BottomType>" (consistent with Kernel).

- Implements type inference of "throw" expressions.

- Does not coerce bottom to dynamic when inferring the return type of
  a closure.

- Does not coerce Null to dynamic when inferring the return type of a
  block closure.

- Ignores bare "return;" statements when inferring the return type of
  a block closure.

- Infers Null when a block closure lacks "return <expression>;"
  statements.

- Implements correct rules for LUB(Null, x), by treating Null as
  bottom.

R=scheglov@google.com

Committed: https://github.com/dart-lang/sdk/commit/830be5727d9e19b3086425ee4d3738c0cbba3771

[Paul Berry, 2017-05-17 03:20:13]

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

[scheglov, 2017-05-17 06:43:40]

LGTM

[Paul Berry, 2017-05-17 12:36:17]

Description was changed from

==========
Minor type inference fixes to do with null and bottom types.

This CL makes the following fixes:

- Updates analyzer's front_end_inference_test to represent the bottom
  type as "<BottomType>" (consistent with Kernel).

- Implements type inference of "throw" expressions.

- Does not coerce bottom to dynamic when inferring the return type of
  a closure.

- Does not coerce Null to dynamic when inferring the return type of a
  block closure.

- Ignores bare "return;" statements when inferring the return type of
  a block closure.

- Infers Null when a block closure lacks "return <expression>;"
  statements.

- Implements correct rules for LUB(Null, x), by treating Null as
  bottom.
==========

to

==========
Minor type inference fixes to do with null and bottom types.

This CL makes the following fixes:

- Updates analyzer's front_end_inference_test to represent the bottom
  type as "<BottomType>" (consistent with Kernel).

- Implements type inference of "throw" expressions.

- Does not coerce bottom to dynamic when inferring the return type of
  a closure.

- Does not coerce Null to dynamic when inferring the return type of a
  block closure.

- Ignores bare "return;" statements when inferring the return type of
  a block closure.

- Infers Null when a block closure lacks "return <expression>;"
  statements.

- Implements correct rules for LUB(Null, x), by treating Null as
  bottom.

R=scheglov@google.com

Committed:
https://github.com/dart-lang/sdk/commit/830be5727d9e19b3086425ee4d3738c0cbba3771
==========

[Paul Berry, 2017-05-17 12:36:18]

Committed patchset #1 (id:1) manually as
830be5727d9e19b3086425ee4d3738c0cbba3771 (presubmit successful).