ng-bind with objects

[kasperlewau]

$scope.expr = { name: 'Mike' };

works
ng-bind=":key:expr.name" // 'Mike'

does not work
ng-bind=":key:expr" // [object Object]

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Need to hook into ng-bind and make it aware of the :key:expr syntax, and evaluate the expr if it is not a primitive.

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Related issue: angular#11716