Issue 6073. Fixes for 'export'.

Issue 6073. Fixes for 'export'.
http://code.google.com/p/dart/issues/detail?id=6073


R=brianwilkerson@google.com
BUG=

Committed: https://code.google.com/p/dart/source/detail?r=13853

[Brian Wilkerson, 2012-10-20 17:39:43]

https://codereview.chromium.org/11226010/diff/1/compiler/java/com/google/dart...
File compiler/java/com/google/dart/compiler/resolver/TopLevelElementBuilder.java
(right):

https://codereview.chromium.org/11226010/diff/1/compiler/java/com/google/dart...
compiler/java/com/google/dart/compiler/resolver/TopLevelElementBuilder.java:86:
if (processedObjects.add(library)) {
I don't understand this. If we've already processed this library, shouldn't we
return without doing any further work? But it looks like we'll skip past the
'if' block to process the imports and exports a second time. It probably won't
hurt anything because we're also adding the imports and exports to the set of
processed objects, but it seems inefficient.

[scheglov, 2012-10-20 18:21:27]

https://codereview.chromium.org/11226010/diff/1/compiler/java/com/google/dart...
File compiler/java/com/google/dart/compiler/resolver/TopLevelElementBuilder.java
(right):

https://codereview.chromium.org/11226010/diff/1/compiler/java/com/google/dart...
compiler/java/com/google/dart/compiler/resolver/TopLevelElementBuilder.java:86:
if (processedObjects.add(library)) {
On 2012/10/20 17:39:43, Brian Wilkerson wrote:
> I don't understand this. If we've already processed this library, shouldn't we
> return without doing any further work? But it looks like we'll skip past the
> 'if' block to process the imports and exports a second time. It probably won't
> hurt anything because we're also adding the imports and exports to the set of
> processed objects, but it seems inefficient.

We need this for the case when library A imports B and B imports A, and B
reexports something from C, which is used by A. In this case we process A until
we find import of B, then dive into processing B, process it until import of A,
dive again into processing A but skip all imports which were already process in
A before.

[Brian Wilkerson, 2012-10-20 19:05:18]

LGTM

https://codereview.chromium.org/11226010/diff/1/compiler/java/com/google/dart...
File compiler/java/com/google/dart/compiler/resolver/TopLevelElementBuilder.java
(right):

https://codereview.chromium.org/11226010/diff/1/compiler/java/com/google/dart...
compiler/java/com/google/dart/compiler/resolver/TopLevelElementBuilder.java:86:
if (processedObjects.add(library)) {
> We need this for the case when library A imports B and B imports A, and B
> reexports something from C, which is used by A.

Ah! The joys of mutually recursive libraries! Thanks, I understand now.