Jakob Schneider

RFR (modulo the debug statements)

I have made the `isSubset` predicate recursively defined which holds in the case for concrete types but not for polymorphic return types. Intuitively it should hold that if "you can...

> Can both of you also take a look at `Scheme.lessThanEqual` and tell me if it is relevant/related. It seems relevant. IIRC, we used `Scheme.equal` in the last prototype, so...

The current version implements exactly the relation in the paper. It seems, however, that we *should* be able to use `Scheme.leq` for the effect subset check. That would hopefully also...

Should we add the ignored tests as negative tests? This version intentionally does not handle changes in the parameters (in the subset relation).

I think so yes. One nitpick: We should not call it `merkleHash` but something more appropriate like `treeHash` since it's not entirely a Merkle-Damgård hash.

> What if you change it while the compiler is not running? I.e. between two separate invocations? Remove the libraries that are not in the dependency graph (after dependency resolution)

- [x] `visitSelectRule` line 1913 ```scala private def visitSelectRule(tree: Tree): Validation[SelectChannelRule, CompilationMessage] = { expect(tree, TreeKind.Expr.SelectRuleFragment) val exprs = traverse(pickAll(TreeKind.Expr.Expr, tree))(visitExpr) flatMapN(pickNameIdent(tree), exprs) { case (ident, channel :: body ::...

For `pick` do we have an empty tree node?

> I think the JvmOp stuff is deprecated -- so that one could be become an ICE because it will be removed soon anyway. What about this comment? ``` //...