Fix for TypeScript 3.4

Author: pelotom

.vscode/settings.json

@@ -1,3 +1,4 @@
 {
-  "editor.formatOnSave": true
+  "editor.formatOnSave": true,
+  "typescript.tsdk": "node_modules/typescript/lib"
 }

package.json

@@ -19,7 +19,7 @@
     "jest": "^21.2.1",
     "prettier": "^1.11.1",
     "ts-jest": "^21.2.4",
-    "typescript": "^2.8.1"
+    "typescript": "^3.4.1"
   },
   "jest": {
     "verbose": false,
@@ -34,4 +34,4 @@
     "mapCoverage": true,
     "testEnvironment": "node"
   }
-}
+}

src/index.ts

@@ -61,8 +61,8 @@ export type MultiValueVariants<Record extends MultiValueRec, TagProp extends str
     : { [_ in TagProp]: T } & Record[T] // no: decorate with tag
 };
 
-export type UnTagged<Record, TagProp extends string = 'tag'> = Record extends {}
-  ? Pick<Record, { [k in keyof Record]: k extends TagProp ? never : k }[keyof Record]>
+export type UnTagged<Record, TagProp extends string = 'tag'> = Record extends any
+  ? Pick<Record, Exclude<keyof Record, TagProp>>
   : never;
 
 export type SingleValueVariants<
@@ -111,7 +111,7 @@ export function unionize<Record>(record: Record, config?: { value?: string; tag?
 
   const creators = {} as Creators<Record, any, any>;
   for (const tag in record) {
-    creators[tag] = ((value = {}) =>
+    creators[tag] = ((value: any = {}) =>
       valProp ? { [tagProp]: tag, [valProp]: value } : { ...value, [tagProp]: tag }) as any;
   }
 

yarn.lock

@@ -2534,9 +2534,10 @@ type-check@~0.3.2:
   dependencies:
     prelude-ls "~1.1.2"
 
-typescript@^2.8.1:
-  version "2.8.1"
-  resolved "https://registry.yarnpkg.com/typescript/-/typescript-2.8.1.tgz#6160e4f8f195d5ba81d4876f9c0cc1fbc0820624"
+typescript@^3.4.1:
+  version "3.4.1"
+  resolved "https://registry.npmjs.org/typescript/-/typescript-3.4.1.tgz#b6691be11a881ffa9a05765a205cb7383f3b63c6"
+  integrity sha512-3NSMb2VzDQm8oBTLH6Nj55VVtUEpe/rgkIzMir0qVoLyjDZlnMBva0U6vDiV3IH+sl/Yu6oP5QwsAQtHPmDd2Q==
 
 uglify-js@^2.6:
   version "2.8.29"