Is there any reason shorthand property names ({ a }, etc.) don't allow type casting around the names? It would be a mildly useful feature.

Code

The following object literals are all intended to compile to { foo: foo }:

function take(arg: { foo: string }) { }

let foo: string;

// Allowed
take({ foo });
take({ foo: foo });
take({ foo: foo as string });
take({ foo: <string>foo });

// Syntax errors
take({ <string>foo });
take({ foo as string });

Expected behavior:
These should all compile to the same thing.

Actual behavior:
The lines with type casting in the names are syntax errors.