Deletion of readonly property is allowed

[hamishdh]

TypeScript Version: 2.1.1 / nightly (2.2.0-dev.201xxxxx)

Code

interface Foo {
    readonly Property: string;
}

let bar: Foo = {
    Property: "Baz!"
};

bar.Property = undefined; // Disallowed - Cannot Assign to 'Property' because it is a constant or a read-only property
delete bar.Property; // Allowed

Expected behavior:

The TS compiler should disallow deletion of a read-only property.

Actual behavior:

The TS compiler allows deletion of a read-only property.

[RyanCavanaugh]

See #11480. Please search before logging new issues and please fill in a correct version number in the template. This is now an error.

error TS2704: The operand of a delete operator cannot be a read-only property