Shorthand syntax for Annotated (Type @ [metadata])

[DavidCEllis (David Ellis)]

I had this comment about a runtime issue in the previous thread that I guess I’d need to re-raise:

Dedicated syntax for `Annotated`

Deferred annotations make using operators potentially problematic at runtime. If a value is not yet defined it’s not possible to know what the operator should do. Annotations don’t necessarily have to be types so annotationlib refuses to guess and defers the whole expression. This makes it impossible to get the other details out of an annotation if any of the names are undefined. Using something like Annotated on the other hand, makes the intention clear and you can retrieve the other informat…

In short, presuming @ for Annotated works the same way as | for Union, if the type is a forward reference the entire annotation becomes an opaque forward reference under Format.FORWARDREF. This would potentially lose all of the metadata until the forward reference could be resolved (see the first example from that link).

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Personally I prefer the explicit Annotated (both due to the runtime issues and for clarity), I would like it more if typing was a lighter import but I’d rather that be a driver for improving the import time of typing over adding more new syntax to avoid the import.