Allow Schema.Either to support Never without type errors, closes #3755 (

#3761)
Effect-TS · Oct 9, 2024 · 360ec14 · 360ec14
1 parent 518ef7b
commit 360ec14
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Showing 3 changed files with 35 additions and 7 deletions.
diff --git a/.changeset/wet-balloons-swim.md b/.changeset/wet-balloons-swim.md
@@ -0,0 +1,10 @@
+---
+"@effect/schema": patch
+---
+
+Allow Schema.Either to support Schema.Never without type errors, closes #3755.
+
+- Updated the type parameters of `format` to extend `Schema.All` instead of `Schema<A, I, R>`.
+- Updated the type parameters of `Schema.EitherFromSelf` to extend `Schema.All` instead of `Schema.Any`.
+- Updated the type parameters of `Schema.Either` to extend `Schema.All` instead of `Schema.Any`.
+- Updated the type parameters of `Schema.EitherFromUnion` to extend `Schema.All` instead of `Schema.Any`.
diff --git a/packages/schema/dtslint/Schema.ts b/packages/schema/dtslint/Schema.ts
@@ -2064,6 +2064,12 @@ S.asSchema(S.EitherFromSelf({ right: S.NumberFromString, left: S.String }))
 // $ExpectType EitherFromSelf<typeof NumberFromString, typeof String$>
 S.EitherFromSelf({ right: S.NumberFromString, left: S.String })
 
+// $ExpectType EitherFromSelf<typeof String$, typeof Never>
+S.EitherFromSelf({ right: S.String, left: S.Never })
+
+// $ExpectType EitherFromSelf<typeof Never, typeof String$>
+S.EitherFromSelf({ right: S.Never, left: S.String })
+
 // ---------------------------------------------
 // Either
 // ---------------------------------------------
@@ -2074,6 +2080,12 @@ S.asSchema(S.Either({ right: S.NumberFromString, left: S.String }))
 // $ExpectType Either<typeof NumberFromString, typeof String$>
 S.Either({ right: S.NumberFromString, left: S.String })
 
+// $ExpectType Either<typeof String$, typeof Never>
+S.Either({ right: S.String, left: S.Never })
+
+// $ExpectType Either<typeof Never, typeof String$>
+S.Either({ right: S.Never, left: S.String })
+
 // ---------------------------------------------
 // EitherFromUnion
 // ---------------------------------------------
@@ -2084,6 +2096,12 @@ S.asSchema(S.EitherFromUnion({ right: S.NumberFromString, left: S.Boolean }))
 // $ExpectType EitherFromUnion<typeof NumberFromString, typeof Boolean$>
 S.EitherFromUnion({ right: S.NumberFromString, left: S.Boolean })
 
+// $ExpectType EitherFromUnion<typeof String$, typeof Never>
+S.EitherFromUnion({ right: S.String, left: S.Never })
+
+// $ExpectType EitherFromUnion<typeof Never, typeof String$>
+S.EitherFromUnion({ right: S.Never, left: S.String })
+
 // ---------------------------------------------
 // ReadonlyMapFromSelf
 // ---------------------------------------------

diff --git a/packages/schema/src/Schema.ts b/packages/schema/src/Schema.ts
@@ -242,7 +242,7 @@ export const asSchema = <S extends Schema.All>(
  * @category formatting
  * @since 0.67.0
  */
-export const format = <A, I, R>(schema: Schema<A, I, R>): string => String(schema.ast)
+export const format = <S extends Schema.All>(schema: S): string => String(schema.ast)
 
 /**
  * @since 0.67.0
@@ -6703,7 +6703,7 @@ const eitherParse = <RR, R, LR, L>(
  * @category api interface
  * @since 0.67.0
  */
-export interface EitherFromSelf<R extends Schema.Any, L extends Schema.Any> extends
+export interface EitherFromSelf<R extends Schema.All, L extends Schema.All> extends
   AnnotableClass<
     EitherFromSelf<R, L>,
     either_.Either<Schema.Type<R>, Schema.Type<L>>,
@@ -6716,7 +6716,7 @@ export interface EitherFromSelf<R extends Schema.Any, L extends Schema.Any> exte
  * @category Either transformations
  * @since 0.67.0
  */
-export const EitherFromSelf = <R extends Schema.Any, L extends Schema.Any>({ left, right }: {
+export const EitherFromSelf = <R extends Schema.All, L extends Schema.All>({ left, right }: {
   readonly left: L
   readonly right: R
 }): EitherFromSelf<R, L> => {
@@ -6748,7 +6748,7 @@ const makeRightEncoded = <A>(right: A) => (({
  * @category api interface
  * @since 0.67.0
  */
-export interface Either<R extends Schema.Any, L extends Schema.Any> extends
+export interface Either<R extends Schema.All, L extends Schema.All> extends
   AnnotableClass<
     Either<R, L>,
     either_.Either<Schema.Type<R>, Schema.Type<L>>,
@@ -6761,7 +6761,7 @@ export interface Either<R extends Schema.Any, L extends Schema.Any> extends
  * @category Either transformations
  * @since 0.67.0
  */
-export const Either = <R extends Schema.Any, L extends Schema.Any>({ left, right }: {
+export const Either = <R extends Schema.All, L extends Schema.All>({ left, right }: {
   readonly left: L
   readonly right: R
 }): Either<R, L> => {
@@ -6782,7 +6782,7 @@ export const Either = <R extends Schema.Any, L extends Schema.Any>({ left, right
  * @category api interface
  * @since 0.67.0
  */
-export interface EitherFromUnion<R extends Schema.Any, L extends Schema.Any> extends
+export interface EitherFromUnion<R extends Schema.All, L extends Schema.All> extends
   AnnotableClass<
     EitherFromUnion<R, L>,
     either_.Either<Schema.Type<R>, Schema.Type<L>>,
@@ -6801,7 +6801,7 @@ export interface EitherFromUnion<R extends Schema.Any, L extends Schema.Any> ext
  * @category Either transformations
  * @since 0.67.0
  */
-export const EitherFromUnion = <R extends Schema.Any, L extends Schema.Any>({ left, right }: {
+export const EitherFromUnion = <R extends Schema.All, L extends Schema.All>({ left, right }: {
   readonly left: L
   readonly right: R
 }): EitherFromUnion<R, L> => {