Populate TypeInferrerImpl.closureContext more frequently.

Populate TypeInferrerImpl.closureContext more frequently.

Previously, we only used a ClosureContext in the case where the
innermost function being inferred was a function expression.  This
meant that we couldn't use the declared return type as the context for
`return` or `yield` statements in any other sort of function.  As a
first step towards fixing that, this CL makes the following changes:

- The entry point to type inference is now a separate
  TypeInferrer.inferFunctionBody method rather than re-using
  TypeInferrer.inferStatement; this gives us an opportunity to set up
  the context.

- Some of the logic from KernelFunctionExpression._inferExpression
  (particularly to do with asynchronous and generator functions) is
  moved to ClosureContext so that it can be used for other sorts of
  functions.

- The only time TypeInferrerImpl.closureContext is ever `null` is now
  when inferring a top level or field initializer expression, so we
  can eliminate some null checks from
  KernelReturnStatement._inferStatement and
  KernelYieldStatement._inferStatement.

R=scheglov@google.com

Committed: https://github.com/dart-lang/sdk/commit/0d31c8c524d73a2265df23113d77204fbe0370aa

[Paul Berry, 2017-05-23 18:01:02]

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

[scheglov, 2017-05-23 18:11:19]

LGTM

[Paul Berry, 2017-05-23 18:21:49]

Description was changed from

==========
Populate TypeInferrerImpl.closureContext more frequently.

Previously, we only used a ClosureContext in the case where the
innermost function being inferred was a function expression.  This
meant that we couldn't use the declared return type as the context for
`return` or `yield` statements in any other sort of function.  As a
first step towards fixing that, this CL makes the following changes:

- The entry point to type inference is now a separate
  TypeInferrer.inferFunctionBody method rather than re-using
  TypeInferrer.inferStatement; this gives us an opportunity to set up
  the context.

- Some of the logic from KernelFunctionExpression._inferExpression
  (particularly to do with asynchronous and generator functions) is
  moved to ClosureContext so that it can be used for other sorts of
  functions.

- The only time TypeInferrerImpl.closureContext is ever `null` is now
  when inferring a top level or field initializer expression, so we
  can eliminate some null checks from
  KernelReturnStatement._inferStatement and
  KernelYieldStatement._inferStatement.
==========

to

==========
Populate TypeInferrerImpl.closureContext more frequently.

Previously, we only used a ClosureContext in the case where the
innermost function being inferred was a function expression.  This
meant that we couldn't use the declared return type as the context for
`return` or `yield` statements in any other sort of function.  As a
first step towards fixing that, this CL makes the following changes:

- The entry point to type inference is now a separate
  TypeInferrer.inferFunctionBody method rather than re-using
  TypeInferrer.inferStatement; this gives us an opportunity to set up
  the context.

- Some of the logic from KernelFunctionExpression._inferExpression
  (particularly to do with asynchronous and generator functions) is
  moved to ClosureContext so that it can be used for other sorts of
  functions.

- The only time TypeInferrerImpl.closureContext is ever `null` is now
  when inferring a top level or field initializer expression, so we
  can eliminate some null checks from
  KernelReturnStatement._inferStatement and
  KernelYieldStatement._inferStatement.

R=scheglov@google.com

Committed:
https://github.com/dart-lang/sdk/commit/0d31c8c524d73a2265df23113d77204fbe0370aa
==========

[Paul Berry, 2017-05-23 18:21:50]

Committed patchset #1 (id:1) manually as
0d31c8c524d73a2265df23113d77204fbe0370aa (presubmit successful).