internal/core/adt: dereference disjunct result

With nested disjunctions, disjuncts may end
up forwarded in Vertex.BaseValue in intermediate
results. This causes closeContext.arcs and Arcs
to be misaligned if these results are used in
further processing.

This is the case, for instance in the following
example:

{#v: 1} | 2
{#v: 1} | (2 | 3)
{#v: 1} | 2
{#v: 1} | 2

This issue led to duplicate disjuncts and many
other problems. The EvalAlpha test runs over
10% faster as a result of this change!

The test in conjuncts.txtar removes a spurious
element and is now correct.

The tests for 3528 were already fixed by an
earlier CL. We will leave the closing here,
though, to signal these changes are related.

Fixes #3528

Signed-off-by: Marcel van Lohuizen <mpvl@gmail.com>
Change-Id: Ieaeba4b758006592b115240dac2e29b967103c5a
Dispatch-Trailer: {"type":"trybot","CL":1206178,"patchset":3,"ref":"refs/changes/78/1206178/3","targetBranch":"master"}

cue/testdata/eval/conjuncts.txtar

@@ -69,15 +69,15 @@ issue2355: {
 }
 
 -- out/evalalpha/stats --
-Leaks:  187
-Freed:  25
-Reused: 25
-Allocs: 187
+Leaks:  216
+Freed:  30
+Reused: 30
+Allocs: 216
 Retain: 0
 
 Unifications: 43
-Conjuncts:    350
-Disjuncts:    124
+Conjuncts:    378
+Disjuncts:    152
 -- out/evalalpha --
 Errors:
 param: conflicting values "foo" and [{}] (mismatched types string and list):
@@ -102,7 +102,7 @@ Result:
         string
         #early: (string){ |(*(string){ "X" }, (string){ string }) }
       }) }
-    t3: (string){ |(*(string){ "X" }, (string){
+    t3: (string){ |(*(string){
         "X"
         #early: (string){ |(*(string){ "X" }, (string){ string }) }
       }, (string){
@@ -163,18 +163,18 @@ diff old new
 -Reused: 59
 -Allocs: 18
 -Retain: 22
-+Leaks:  187
-+Freed:  25
-+Reused: 25
-+Allocs: 187
++Leaks:  216
++Freed:  30
++Reused: 30
++Allocs: 216
 +Retain: 0
 
 -Unifications: 45
 -Conjuncts:    135
 -Disjuncts:    86
 +Unifications: 43
-+Conjuncts:    350
-+Disjuncts:    124
++Conjuncts:    378
++Disjuncts:    152
 -- diff/-out/evalalpha<==>+out/eval --
 diff old new
 --- old
@@ -200,7 +200,7 @@ diff old new
 -      //     ./in.cue:15:2
 -      #early: (string){ |(*(string){ "X" }, (string){ string }) }
 -    }
-+    t3: (string){ |(*(string){ "X" }, (string){
++    t3: (string){ |(*(string){
 +        "X"
 +        #early: (string){ |(*(string){ "X" }, (string){ string }) }
 +      }, (string){

internal/core/adt/disjunct2.go

@@ -451,6 +451,8 @@ func (n *nodeContext) doDisjunct(c Conjunct, m defaultMode, mode runMode) (*node
 		return nil, err
 	}
 
+	d = d.node.DerefDisjunct().state
+
 	return d, nil
 }
 

internal/core/adt/eval_test.go

@@ -88,7 +88,7 @@ var skipDebugDepErrors = map[string]int{
 	"disjunctions/edge":        1,
 	"disjunctions/elimination": 11,
 	"disjunctions/embed":       6,
-	"eval/conjuncts":           4,
+	"eval/conjuncts":           3,
 	"eval/notify":              17,
 	"fulleval/054_issue312":    1,
 	"scalars/embed":            1,