fix(TypeScript): Migrated to TypeScript 2.9

package.json

@@ -39,11 +39,11 @@
   },
   "homepage": "https://github.com/jan-molak/tiny-types#readme",
   "devDependencies": {
-    "@types/chai": "4.1.3",
-    "@types/mocha": "5.2.0",
+    "@types/chai": "4.1.4",
+    "@types/mocha": "5.2.2",
     "@types/node": "10.1.2",
-    "@types/sinon": "5.0.0",
-    "@types/sinon-chai": "2.7.32",
+    "@types/sinon": "5.0.1",
+    "@types/sinon-chai": "3.2.0",
     "chai": "4.1.2",
     "cheerio": "1.0.0-rc.2",
     "commitizen": "2.10.1",
@@ -63,10 +63,10 @@
     "sinon": "5.0.10",
     "sinon-chai": "3.1.0",
     "travis-deploy-once": "5.0.0",
-    "ts-node": "6.0.5",
+    "ts-node": "6.1.1",
     "tslint": "5.10.0",
     "tslint-microsoft-contrib": "5.0.3",
-    "typescript": "2.8.3"
+    "typescript": "2.9.2"
   },
   "config": {
     "commitizen": {

spec/pattern-matching/IdentityMatcher.spec.ts

@@ -39,7 +39,7 @@ describe('pattern-matching', () => {
 
             const result = new IdentityMatcher(s)
                 .when(s, _ => `received "some symbol"`)
-                .else(_ => `else, received "${_}"`);
+                .else(_ => `else, received "${_.toString()}"`);
 
             expect(result).to.equal('received "some symbol"');
         });

src/types/lookup.ts

@@ -21,7 +21,8 @@ export type IsNeverWorker<S extends string> = (
 // Worker needed because of https://github.com/Microsoft/TypeScript/issues/18118
 export type IsNever<T extends string> = Not<HaveIntersection<IsNeverWorker<T>, 'false'>>;
 
-export type IsFunction<T> = IsNever<keyof T>;
+// http://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-9.html
+export type IsFunction<T> = IsNever<Extract<keyof T, string>>;
 
 export type NonFunctionProps<T> = {
     [K in keyof T]: {