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Using an interface for two imports causes an error #529
Description
interface iface {
f: func()
}
default world w {
import p1: self.iface
import p2: self.iface
}This produces the following error:
$ wit-bindgen markdown example.wit
Error: interface `p2` imported more than once
--> example.wit:7:9
|
7 | import p2: self.iface
|
Is it actually not allowed to have two imports with the same interface? That seems surprising to me.
Activity
alexcrichton commentedon Mar 6, 2023
This is currently intended, yes, although perhaps not with the best error message. Additionally the specification for
WIT.mdin thecomponent-modelrepository should probably have more words about this. @lukewagner would be able to explain in more detail where this restriction comes from.surma commentedon Mar 6, 2023
Interesting! Yeah I’d love to hear more context. It’s especially confusing because it works just fine™️ if you spell out the interfaces:
lukewagner commentedon Mar 6, 2023
The basic idea (described more here) is that each import/export name has two parts, a developer-facing kebab-case string (meant to be converted into source-code bindings) and an optional
(id <URL>)field which, when present, is meant to uniquely identify the (standards- or vendor-defined) interface that is being requested/implemented. Theidis supposed to uniquely determine what is being requested, so that two imports of the sameidcan always be de-duplicated. But if a component can import the sameidtwice, that would imply that extra context is being used to identify the interface and thus duplicate imports/exports of the sameidis disallowed. In your first example,self.ifaceturned into anid, hence the duplicate error, while, in the second example, because the interfaces are anonymous/inline, there is noid.A better error message could help of course, but I do wonder if we should make it more explicit when an import/export includes an
idor not.