Error inferring types of promise function

TypeScript Version: nightly (Version 2.5.0-dev.20170816)

Code

(based on DefinitelyTyped/types/bluebird/index.d.ts)

declare function props<K, V>(x: PromiseLike<Map<K, PromiseLike<V> | V>>): Promise<Map<K, V>>;
declare const input: Promise<Map<number, Promise<string>>>;
const out: Promise<Map<number, string>> = props(input);

Expected behavior:

No error.

Actual behavior:

src/a.ts(3,7): error TS2322: Type 'Promise<Map<number, Promise<string>>>' is not assignable to type 'Promise<Map<number, string>>'.
  Type 'Map<number, Promise<string>>' is not assignable to type 'Map<number, string>'.
    Type 'Promise<string>' is not assignable to type 'string'.

It works if I explicitly specify props<number, string>(input).
The error only reproduces with "lib": ["es6"].

[rubiesonthesky]

This is still giving error, here is repro for bot.

declare function props<K, V>(x: PromiseLike<Map<K, PromiseLike<V> | V>>): Promise<Map<K, V>>;
declare const input: Promise<Map<number, Promise<string>>>;
const out: Promise<Map<number, string>> = props(input);

Workbench Repro

[typescript-bot]

👋 Hi, I'm the Repro bot. I can help narrow down and track compiler bugs across releases! This comment reflects the current state of this repro running against the nightly TypeScript.

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Comment by @rubiesonthesky

❌ Failed: -

• Type 'Promise>>' is not assignable to type 'Promise>'. Type 'Map>' is not assignable to type 'Map'. Type 'Promise' is not assignable to type 'string'.

Historical Information

Version	Reproduction Outputs
5.0.2, 5.1.3, 5.2.2, 5.3.2, 5.4.2	❌ Failed: - Type 'Promise>>' is not assignable to type 'Promise>'. Type 'Map>' is not assignable to type 'Map'. Type 'Promise' is not assignable to type 'string'.