interface TestType {
   a: number;
   b: string;
   [key:string]: any;
}
type NTestType1 = {
   [P in keyof TestType]: any;
}
const test:NTestType1 = {} // error missing a and b. this is correct.
type NTestType2 = {
   [P in Exclude<keyof TestType, 'a'>]: any;
}
const test::NTestType2 = {} // no error, we expect show missing b error here.