Non-null assertion operator non working on properties

[HolgerJeromin]

TypeScript Version: 2.3

Code

export interface Dictionary<T> {
    [index: string]: T | undefined;
}
const name = 'bar';
let foo: Dictionary<number> = {};
if (foo[name] === undefined) {
    foo[name] = 1;
} else {
    let numberOrUndef = foo[name];
    let numb = foo[name]!;
    foo[name]++;
}

last code line foo[name]++; is probably undefined. Ok, it is not, but no problem.
But i cannot override this with the Non-null assertion operator !

foo[name]!++; gives "The operand of an increment or decrement operator must be a variable or a property access."

[mhegazy]

checkReferenceExpression should skip the NonNullExpression just like it does with parenthesized expressions.

[HolgerJeromin]

Ah, thanks for the hint with parenthesis as a workaround.

[mhegazy]

Parenthesis will not work. We already skip these correctelly and will land on the null assertion again and flag it as an error.

[sandersn]

Fix is up at #16465