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The above does not raise a type error. test.getWriter().write({ a: "string" }) will not show an error, even though the underlying stream expects b properties on the chunks. A variation of the problem is this:
constwritable=newWritableStream<{a: string;b: string}>();newReadableStream<{a: string}>().pipeTo(writable);// No error
WritableStream<A> and WritableStream<B> differ in the signature of their getWriter().write(chunk) method. Because WritableStreamDefaultWriter.write(chunk) is a method, it is bivariant, leading to the above examples to pass.
Other than for example Array, WritableStream is only ever used for writing, never for reading, so as far as my understanding goes, bivariance does not have any use here. This is why I would suggest to change the typing of WritableStream to make it contravariant, to make the examples above raise errors. One way to achieve that would be to declare WritableStreamDefaultWriter.write() as a function property instead of a method, that would solve the problem at least in strict mode:
write: (chunk?: W)=>Promise<void>;
Although I am not sure whether that would have any other implications.
As a workaround, I use the following code:
constwrite=Symbol();declare global {interfaceWritableStreamDefaultWriter<W=any>{[write]: (a: W)=>void;}}
Some more details about this can also be found on StackOverflow.
### Documentation Link
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The text was updated successfully, but these errors were encountered:
⚙ Compilation target
esnext
⚙ Library
dom
Missing / Incorrect Definition
WritableStreamDefaultWriter.write(chunk)
Sample Code
The above does not raise a type error.
test.getWriter().write({ a: "string" })
will not show an error, even though the underlying stream expectsb
properties on the chunks. A variation of the problem is this:WritableStream<A>
andWritableStream<B>
differ in the signature of theirgetWriter().write(chunk)
method. BecauseWritableStreamDefaultWriter.write(chunk)
is a method, it is bivariant, leading to the above examples to pass.Other than for example
Array
,WritableStream
is only ever used for writing, never for reading, so as far as my understanding goes, bivariance does not have any use here. This is why I would suggest to change the typing ofWritableStream
to make it contravariant, to make the examples above raise errors. One way to achieve that would be to declareWritableStreamDefaultWriter.write()
as a function property instead of a method, that would solve the problem at least in strict mode:Although I am not sure whether that would have any other implications.
As a workaround, I use the following code:
Some more details about this can also be found on StackOverflow.
The text was updated successfully, but these errors were encountered: