1.8: empty enums with same local name incorrectly considered same type

[jeffreymorlan]

In 1.8, if you declare two empty enums with the same local name in different modules, they are assignable, in violation of the spec ("different enum types are not assignable to each other"):

module A { export declare enum Id {} }
module B { export declare enum Id {} }
var a: A.Id;
var b: B.Id;
a = b; // TypeScript 1.7 caught the error here, 1.8 does not.

This bug will not occur (i.e. the error will be correctly reported) if

• the enums have different local names,
• one or both of the enums are const, or
• the enums have named values with different names.

[RyanCavanaugh]

This is intentional (see #1748) but we need to update the spec

[jeffreymorlan]

Can I rely on them being unassignable if I make them const?

[RyanCavanaugh]

No. You could add some arbitrarily-named member to them, though.

[zpdDG4gta8XKpMCd]

does it mean enums are no longer nominal?

[RyanCavanaugh]

No. For example:

enum A {
    x
}
enum B {
    x
}

// Still an error
var q: A = B.x;

[RyanCavanaugh]

The spec is now an "archived" artifact and we won't be tracking defects against it anymore.