Field access of explicit tag type union should prioritize definitions over tag.

[alexnask]

Example:

const Id = enum {
 A, B,
};

const Foo = union(Id) {
 A: A,
 B: B,

 const A = u8;
 const B = void;
};

test "union" {
 assert(Foo.A == Id.A); // This should probably return 'u8' instead of Id.A
}

Also, there should probably be some way to refer to definitions with the same symbols as the enum tags even in auto-generated tag unions (and no-tag unions), or be made a compile error (the current state where there are unreachable definitions is the problem imo).

[alexnask]

@andrewrk

In my opinion the sane thing to do is disallow accessing the tag value through the union type for explicit tag type unions.

For implicit (or extern) tag type unions, perhaps we should disallow definitions that shadow the tag name?

[andrewrk]

For now I made a change to prioritize members over tag values for tagged unions. For implicit tagged unions, you can use @TagType(the_union).Foo to access tag values if for some reason the name is shadowed.

To finish implementing the rest of this proposal:

• add compile error for bare enums when member shadows enum tag name
• add compile error for exern union when member shadows union field name