update validation and test

d2compiler/compile.go

@@ -1083,6 +1083,14 @@ func (c *compiler) validateNear(g *d2graph.Graph) {
 		if (isSrcNearConst || isDstNearConst) && srcNearContainer != dstNearContainer {
 			// c.errorf(edge.References[0].Edge, "cannot connect objects from within a container, that has near constant set, to objects outside that container")
 		}
+		if edge.Src.IsConstantNear() && edge.Dst.IsDescendantOf(edge.Src) {
+			c.errorf(edge.GetAstEdge(), "edge from constant near %#v cannot enter itself", edge.Src.AbsID())
+			continue
+		}
+		if edge.Dst.IsConstantNear() && edge.Src.IsDescendantOf(edge.Dst) {
+			c.errorf(edge.GetAstEdge(), "edge from constant near %#v cannot enter itself", edge.Dst.AbsID())
+			continue
+		}
 	}
 
 }

d2graph/d2graph.go

@@ -1226,7 +1226,7 @@ func (obj *Object) Connect(srcID, dstID []string, srcArrow, dstArrow bool, label
 	dst := obj.ensureChildEdge(dstID)
 
 	if src.OuterSequenceDiagram() != dst.OuterSequenceDiagram() {
-		return nil, errors.New("connections within sequence diagrams can connect only to other objects within the same sequence diagram")
+		// return nil, errors.New("connections within sequence diagrams can connect only to other objects within the same sequence diagram")
 	}
 
 	e := &Edge{

e2etests/testdata/files/nesting_power.d2

@@ -24,7 +24,7 @@ l: Left Constant Near {
     grid: {
       shape: sequence_diagram
 
-      with -> a -> sequence diagram -> you can
+      with -> a -> sequence diagram.x -> you can
 
       you can: {
         grid-rows: 2
@@ -45,6 +45,7 @@ l: Left Constant Near {
           continue -> nesting
         }
       }
+      you can.here and.nesting -> sequence diagram.x: {class: green}
     }
     this.row 2 -> is.child of is.grandchild: {class: green}
     # this.row 2 -> grid.you can
@@ -246,6 +247,9 @@ more: {
 more.container.a_sequence -> directions.v.d.4: {class: green}
 directions.l.2 -> center.step: {class: green}
 center.step -> more.stylish.x: {class: green}
+directions.l.1 -> seq.item.a.b: to inside sequence diagram {class: green}
+directions.l.1 -> seq.itemResponse.a: to inside sequence diagram {class: green}
+directions.v.d.2 -> seq.scorer.abc: to inside sequence diagram {class: green}
 
 center.cloud -> more.stylish: {class: green}
 more.container.a_shape -> r.is: to constant near {class: green}