No typecheck errors on optional object method param

[giuseppelt]

TypeScript Version: 2.3.4

Code

type MethodOptions = {
    opt1?: string
    opt2?: number
}
class Test {
    method(options?: MethodOptions) {
    }
}

var test = new Test();
test.method("ciao");  //there should be an error here
test.method(1); // idem
test.method([]); // idem

directly on playground

Expected behavior:
Type checking errors

Actual behavior:
No errors

[ikatyang]

In my opinion, MethodOptions is considered to be one of these types:

• {}
• {opt1: string}
• {opt2: number}
• {opt1: string, opt2: number}

So "ciao" | 1 | [] is a valid MethodOptions, since they match the type of {}.

[jwbay]

Duplicate of #7485, fixed by #16047