internal/core/adt: fix Definition closedness bug in API

Open structs or structs with ellipsis should always allow
fields, not just regular ones.
The question is if this is really the case when we disallow
definitions in closed struct by default, but it seems fair
enough to allow this until this is the case as it is consistent
with CUE's behavior.

Fixes #2320
Issue #543

Signed-off-by: Marcel van Lohuizen <mpvl@gmail.com>
Change-Id: I25a42948f569e81ddacc74c7467c98a287861bea
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/552331
Unity-Result: CUEcueckoo <cueckoo@cuelang.org>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Reviewed-by: Roger Peppe <rogpeppe@gmail.com>

cue/types_test.go

@@ -31,6 +31,8 @@ import (
 	"cuelang.org/go/internal/astinternal"
 	"cuelang.org/go/internal/core/adt"
 	"cuelang.org/go/internal/core/debug"
+	"cuelang.org/go/internal/cuetest"
+	"cuelang.org/go/internal/tdtest"
 )
 
 func getInstance(t *testing.T, body string) *Instance {
@@ -2111,12 +2113,13 @@ func TestSubsumes(t *testing.T) {
 func TestUnify(t *testing.T) {
 	a := "a"
 	b := "b"
-	testCases := []struct {
+	type testCase struct {
 		value string
 		pathA string
 		pathB string
 		want  string
-	}{{
+	}
+	testCases := []testCase{{
 		value: `4`,
 		want:  `4`,
 	}, {
@@ -2156,21 +2159,26 @@ func TestUnify(t *testing.T) {
 		pathA: "#T",
 		pathB: b,
 		want:  `{}`,
+	}, {
+		value: `
+		a: #A: "foo"
+		#B: {...}
+		`,
+		pathA: a,
+		pathB: "#B",
+		want:  `{}`,
 	}}
-	for _, tc := range testCases {
-		t.Run(tc.value, func(t *testing.T) {
-			v := getInstance(t, tc.value).Value()
-			x := v.LookupPath(ParsePath(tc.pathA))
-			y := v.LookupPath(ParsePath(tc.pathB))
-			b, err := x.Unify(y).MarshalJSON()
-			if err != nil {
-				t.Fatal(err)
-			}
-			if got := string(b); got != tc.want {
-				t.Errorf("got %v; want %v", got, tc.want)
-			}
-		})
-	}
+	// TODO(tdtest): use cuetest.Run when supported.
+	tdtest.Run(t, testCases, func(t *cuetest.T, tc *testCase) {
+		v := getInstance(t.T, tc.value).Value()
+		x := v.LookupPath(ParsePath(tc.pathA))
+		y := v.LookupPath(ParsePath(tc.pathB))
+		b, err := x.Unify(y).MarshalJSON()
+		if err != nil {
+			t.Fatal(err)
+		}
+		t.Equal(string(b), tc.want)
+	})
 }
 
 func TestEquals(t *testing.T) {

internal/core/adt/closed.go

@@ -480,7 +480,7 @@ func verifyArc(ctx *OpContext, s *StructInfo, f Feature, label Value) bool {
 	o := s.StructLit
 	env := s.Env
 
-	if isRegular && (len(o.Additional) > 0 || o.IsOpen) {
+	if len(o.Additional) > 0 || o.IsOpen {
 		return true
 	}