dot style assignment not works with indexed object interface

[e-cloud]

TypeScript Version: 2.1.1

Code

interface Dictionary {
    [key: string]: any;
}

const plugins: Dictionary = {}

plugins.test = {}

const plugins2: {
    [key: string]: any;
} = {}

plugins2.test = {}

Expected behavior:
no error

Actual behavior:

Property 'test' does not exist on type 'Dictionary'.
any

See the playground example

IMHO, dot style assignment should infer the property name as string

I think it's related to #6041

[mhegazy]

Duplicate of #12596

[e-cloud]

this has been fixed in v2.2