Error: Type cannot be used to index type after two indexes

TypeScript Version: 2.7.1, 2.8.0-dev.20180208

Search Terms:
Type cannot be used to index type

Code

interface IExample {
    foo: {
        bar: {
            baz: number;
        }
    }
}

type F = <
    name extends keyof IExample,
    val extends keyof IExample[name]
>() => IExample[name][val]['baz']; // ← Type '"baz"' cannot be used to index type 'IExample[name][val]'.

Expected behavior:
In version 2.7.0-dev.20171115 this code was checking without errors.

Actual behavior:
Now in throws error: Type '"baz"' cannot be used to index type 'IExample[name][val]'.

Playground Link:
https://www.typescriptlang.org/play/index.html#src=interface%20IExample%20%7B%0D%0A%20%20%20%20foo%3A%20%7B%0D%0A%20%20%20%20%20%20%20%20bar%3A%20%7B%0D%0A%20%20%20%20%20%20%20%20%20%20%20%20baz%3A%20number%3B%0D%0A%20%20%20%20%20%20%20%20%7D%0D%0A%20%20%20%20%7D%0D%0A%7D%0D%0A%0D%0Atype%20F%20%3D%20%3C%0D%0A%20%20%20%20name%20extends%20keyof%20IExample%2C%0D%0A%20%20%20%20val%20extends%20keyof%20IExample%5Bname%5D%0D%0A%3E()%20%3D%3E%20IExample%5Bname%5D%5Bval%5D%5B'baz'%5D%3B

Start with the TypeScript Playground reproduction in the issue and compare its behavior across the reported compiler versions, focusing on the generic indexed-access expression IExample[name][val]['baz']. Trace the type-checking path for the second indexed access and verify that the example checks without errors when the fix is complete.