internal/core/adt: update environment for disjunctions

When passing tasks crossing disjunctions, we need
to update the corresponding Environments to reflect
the updated Vertex values. This was not done for
disjunctions. This meant that a disjunction within
a field that gets unified with another disjunction might
not resolve correctly.

This is fixed by simply updating the respective
Environment. The disjunction array was already copied
before, so this should not give significant performance
issues.

Fixes #3891

Signed-off-by: Marcel van Lohuizen <[email protected]>
Change-Id: I1dce73ae8f7491f446fe3a66d33388e578b6bf6c
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1214809
TryBot-Result: CUEcueckoo <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>

Author: mpvl

cue/testdata/eval/disjunctions.txtar

@@ -746,7 +746,7 @@ Result:
   }
   issue3891: (struct){
     reduced: (struct){
-      x: (_){ _ }
+      x: (_){ |(*(int){ 1 }, (_){ _ }) }
       a: ~(issue3891.reduced.b)
       b: (struct){
         y: (int){ 1 }
@@ -759,7 +759,7 @@ Result:
             sub2: (string){ "bar" }
           }
         }
-        foo: (_){ _ }
+        foo: (_){ |(*(string){ "bar" }, (_){ _ }) }
       }
       _transform: (struct){
         in: (_){ _ }
@@ -903,28 +903,17 @@ diff old new
            x: (bool){ true }
          }) }
        bar: (#struct){ |((#struct){
-@@ -436,10 +415,8 @@
-   }
+@@ -437,9 +416,7 @@
    issue3891: (struct){
      reduced: (struct){
--      x: (_){ |(*(int){ 1 }, (_){ _ }) }
+       x: (_){ |(*(int){ 1 }, (_){ _ }) }
 -      a: (struct){
 -        y: (int){ 1 }
 -      }
-+      x: (_){ _ }
 +      a: ~(issue3891.reduced.b)
        b: (struct){
          y: (int){ 1 }
        }
-@@ -451,7 +428,7 @@
-             sub2: (string){ "bar" }
-           }
-         }
--        foo: (_){ |(*(string){ "bar" }, (_){ _ }) }
-+        foo: (_){ _ }
-       }
-       _transform: (struct){
-         in: (_){ _ }
 @@ -475,14 +452,14 @@
      }
      full: (struct){

internal/core/adt/overlay.go

@@ -309,7 +309,10 @@ func (ctx *overlayContext) cloneNodeContext(n *nodeContext) *nodeContext {
 	if len(n.disjunctions) > 0 {
 		// Do not clone cc in disjunctions, as it is identified by underlying.
 		// We only need to clone the cc in disjunctCCs.
-		d.disjunctions = append(d.disjunctions, n.disjunctions...)
+		for _, x := range n.disjunctions {
+			x.env = ctx.derefDisjunctsEnv(x.env)
+			d.disjunctions = append(d.disjunctions, x)
+		}
 	}
 
 	return d