Expand IRI in object position

[multimeric]

I'm working with SHACL where sh:class expects the IRI of a class. Therefore, I want sh:class to behave with the same magic properties as @type, so that it always treats its object as an IRI, and always expands it. The goal is to be able to do {"class": "Foo"} in the actual graph, with whatever @context hacks are necessary. I'm finding this very difficult however. Can anyone suggest a solution?

My attempts are below.

---

First I try just marking class as taking an IRI, but this doesn't expand Foo:

{
  "@context": {
    "Foo": "https://example.org/Foo",
    "class": {"@type": "@id", "@id": "http://www.w3.org/ns/shacl#Class"}
  },
  "class": "Foo"
}

{
  "http://www.w3.org/ns/shacl#Class": { "@id": "Foo" }
}

---

Trying to play with Foo's own @type has no effect, e.g.

{
  "@context": {
    "Foo": {"@type": "@id", "@id": "https://example.org/Foo"},
    "class": {"@type": "@id", "@id": "http://www.w3.org/ns/shacl#Class"}
  },
  "class": "Foo"
}

Or

{
  "@context": {
    "Foo": {"@type": "@vocab", "@id": "https://example.org/Foo"},
    "class": {"@type": "@id", "@id": "http://www.w3.org/ns/shacl#Class"}
  },
  "class": "Foo"
}

---

The only hacky workaround I can find is to mark Foo as a prefix and then also add a colon (which I don't want):

{
  "@context": {
    "Foo": {"@prefix": true, "@id": "https://example.org/Foo"},
    "class": {"@type": "@id", "@id": "http://www.w3.org/ns/shacl#Class"}
  },
  "class": "Foo:"
}

{
  "http://www.w3.org/ns/shacl#Class": {
    "@id": "https://example.org/Foo"
  }
}