Issue 12158. Report error when user code uses 'native' clause.

Issue 12158. Report error when user code uses 'native' clause.
https://code.google.com/p/dart/issues/detail?id=12158

R=brianwilkerson@google.com, jwren@google.com
BUG=

Committed: https://code.google.com/p/dart/source/detail?r=25839

[jwren, 2013-08-06 20:55:17]

On 2013/08/06 20:43:28, scheglov wrote:

LGTM

[Brian Wilkerson, 2013-08-06 22:43:25]

LGTM

[scheglov, 2013-08-06 22:50:31]

Committed patchset #1 manually as r25839 (presubmit successful).

[Bill Hesse, 2013-08-07 08:54:58]

On 2013/08/06 22:50:31, scheglov wrote:
> Committed patchset #1 manually as r25839 (presubmit successful).

Are you aware that native extensions created by users for the Dart standalone
executable use
the 'native' indicator to indicate functions that call into native code?

We have an outstanding bug to change this use of 'native' to an annotation on
the function instead,
but as of right now, user code can be using 'native'.

See samples/sample_extension/sample_extension.dart, for example, and
runtime/bin/test_extension.dart

[Brian Wilkerson, 2013-08-07 13:47:52]

> Are you aware that native extensions created by users for the Dart standalone
> executable use
> the 'native' indicator to indicate functions that call into native code?

Yes, but we were told that because native is not included in the specification
we must produce an error when we see it's use. Sounds like we need to get native
into the specification, along with an explanation of why we need both 'external'
and 'native' and when to use one rather than the other.