Definite assignment assertion doesn't work on object-short hand syntax

[tinganho]

TypeScript Version: 2.7.0-dev.201xxxxx

Search Terms:
definite assignment assertion object shorthand

Code

interface A {
    a: string;
}

let As: A[] = [];
let a: string | undefined = 'ff';

function f() {
    As.push({ a! }); // Error
}

Expected behavior:
No error

Actual behavior:

Argument of type '{ a: boolean; }' is not assignable to parameter of type 'A'.
  Types of property 'a' are incompatible.
    Type 'boolean' is not assignable to type 'string'.

Playground Link:
http://www.typescriptlang.org/play/#src=interface%20A%20%7B%0A%20%20%20%20a%3A%20string%3B%0A%7D%0A%0Alet%20As%3A%20A%5B%5D%20%3D%20%5B%5D%3B%0Alet%20a%3A%20string%20%7C%20undefined%20%3D%20'ff'%3B%0A%0Afunction%20f()%20%7B%0A%20%20%20%20As.push(%7B%20a!%20%7D)%3B%20%2F%2F%20Error%0A%7D

Related Issues:

[mhegazy]

PRs welcomed.

[ajafff]

@mhegazy are you sure this is a bug?

This is not a definite assignment assertion. That's a misplaced non-null assertion. There's a parse error at the exclamation mark. Everything is working as expected, only the assignability error is a bit misleading.

You just need to write it as {a: a!}.

#13035 already tracks type assertions on shorthand properties.

[mhegazy]

last time we talked about assertions, it seemed like a good idea to allow them. i do not think this is specifically different.
I think the bug here is a parsing bug. we parsed it as a uniary prefix expression instead of a unary postfix expression. and hence the boolean type.