Arrays can be treated as string-indexable types

[kujon]

TypeScript Version: 2.4.0
Code

const foo: { [index: string]: any } = [42];

Expected behavior:
The code above doesn't compile.

Actual behavior:
Typescript silently accepts such code.

[RyanCavanaugh]

You can think of it this way - for the purposes of indexing, number is a subtype of string due to how JavaScript works

[JRGranell]

@RyanCavanaugh - could this be addressed in strict-mode?

In strict mode, not all JS is a valid TS (e.g. no implicit any), therefore this presents an opportunity to discourage const foo = {'42': 'foo'}; const bar = foo[42] in favour of stricter typings.

Alternatively I would be interested in in other approaches or workarounds given that assigning an array to what is expected to be an object could have significant issues at run-time.

[RyanCavanaugh]

Arrays are objects.