Error since upgrading to 1.6.1

[quentez]

We're making extensive use of Tagged Unions, and since upgrading to 1.6.1 we're now getting an error right when we declare our types:

Everything was working well in 1.6.0.

Our use-case in that file is pretty big and I can't just post it here. I'll have to try and reproduce it with a simpler case. The only thing I can see right now is that we're building a Tagged Union of Intersections (with the tag property being in one branch of the intersection).

[gcanti]

@quentez not sure if is the same bug but the following throws with the same message

// Note: this intersection always fails while decoding a value
const A = t.intersection([t.type({ type: t.literal('A') }), t.type({ type: t.literal('B') })])
const B = t.type({ type: t.literal('B') })
const C = t.taggedUnion('type', [A, B])

[gcanti]

@quentez looks like the issue is also related to io-ts not being able to build a tagged union under some conditions.

We're making extensive use of Tagged Unions

I need your help, I just released a patch (1.6.4) that should fix this issue.
I also added a warning to the console if I can't build a tagged union.

Example

const A = t.type({ type: t.literal('A'), a: t.number }, 'A')
const B = t.refinement(A, x => x.a > 0, 'B')
const T = t.taggedUnion('type', [B, A]) // type-checks but T is not a tagged union

In this case taggedUnion does two things:

• prints to the console a warning (like "[io-ts] Cannot build a tagged union for (B | A), returning a de-optimized union")
• returns a de-optimized union

Could you please try it out?

[quentez]

@gcanti Version 1.6.4 is working without any issue.
(And I'm not seeing the warning, so that's good).

Thank you for the super quick turnaround 🙂 !

[gcanti]

@quentez great, thanks for the bug report and the feedback