[1.3.*] Types of parameters '__0' and 'value' are incompatible.

Bug Report

- [x] bug report
- [ ] feature request

Versions.

@typescript: 2.4.2
@rxjs: 5.4.3
@angular/cli: 1.3.1
node: 8.0.0
os: linux x64
@angular/animations: 4.3.4
@angular/cdk: 2.0.0-beta.8
@angular/common: 4.3.4
@angular/compiler: 4.3.4
@angular/core: 4.3.4
@angular/flex-layout: 2.0.0-beta.8
@angular/forms: 4.3.4
@angular/http: 4.3.4
@angular/material: 2.0.0-beta.8
@angular/platform-browser: 4.3.4
@angular/platform-browser-dynamic: 4.3.4
@angular/router: 4.3.4
@angular/cli: 1.3.1
@angular/compiler-cli: 4.3.4

Repro steps.

    let s: string = 'abc',
        b: boolean = true,
        n: number = 10;

    Observable.forkJoin([Observable.of(s), Observable.of(b), Observable.of(n)])
        .map(([s, b, n]: [string, boolean, number]) => s);

The log given by the failure.

ERROR in file.ts (6,18): Argument of type '([s, b, n]: [string, boolean, number]) => string' is not assignable to parameter of type '(value: boolean[], index: number) => string'.
  Types of parameters '__0' and 'value' are incompatible.
    Type 'boolean[]' is not assignable to type '[string, boolean, number]'.
      Property '0' is missing in type 'boolean[]'.

Desired functionality.

This code gets compiled on v1.2.7 but fails on v1.3.*

[karser]

Thanks @clydin. There are 3 working examples that get compiled under angular-cli 1.3.1 and TS 2.4:

1. cast the array parameter as any[]

Observable.forkJoin([Observable.of(s), Observable.of(n)])
    .map(([s, n]: any[]) => s);

1. surprisingly, I found out that if I pass observables into forkJoin not as an array but as a function arguments, the error disappears, so my original example works:

Observable.forkJoin(Observable.of(s), Observable.of(n))
    .map(([s, n]: [string, number]) => s);

1. manually define the generic type parameter on forkJoin.

Observable.forkJoin<string,number>(Observable.of(s), Observable.of(n))
    .map(([s, n]) => s);

[karser]

@clydin Could you please provide some reference that forkJoin doesn't work with a multi-type array in TS 2.4? Is it by design? What would be a solution in this case? In this example forkJoin accepts observables of multiple types. I removed all the type casts from my previous code but I’m getting ERROR in file.ts (5,38): Argument of type 'string' is not assignable to parameter of type 'number'.:

let s: string = 'abc',
    n: number = 10;

Observable.forkJoin([Observable.of(s), Observable.of(n)])
    .map(responses => takesB(responses[1]));

function takesB(n: number) {
}