Multiple meanings for `(instance`.

[sunfishcode]

In the explainer:

componentarg ::= (module <moduleidx>)
               | (component <componentidx>)
               | (instance <instanceidx>)
               | (func <funcidx>)
               | (value <valueidx>)
               | (type <typeidx>)
               | (instance <export>*)

Would it make sense to rename the second instance to exports, or something, to make it clear that it's a distinct construct doing a specific thing, and make it easier to make correspondences between code and documentation?

[Updated to reflect the latest updates]

[lukewagner]

If this poses a serious parsing challenge or it's confusing to folks, I'd be open to changing it but what I think is nice about the current syntax is that we're always passing an instance argument for an instance import, so the two line up clearly. My impression is that the first few tokens of <instanceidx> and <export>* would be sufficiently different to distinguish the two without too much trouble.

[guybedford]

Would renaming (instance <export>*) to (namespace <export>*) be another possible option here? Like importing module namespaces in ESM. That might also more clearly disambiguate the ESM integration since this is the only case when importing in the ESM integration where the default is not taken off the namespace (import { default as Foo } from "./foo.wasm" as "wasm-module", the current module type analog being an effective default).

[lukewagner]

We talked about this topic a bit more in this comment thread and IRL and the conclusion here I think is that instances are fundamentally immutable record values composed of name:value pairs. Thus, I think (instance (export "a" (func $a)) (export "b" (func $b))) is the natural constructor syntax for these instance values and not a separate thing that needs a distinct name.

[guybedford]

Ok, makes sense!

instances are fundamentally immutable record values composed of name:value pairs

I suggested the term "namespace" because that is pretty much the definition of a JS module namespace exotic object too.

[sunfishcode]

Thinking about this more, part of my confusion here arises from the underlying situation that the same (instance ...)-style syntax is used for instance definitions, instance references, and instance types. That largely comes from the core-wasm S-expression format though,

[sunfishcode]

and changing that would risk creating more confusion at this point.