feat: added Never case

src/empty.ts

@@ -29,6 +29,8 @@ const go = (ast: AST.AST): Empty<any> => {
     }
 
     switch (ast._tag) {
+        case "NeverKeyword": throw new Error("cannot build an Empty for `never`")
+
         case "Literal": return () => ast.literal
         case "ObjectKeyword": return () => ({})
         case "Tuple": {
@@ -86,6 +88,4 @@ const go = (ast: AST.AST): Empty<any> => {
         case "AnyKeyword":
             return () => undefined
     }
-
-    throw new Error(`unhandled ${ast._tag}`)
 }

src/equivalence.ts

@@ -31,6 +31,8 @@ const go = (ast: AST.AST): Equivalence<any> => {
     }
 
     switch (ast._tag) {
+        case "NeverKeyword": throw new Error("cannot build an Equivalence for `never`")
+
         case "UndefinedKeyword":
         case "UnknownKeyword":
         case "VoidKeyword":
@@ -105,7 +107,4 @@ const go = (ast: AST.AST): Equivalence<any> => {
             };
         }
     }
-
-    throw new Error(`unhandled ${ast._tag}`)
-
 }

src/faker.ts

@@ -40,6 +40,8 @@ const go = (ast: AST.AST, depthLimit = 10): Faker<any> => {
     }
 
     switch (ast._tag) {
+        case "NeverKeyword": throw new Error("cannot build a Faker for `never`")
+
         case "Refinement": return go(ast.from, depthLimit)
         case "Transform": return go(ast.to, depthLimit)
         case "Declaration": return go(ast.type, depthLimit)

src/semigroup.ts

@@ -34,6 +34,8 @@ const go = (ast: AST.AST): Semigroup<any>  => {
     }
 
     switch (ast._tag) {
+        case "NeverKeyword": throw new Error("cannot build a Semigroup for `never`")
+
         case "Literal": 
         case "ObjectKeyword": 
         case "BigIntKeyword": 
@@ -116,6 +118,4 @@ const go = (ast: AST.AST): Semigroup<any>  => {
             }
         }
     }
-
-    throw new Error(`unhandled ${ast._tag}`)
 }

tests/empty.test.ts

@@ -41,6 +41,12 @@ describe("empty", () => {
         })
     })
 
+    it("never", () => {
+        expect(() => _.to(S.never)()).toThrowError(
+            new Error("cannot build an Empty for `never`")
+        );
+    });
+
     it("custom empty", () => {
         const schema = pipe(S.number, _.empty(() => 1))
         expectEmptyValues(schema, 1, 1)

tests/equivalence.test.ts

@@ -33,6 +33,12 @@ describe("equivalence", () => {
         })
     })
 
+    it("never", () => {
+        expect(() => _.to(S.never)()).toThrowError(
+            new Error("cannot build an Equivalence for `never`")
+        );
+    });
+
     it("number/ ", () => {
         const schema = pipe(S.number, S.nonNaN())
         const eq = _.to(schema)()

tests/faker.test.ts

@@ -45,6 +45,12 @@ describe("faker", () => {
         generatesValidValue(schema)
     });
 
+    it("never", () => {
+        expect(() => _.to(S.never)(F.faker)).toThrowError(
+            new Error("cannot build a Faker for `never`")
+        );
+    });
+
     it("transform", () => {
         const schema: S.Schema<string, readonly [string]> = pipe(
             S.string,

tests/semigroup.test.ts

@@ -35,6 +35,12 @@ describe("semigroup", () => {
         })
     })
 
+    it("never", () => {
+        expect(() => _.to(S.never)()).toThrowError(
+            new Error("cannot build a Semigroup for `never`")
+        );
+    });
+
     it("literal/ ", () => {
         const schema = S.literal("a", "b")
         const { combine } = _.to(schema)()