Accessing nonexistent properties is not checked in JS files

[que-etc]

TypeScript Version: 2.8.0-dev.20180302

Search Terms:

• checkJs
• noImplicitAny
• object
• undefined

Code

const fruits = {
    PINEAPPLE: 'tasty'
};

// Name of the property is mistyped and running this code in JS engines
// will result in a TypeError.
fruits.PINAPPLE.toUpperCase();

Expected behavior:
Following error should be raised if checkJs and noImplicitAny flags are enabled:
Property 'PINAPPLE' does not exist on type '{ PINEAPPLE: string; }'. Did you mean 'PINEAPPLE'?

Actual behavior:
No error is shown.

Related Issues: #16137 - this one describes a similar problem, but for some reason it was closed by reporter.

[ghost]

Probably a bug in the code that allows JS objects created by object literals to be assigned new properties -- but a property access should still be an error.

[mhegazy]

Objects in a .js file are assumed to be open-ended. in other words they behave as if they had { [x:string]: any; } on them.

[typescript-bot]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.