Original description:
Change front_end handling of callable classes.
This CL is the first in a series of CLs to change the handling of
callable classes in Dart 2.0.
For purposes of this description, a "callable class" is a class whose
interface contains a `.call` method.
In Dart 1.0, a callable class was considered to be a subtype of the
`.call` method's function type. This allowed the user to create
custom objects with similar behavior to closures, but with additional
fields and methods.
In Dart 2.0, a callable class is just an ordinary class, with no
subtype relation to any particular function type. (Note however that
it is still permissible for a class to declare that it "implements
Function").
To reduce the amount of code broken by this change, a piece of
syntactic sugar is being added: if an expression whose static type is
a callable class appears where a function type is expected, an
implicit tear-off of the `.call` method is inserted.
Note that it is still possible at compile time to invoke an expression
whose static type is a callable class, and it is still possible at
runtime to invoke an expression whose runtime type is a callable
class; in both cases, this is considered an implicit invocation of the
class's `.call` method. This is unchanged from Dart 1.0 behavior.
This CL introduces test cases for the new behavior, and implements the
implicit tear-off of `.call` in the front end.
Still to be implemented in future CLs:
- Spec text needs to be written.
- DDC/analyzer code needs to be written to perform implicit tear-offs
of `.call`.
- The subtyping algorithm in DDC, analyzer, VM, and dart2js needs to
be changed so that callable classes are no longer considered
subtypes of any particular function type.
- A small corner case involving type parameters still needs to be
addressed (see TODO in
pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart).
Fixes#32064.
Change-Id: I0d397c608321e25ba42cc02aa8a516aa77aa7c9d
Reviewed-on: https://dart-review.googlesource.com/41280
Reviewed-by: Vyacheslav Egorov <vegorov@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
This reverts commit f0a6330db0.
Reason for revert: Broken bots
Original change's description:
> Change front_end handling of callable classes.
>
> This CL is the first in a series of CLs to change the handling of
> callable classes in Dart 2.0.
>
> For purposes of this description, a "callable class" is a class whose
> interface contains a `.call` method.
>
> In Dart 1.0, a callable class was considered to be a subtype of the
> `.call` method's function type. This allowed the user to create
> custom objects with similar behavior to closures, but with additional
> fields and methods.
>
> In Dart 2.0, a callable class is just an ordinary class, with no
> subtype relation to any particular function type. (Note however that
> it is still permissible for a class to declare that it "implements
> Function").
>
> To reduce the amount of code broken by this change, a piece of
> syntactic sugar is being added: if an expression whose static type is
> a callable class appears where a function type is expected, an
> implicit tear-off of the `.call` method is inserted.
>
> Note that it is still possible at compile time to invoke an expression
> whose static type is a callable class, and it is still possible at
> runtime to invoke an expression whose runtime type is a callable
> class; in both cases, this is considered an implicit invocation of the
> class's `.call` method. This is unchanged from Dart 1.0 behavior.
>
> This CL introduces test cases for the new behavior, and implements the
> implicit tear-off of `.call` in the front end.
>
> Still to be implemented in future CLs:
>
> - Spec text needs to be written.
>
> - DDC/analyzer code needs to be written to perform implicit tear-offs
> of `.call`.
>
> - The subtyping algorithm in DDC, analyzer, VM, and dart2js needs to
> be changed so that callable classes are no longer considered
> subtypes of any particular function type.
>
> - A small corner case involving type parameters still needs to be
> addressed (see TODO in
> pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart).
>
> Fixes#32064.
>
> Change-Id: I6a86491047ae467a5e767cb3cc7cecb570b29308
> Reviewed-on: https://dart-review.googlesource.com/40508
> Commit-Queue: Paul Berry <paulberry@google.com>
> Reviewed-by: Kevin Millikin <kmillikin@google.com>
> Reviewed-by: Leaf Petersen <leafp@google.com>
> Reviewed-by: Erik Ernst <eernst@google.com>
TBR=paulberry@google.com,lrn@google.com,leafp@google.com,dmitryas@google.com,eernst@google.com,kmillikin@google.com
Change-Id: Ia3d3a6e46ceee2b2c55938bec95d09d50bbf06a7
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://dart-review.googlesource.com/41240
Reviewed-by: Paul Berry <paulberry@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
This CL is the first in a series of CLs to change the handling of
callable classes in Dart 2.0.
For purposes of this description, a "callable class" is a class whose
interface contains a `.call` method.
In Dart 1.0, a callable class was considered to be a subtype of the
`.call` method's function type. This allowed the user to create
custom objects with similar behavior to closures, but with additional
fields and methods.
In Dart 2.0, a callable class is just an ordinary class, with no
subtype relation to any particular function type. (Note however that
it is still permissible for a class to declare that it "implements
Function").
To reduce the amount of code broken by this change, a piece of
syntactic sugar is being added: if an expression whose static type is
a callable class appears where a function type is expected, an
implicit tear-off of the `.call` method is inserted.
Note that it is still possible at compile time to invoke an expression
whose static type is a callable class, and it is still possible at
runtime to invoke an expression whose runtime type is a callable
class; in both cases, this is considered an implicit invocation of the
class's `.call` method. This is unchanged from Dart 1.0 behavior.
This CL introduces test cases for the new behavior, and implements the
implicit tear-off of `.call` in the front end.
Still to be implemented in future CLs:
- Spec text needs to be written.
- DDC/analyzer code needs to be written to perform implicit tear-offs
of `.call`.
- The subtyping algorithm in DDC, analyzer, VM, and dart2js needs to
be changed so that callable classes are no longer considered
subtypes of any particular function type.
- A small corner case involving type parameters still needs to be
addressed (see TODO in
pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart).
Fixes#32064.
Change-Id: I6a86491047ae467a5e767cb3cc7cecb570b29308
Reviewed-on: https://dart-review.googlesource.com/40508
Commit-Queue: Paul Berry <paulberry@google.com>
Reviewed-by: Kevin Millikin <kmillikin@google.com>
Reviewed-by: Leaf Petersen <leafp@google.com>
Reviewed-by: Erik Ernst <eernst@google.com>
Paul Berry