I hear that you are saying that MetadataAnnotation should be more convenient to use, and we should do something about that.

(You don't need to use the cast operator in Dart, it is completely redundant)

I think the reason why I didn't make MetadataAnnotation an element is because it doesn't have a name. But that is the case for anonymous functions as well. I'll mull this over.

Could you show me an example of what you're trying to do? I'd like to understand the use case better.

Set owner to @peter-ahe-google.
Added Accepted label.

Maybe Spannable is all it needs to be for my purpose:

    PartialMetadataAnnotation partial = annotation;
    compiler.internalError('Annotations needs one string', node: partial.parseNode(compiler));

i.e.
    PartialMetadataAnnotation partial = annotation;
    compiler.internalError('Annotations needs one string', node: partial.parseNode(compiler));
-->
    compiler.internalError('Annotations needs one string', node: annotation);

OK, I have started a CL for making MetadataAnnotation spannable.

Added Started label.

This is the direction I'm going: https://codereview.chromium.org/11428086

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Removed this from the Later milestone.
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Fixed in r18129.