internal/core/adt: eliminate non-rooted indirections

Resolve now always derefences Vertex values that
do not contribute valuable information. This is also
the right granularity needed for the old evaluator, so
we make the change for both, simplifying the code.

We also remove the indirection in dep, which is now
no longer needed.

We could have merged this CL with the change in dep,
but we keep it as a separate CL so that if this change
causes issues, it can be safely rolled back without
compromising the fix in dep.

Issue #3060

Signed-off-by: Marcel van Lohuizen <[email protected]>
Change-Id: Iba414b9d1db6479274fe5b80574ae9704e4b0f6f
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1194446
TryBot-Result: CUEcueckoo <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>

internal/core/adt/context.go

@@ -496,9 +496,9 @@ func (c *OpContext) resolveState(x Conjunct, r Resolver, state combinedFlags) (*
 		return nil, arc.ChildErrors
 	}
 
-	if !c.isDevVersion() {
-		arc = arc.DerefValue()
-	}
+	// Dereference any vertices that do not contribute to more knownledge about
+	// the node.
+	arc = arc.DerefNonRooted()
 
 	return arc, err
 }

internal/core/dep/dep.go

@@ -461,7 +461,7 @@ func (c *visitor) reportDependency(env *adt.Environment, ref adt.Resolver, v *ad
 	c.numRefs++
 
 	d := Dependency{
-		Node:      v.DerefNonRooted(),
+		Node:      v,
 		Reference: altRef,
 		pkg:       c.pkg,
 		top:       c.top,