chore(typescript): update to typescript 4 (#611)

BREAKING CHANGE: typescript >= 4.0.2 is required to use ts-auto-mock
Update your typescript dependency to version >= 4.0.2

Author: uittorio

definitelyTypedTests/package-lock.json

@@ -18,8 +18,8 @@
   "dependencies": {
     "cross-var": "^1.1.0",
     "dotenv": "^8.2.0",
-    "ttypescript": "^1.5.10",
-    "typescript": "^3.9.7",
-    "upath": "^1.2.0"
+    "ttypescript": "^1.5.12",
+    "typescript": "^4.1.3",
+    "upath": "^2.0.1"
   }
 }

definitelyTypedTests/package.json

@@ -87,7 +87,7 @@
         "ts-node": "^9.1.1",
         "tsconfig-paths": "^3.9.0",
         "ttypescript": "1.5.12",
-        "typescript": "^3.9.7",
+        "typescript": "^4.1.3",
         "webpack": "^5.10.1",
         "webpack-cli": "^4.2.0",
         "webpack-merge": "^5.7.0",
@@ -99,7 +99,7 @@
         "winston": "^3.3.3"
     },
     "peerDependencies": {
-        "typescript": "^3.9.5"
+        "typescript": "^4.0.2"
     },
     "husky": {
         "hooks": {

package-lock.json

@@ -2,6 +2,7 @@ export function isFunction(
   functionToCheck: unknown
 ): functionToCheck is Function {
   return (
-    functionToCheck && {}.toString.call(functionToCheck) === '[object Function]'
+    !!functionToCheck &&
+    {}.toString.call(functionToCheck) === '[object Function]'
   );
 }