I'm experiencing issues with duplicated Typescript type declarations in the following case:
I've got the following dependency tree for my application A:
A->@angular/http:2.3.1
A->B->@angular/http:2.3.1
Both A and B are managed by npm. After running
npm install
the filesystem looks like this:
A/node_modules/
@angular/http
...
B/node_modules
@angular/http
The problem seems to be that now there are two type declarations of @angular/http types like Response, or Headers. And somehow the Typescript transpiler seems unable to handle that - resulting in the following error message:
TS2453:The type argument for type parameter 'T' cannot be inferred from the usage. Consider specifying the type arguments explicitly. Type argument candidate 'Response' is not a valid type argument because it is not a supertype of candidate 'Response'. Types of property 'headers' are incompatible. Type 'Headers' is not assignable to type 'Headers'. Types have separate declarations of a private property 'mayBeSetNormalizedName'.
Reading the message, I guess this is a hickup of Typescript not being able to match the duplicated type declarations.
Anybody experienced the same issue? How to handle that problem? How to handle such name collisions?
Meanwhile I found out that you can fix this error by explicitly importing the according types inside the using class of A. In my case (cp. error message above), I needed to:
import {Response, Headers} from '@angular/http';
I had the same problem. There are basically two ways to solve this.
as any as TheRequiredObject see below.Let assume you got this class in project b:
export class B{
getSome(): Observable {
return this.http.get('some_url');
}
}
and this is what you want in project a:
export class A{
getSomeFromB: Observable{
return B.getSome() as any as Observable;
}
}