cleanup unused CBD code

Remove the check for CreateBeforeDestroyOverride which can't happen in a
destroy node.

Remove the unnecessary GraphNodeAttachDestroyer interface, since we
don't use it now that plans can record the create+destroy order.

terraform/node_resource_apply_instance.go

@@ -21,7 +21,6 @@ import (
 type NodeApplyableResourceInstance struct {
 	*NodeAbstractResourceInstance
 
-	destroyNode      GraphNodeDestroyerCBD
 	graphNodeDeposer // implementation of GraphNodeDeposerConfig
 
 	// If this node is forced to be CreateBeforeDestroy, we need to record that
@@ -39,13 +38,7 @@ var (
 	_ GraphNodeAttachDependencies = (*NodeApplyableResourceInstance)(nil)
 )
 
-// GraphNodeAttachDestroyer
-func (n *NodeApplyableResourceInstance) AttachDestroyNode(d GraphNodeDestroyerCBD) {
-	n.destroyNode = d
-}
-
-// CreateBeforeDestroy checks this nodes config status and the status af any
-// companion destroy node for CreateBeforeDestroy.
+// CreateBeforeDestroy returns this node's CreateBeforeDestroy status.
 func (n *NodeApplyableResourceInstance) CreateBeforeDestroy() bool {
 	if n.ForceCreateBeforeDestroy {
 		return n.ForceCreateBeforeDestroy
@@ -55,10 +48,6 @@ func (n *NodeApplyableResourceInstance) CreateBeforeDestroy() bool {
 		return n.Config.Managed.CreateBeforeDestroy
 	}
 
-	if n.destroyNode != nil {
-		return n.destroyNode.CreateBeforeDestroy()
-	}
-
 	return false
 }
 

terraform/node_resource_destroy.go

@@ -21,8 +21,6 @@ type NodeDestroyResourceInstance struct {
 	// this node destroys a deposed object of the associated instance
 	// rather than its current object.
 	DeposedKey states.DeposedKey
-
-	CreateBeforeDestroyOverride *bool
 }
 
 var (
@@ -63,10 +61,6 @@ func (n *NodeDestroyResourceInstance) CreateBeforeDestroy() bool {
 		}
 	}
 
-	if n.CreateBeforeDestroyOverride != nil {
-		return *n.CreateBeforeDestroyOverride
-	}
-
 	if n.Config != nil && n.Config.Managed != nil {
 		return n.Config.Managed.CreateBeforeDestroy
 	}
@@ -76,7 +70,6 @@ func (n *NodeDestroyResourceInstance) CreateBeforeDestroy() bool {
 
 // GraphNodeDestroyerCBD
 func (n *NodeDestroyResourceInstance) ModifyCreateBeforeDestroy(v bool) error {
-	n.CreateBeforeDestroyOverride = &v
 	return nil
 }
 

terraform/transform_destroy_cbd.go

@@ -23,20 +23,6 @@ type GraphNodeDestroyerCBD interface {
 	ModifyCreateBeforeDestroy(bool) error
 }
 
-// GraphNodeAttachDestroyer is implemented by applyable nodes that have a
-// companion destroy node. This allows the creation node to look up the status
-// of the destroy node and determine if it needs to depose the existing state,
-// or replace it.
-// If a node is not marked as create-before-destroy in the configuration, but a
-// dependency forces that status, only the destroy node will be aware of that
-// status.
-type GraphNodeAttachDestroyer interface {
-	// AttachDestroyNode takes a destroy node and saves a reference to that
-	// node in the receiver, so it can later check the status of
-	// CreateBeforeDestroy().
-	AttachDestroyNode(n GraphNodeDestroyerCBD)
-}
-
 // ForcedCBDTransformer detects when a particular CBD-able graph node has
 // dependencies with another that has create_before_destroy set that require
 // it to be forced on, and forces it on.

terraform/transform_destroy_edge.go

@@ -157,16 +157,6 @@ func (t *DestroyEdgeTransformer) Transform(g *Graph) error {
 				dag.VertexName(a), dag.VertexName(a_d))
 
 			g.Connect(dag.BasicEdge(a, a_d))
-
-			// Attach the destroy node to the creator
-			// There really shouldn't be more than one destroyer, but even if
-			// there are, any of them will represent the correct
-			// CreateBeforeDestroy status.
-			if n, ok := cn.(GraphNodeAttachDestroyer); ok {
-				if d, ok := d.(GraphNodeDestroyerCBD); ok {
-					n.AttachDestroyNode(d)
-				}
-			}
 		}
 	}