Adjusted initializer rules, changing a run-time error to compile-time.

Adjusted initializer rules, changing a run-time error to compile-time.

R=lrn@google.com

Committed: https://github.com/dart-lang/sdk/commit/3b5874a332b24f326775b3520f32b9a818731aca

[eernst, 2017-04-25 12:19:20]

eernst@google.com changed reviewers:
+ lrn@google.com

[eernst, 2017-04-25 12:19:21]

One think to consider: I do not think there can be such a
initialization-of-final conflict at runtime any more, so I deleted the phrase
about that situation. If you can see remaining cases where they can arise then
we should fix them, too.

[Lasse Reichstein Nielsen, 2017-04-25 16:00:23]

https://codereview.chromium.org/2843733002/diff/1/docs/language/dartLangSpec.tex
File docs/language/dartLangSpec.tex (right):

https://codereview.chromium.org/2843733002/diff/1/docs/language/dartLangSpec....
docs/language/dartLangSpec.tex:1419: It is a compile-time error if $k$'s
initializer list contains an initializer for a variable that is initialized by
means of an initializing formal of $k$.
Interesting that this is an error, even if it's not a final variable, but I
guess we still consider this a "local" duplicate.

https://codereview.chromium.org/2843733002/diff/1/docs/language/dartLangSpec....
docs/language/dartLangSpec.tex:1420: It is a compile-time error if $k$'s
initializer list contains an initializer for a final variable $f$ whose
declaration includes an initialization expression.
Should we handle the case of initializing formal + initialization expression of
final variable here too?
And having two formal initializers with the same name? (Or is that handled by it
introducing the same name to the scope twice?)

That would make all the dedup-rules be together.

[eernst, 2017-05-19 11:17:02]

PTAL. I think we agreed to make the missing case an error, which is how it is
specified now.

https://codereview.chromium.org/2843733002/diff/1/docs/language/dartLangSpec.tex
File docs/language/dartLangSpec.tex (right):

https://codereview.chromium.org/2843733002/diff/1/docs/language/dartLangSpec....
docs/language/dartLangSpec.tex:1419: It is a compile-time error if $k$'s
initializer list contains an initializer for a variable that is initialized by
means of an initializing formal of $k$.
On 2017/04/25 16:00:23, Lasse Reichstein Nielsen wrote:
> Interesting that this is an error, even if it's not a final variable, but I
> guess we still consider this a "local" duplicate.

Acknowledged. I think the clashes "2 initializers", "initializer + init.formal"
are so semantically similar and so local that it makes sense to treat them
identically as an error.

https://codereview.chromium.org/2843733002/diff/1/docs/language/dartLangSpec....
docs/language/dartLangSpec.tex:1420: It is a compile-time error if $k$'s
initializer list contains an initializer for a final variable $f$ whose
declaration includes an initialization expression.
On 2017/04/25 16:00:23, Lasse Reichstein Nielsen wrote:
> Should we handle the case of initializing formal + initialization expression
of
> final variable here too?
> And having two formal initializers with the same name? (Or is that handled by
it
> introducing the same name to the scope twice?)

Yep, that's (now) a name clash in the formal parameter initializer scope, so we
don't need to specify any other errors there.
 
> That would make all the dedup-rules be together.

As far as I can see, the rule that makes "init.formal + final variable
initializer" an error (or even mentions this case) is new, but we discussed it
and I think we agreed to include it.

I just created an issue (#29656) such that we will get it implemented and have
some test cases.

[Lasse Reichstein Nielsen, 2017-05-19 11:32:33]

lgtm

[eernst, 2017-05-19 12:22:51]

Description was changed from

==========
Adjusted initializer rules, changing a run-time error to compile-time.
==========

to

==========
Adjusted initializer rules, changing a run-time error to compile-time.

R=lrn@google.com

Committed:
https://github.com/dart-lang/sdk/commit/3b5874a332b24f326775b3520f32b9a818731aca
==========

[eernst, 2017-05-19 12:22:53]

Committed patchset #2 (id:20001) manually as
3b5874a332b24f326775b3520f32b9a818731aca (presubmit successful).