Add SimpleKeyOf type, resolves #45

Author: rokoroku

tsconfig.json

@@ -10,7 +10,6 @@
     "removeComments": true,
     "noImplicitReturns": true,
     "noUnusedLocals": true,
-    "keyofStringsOnly": true,
     "strict": true,
     "outDir": "build",
     "lib": ["es6", "es7", "dom"],

types/global.d.ts

@@ -7,7 +7,8 @@ declare module '*.css' {
 }
 
 // Omit type https://github.com/Microsoft/TypeScript/issues/12215
+type SimpleKeyOf<T> = Extract<keyof T, 'number' | 'string'>;
 type Diff<T extends string, U extends string> = ({ [P in T]: P } & { [P in U]: never } & { [x: string]: never })[T];
-type Omit<T, K extends keyof T> = { [P in Diff<keyof T, K>]: T[P] };
+type Omit<T, K extends SimpleKeyOf<T>> = { [P in Diff<SimpleKeyOf<T>, K>]: T[P] };
 
 type PartialPick<T, K extends keyof T> = Partial<T> & Pick<T, K>;