bindnode cannot infer schemas with links

[aschmahmann]

bindnode currently cannot infer schemas with links in them such as:

type Node struct {
   Next cidlink.Link
}

next := &Node{ Next: nextCid }
node := bindnode.Wrap(next, nil)

It will error with:

panic: duplicate type name: Link [recovered]
	panic: duplicate type name: Link

goroutine 55 [running]:
testing.tRunner.func1.2({0x18ccd60, 0xc000095f20})
	C:/Go/go1.17.5/src/testing/testing.go:1209 +0x24e
testing.tRunner.func1()
	C:/Go/go1.17.5/src/testing/testing.go:1212 +0x218
panic({0x18ccd60, 0xc000095f20})
	C:/Go/go1.17.5/src/runtime/panic.go:1038 +0x215
github.com/ipld/go-ipld-prime/schema.(*TypeSystem).Accumulate(0x28424e0, {0x1e4c498, 0xc0000a4be0})
	C:/Users/adin/go/pkg/mod/github.com/ipld/go-ipld-prime@v0.14.4-0.20211217152141-008fd70fc96f/schema/tmpBuilders.go:151 +0x1b4
github.com/ipld/go-ipld-prime/node/bindnode.inferSchema({0x1e6db40, 0x1a3a1c0})
	C:/Users/adin/go/pkg/mod/github.com/ipld/go-ipld-prime@v0.14.4-0.20211217152141-008fd70fc96f/node/bindnode/infer.go:318 +0x5f3
github.com/ipld/go-ipld-prime/node/bindnode.inferSchema({0x1e6db40, 0x1996140})
	C:/Users/adin/go/pkg/mod/github.com/ipld/go-ipld-prime@v0.14.4-0.20211217152141-008fd70fc96f/node/bindnode/infer.go:303 +0x468
github.com/ipld/go-ipld-prime/node/bindnode.Wrap({0x189f960, 0xc000258090}, {0x0, 0x0})
	C:/Users/adin/go/pkg/mod/github.com/ipld/go-ipld-prime@v0.14.4-0.20211217152141-008fd70fc96f/node/bindnode/api.go:79 +0x1d9
...

What's going on is that inferSchema

go-ipld-prime/node/bindnode/infer.go

Line 288 in 008fd70

func inferSchema(typ reflect.Type) schema.Type {

doesn't have any concept of Links.

We do have some types predefined already for what a Link could reasonably be, although we can also try interface detection to see if something fulfills the interface for an IPLD link. The ones we already have defined are

go-ipld-prime/node/bindnode/infer.go

Lines 20 to 22 in 008fd70

	goTypeLink = reflect.TypeOf((*datamodel.Link)(nil)).Elem()
	goTypeCidLink = reflect.TypeOf((*cidlink.Link)(nil)).Elem()
	goTypeCid = reflect.TypeOf((*cid.Cid)(nil)).Elem()

[mvdan]

Thanks for reporting - I'll fix this soon.