internal/core/adt: also check closedness for list in Equal

Without this check, open lists will be considered to be
identical to closed lists. This, in turn, could lead to one
of such cases to be eliminated from a disjunction.

E.g. closed([]) | [] should not be simplified to closed([]).

Issue #2884

Signed-off-by: Marcel van Lohuizen <mpvl@gmail.com>
Change-Id: I3e410c651729d0883809c83d20a980794d278e5f
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1191574
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>

cue/testdata/comprehensions/issue507.txtar

@@ -33,42 +33,6 @@ Retain: 0
 Unifications: 11
 Conjuncts:    17
 Disjuncts:    15
--- out/evalalpha --
-(struct){
-  somelist: (list){
-  }
-  foo: (#list){
-  }
-  otherlist: (#list){
-    0: (string){ "something" }
-  }
-  z: (#list){
-    0: (string){ "hello z: something" }
-  }
-  extlist: (list){ |(*(#list){
-      0: (string){ "something" }
-    }, (list){
-    }) }
-  bar: (#list){
-    0: (string){ "hello bar: something" }
-  }
-}
--- diff/-out/evalalpha<==>+out/eval --
-diff old new
---- old
-+++ new
-@@ -1,7 +1,6 @@
- (struct){
--  somelist: (list){ |(*(#list){
--    }, (list){
--    }) }
-+  somelist: (list){
-+  }
-   foo: (#list){
-   }
-   otherlist: (#list){
--- diff/todo/p0 --
-somelist: Dropped disjunction
 -- out/eval --
 (struct){
   somelist: (list){ |(*(#list){

cue/testdata/fulleval/027_len_of_incomplete_types.txtar

@@ -42,46 +42,6 @@ Retain: 3
 Unifications: 59
 Conjuncts:    105
 Disjuncts:    93
--- out/evalalpha --
-(struct){
-  args: (#list){
-  }
-  v1: (int){ 0 }
-  v2: (int){ 0 }
-  v3: (int){ 0 }
-  v4: (int){ 1 }
-  v5: (_|_){
-    // [incomplete] v5: unresolved disjunction {a:3} | {a:4} (type struct):
-    //     ./in.cue:6:7
-  }
-  v6: (_|_){
-    // [incomplete] v6: unresolved disjunction 'sf' | 'dd' (type bytes):
-    //     ./in.cue:7:7
-  }
-  v7: (int){ 2 }
-  v8: (_|_){
-    // [incomplete] v8: unresolved disjunction [2] | [1,2] (type list):
-    //     ./in.cue:9:7
-  }
-  v9: (int){ 4 }
-  v10: (int){ 0 }
-}
--- diff/-out/evalalpha<==>+out/eval --
-diff old new
---- old
-+++ new
-@@ -1,7 +1,6 @@
- (struct){
--  args: (list){ |(*(#list){
--    }, (list){
--    }) }
-+  args: (#list){
-+  }
-   v1: (int){ 0 }
-   v2: (int){ 0 }
-   v3: (int){ 0 }
--- diff/todo/p0 --
-Incorrectly chosen default.
 -- out/eval --
 (struct){
   args: (list){ |(*(#list){

internal/core/adt/equality.go

@@ -67,6 +67,9 @@ func equalVertex(ctx *OpContext, x *Vertex, v Value, flags Flag) bool {
 		if x.IsClosedStruct() != y.IsClosedStruct() {
 			return false
 		}
+		if x.IsClosedList() != y.IsClosedList() {
+			return false
+		}
 		if !equalClosed(ctx, x, y, flags) {
 			return false
 		}