no near

d2compiler/compile.go

@@ -678,6 +678,10 @@ func (c *compiler) validateNear(g *d2graph.Graph) {
 					c.errorf(obj.Attributes.NearKey, "near keys cannot be set to an descendant")
 					continue
 				}
+				if nearObj.OuterSequenceDiagram() != nil {
+					c.errorf(obj.Attributes.NearKey, "near keys cannot be set to an object within sequence diagrams")
+					continue
+				}
 			} else if isConst {
 				is := false
 				for _, e := range g.Edges {

d2compiler/compile_test.go

@@ -1774,6 +1774,17 @@ dst.id <-> src.dst_id
 				assert.String(t, "sequence_diagram", g.Objects[0].Attributes.Shape.Value)
 			},
 		},
+		{
+			name: "near_sequence",
+
+			text: `x: {
+  shape: sequence_diagram
+  a
+}
+b.near: x.a
+`,
+			expErr: `d2/testdata/d2compiler/TestCompile/near_sequence.d2:5:9: near keys cannot be set to an object within sequence diagrams`,
+		},
 		{
 			name: "sequence-timestamp",