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

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

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

S.literal('first', '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

. 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)
)

Here

is of type

never

never

, unless I get rid of the second argument to

S.literal

S.literal

.

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

Effect Community•3y ago•

21 replies

bsluther

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

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

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

S.literal('first', '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

. 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)
)

Here

is of type

never

never

, unless I get rid of the second argument to

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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