Untagged variant accepts @as number literals that are the same JavaScript number #8953

An untagged variant accepts two @as number literals that are the same JavaScript number, when they are spelled differently.

@unboxed type t = | @as(1) A | @as(1.0) B
let name = v => switch v { | A => "A" | B => "B" }
@inline(never) let id = x => x
Console.log2(name(B), name(id(B)))

Output: B A. B is the number 1 at run time, so a dispatched B matches A, while the folded name(B) returns "B".

The same holds for @as(1) A | @as(4294967297) B, because int literals are emitted as 32-bit: name(id(B)) returns "A".

Expected: the declaration is rejected, as for two @as(1) cases, because the literals are equal as JavaScript values.

The duplicate-literal check compares literals by spelling. The rule and its tests are in compiler/ml/UntaggedVariants.md (rule 6), in #8952.