Propertly tree shake factory constructors.

Propertly tree shake factory constructors.

An invocation of a factory constructor on class A does not necessarily
cause class A to be instantiated--it may redirect to a related or
unrelated class, or instantiate nothing at all.

We handle this by treating constructors similar to static function
calls--when a constructor invocation is found, the constructor element
is added to the queue; later, when the constructor element is
analyzed, we determine whether it instantiates the class or not based
on what kind of constructor it is.

R=brianwilkerson@google.com

Committed: https://code.google.com/p/dart/source/detail?r=40899

[Paul Berry, 2014-10-02 21:02:12]

paulberry@google.com changed reviewers:
+ brianwilkerson@google.com, johnniwinther@google.com

[Brian Wilkerson, 2014-10-02 21:26:25]

LGTM

[Johnni Winther, 2014-10-03 08:03:06]

https://codereview.chromium.org/611153003/diff/1/pkg/analyzer2dart/lib/src/tr...
File pkg/analyzer2dart/lib/src/tree_shaker.dart (right):

https://codereview.chromium.org/611153003/diff/1/pkg/analyzer2dart/lib/src/tr...
pkg/analyzer2dart/lib/src/tree_shaker.dart:329: void
visitConstructorDeclaration(ConstructorDeclaration node) {
Currently we only mark classes as instantiated but we need to be more precise
and register directly instantiated type also in the face of redirecting factory
constructors. 

For instance we should know that only Foo<int> has been (directly) instantiated
and Bar<List<int>> has been indirectly instantiated in the following:

class Bar<T> {}
class Foo<T> extends Bar<List<T>> implements Baz<T> {}
class Baz<T> {
  factory Baz() = Foo<T>;
}
main() => new Baz<int>();

[Paul Berry, 2014-10-03 15:50:45]

https://codereview.chromium.org/611153003/diff/1/pkg/analyzer2dart/lib/src/tr...
File pkg/analyzer2dart/lib/src/tree_shaker.dart (right):

https://codereview.chromium.org/611153003/diff/1/pkg/analyzer2dart/lib/src/tr...
pkg/analyzer2dart/lib/src/tree_shaker.dart:329: void
visitConstructorDeclaration(ConstructorDeclaration node) {
On 2014/10/03 08:03:06, Johnni Winther wrote:
> Currently we only mark classes as instantiated but we need to be more precise
> and register directly instantiated type also in the face of redirecting
factory
> constructors. 
> 
> For instance we should know that only Foo<int> has been (directly)
instantiated
> and Bar<List<int>> has been indirectly instantiated in the following:
> 
> class Bar<T> {}
> class Foo<T> extends Bar<List<T>> implements Baz<T> {}
> class Baz<T> {
>   factory Baz() = Foo<T>;
> }
> main() => new Baz<int>();

Ok.  Currently I am only keeping track of what's being directly instantiated.  I
believe this CL moves us into a positive direction since it the behavior without
the CL is to consider Baz<int> to be directly instantiated (which is completely
wrong) and the behavior with the CL is to consider Foo<int> to be directly
instantiated (which is correct, insofar as direct instantiation goes).  So I'm
going to go ahead and commit this CL.

I had been avoiding the issue of "indirectly instantiated" because I don't
completely understand what it means yet.  I'll send you a separate email with
clarifying questions about that.

[Paul Berry, 2014-10-03 15:53:52]

Committed patchset #1 (id:1) manually as 40899 (presubmit successful).

[Johnni Winther, 2014-10-06 10:19:20]

LGTM