21 replies

Matching Discriminated Union with String Literal Schema

I'm trying to match over a discriminated union, where the discriminator is a string literal defined with

Schema

Schema

Schema

Schema, but when the schema defines a union of literals (either via

S.literal('first', 'second')

S.literal('first', 'second')

S.literal('first', 'second')

S.literal('first', 'second') or

S.union(S.literal('first'), S.literal('second'))

S.union(S.literal('first'), S.literal('second'))

S.union(S.literal('first'), S.literal('second'))

S.union(S.literal('first'), S.literal('second')), the type in the match becomes

never

never

never

never. Example:

const Shirt = S.struct({
  _tag: S.literal('Red', 'Blue')
})
interface Shirt extends S.To<typeof Shirt> {}

pipe(
  Match.type<Shirt>(),
  Match.tag('Red', x => x)
)

const Shirt = S.struct({
  _tag: S.literal('Red', 'Blue')
})
interface Shirt extends S.To<typeof Shirt> {}

pipe(
  Match.type<Shirt>(),
  Match.tag('Red', x => x)
)

const Shirt = S.struct({
  _tag: S.literal('Red', 'Blue')
})
interface Shirt extends S.To<typeof Shirt> {}

pipe(
  Match.type<Shirt>(),
  Match.tag('Red', x => x)
)

const Shirt = S.struct({
  _tag: S.literal('Red', 'Blue')
})
interface Shirt extends S.To<typeof Shirt> {}

pipe(
  Match.type<Shirt>(),
  Match.tag('Red', x => x)
)

Here

x

x is of type

never

never

never

never, unless I get rid of the second argument to

S.literal

S.literal

S.literal

S.literal.

Is this the expected behavior? Wondering if I have package version problem

Matching Discriminated Union with String Literal Schema

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