add an interp that fails during planned destroy

Chain some values so that we can get an interpolation that fails if a
module input is evaluated during destroy.

terraform/context_apply_test.go

@@ -10521,7 +10521,6 @@ func TestContext2Apply_plannedDestroyInterpolatedCount(t *testing.T) {
 	}
 
 	ctxOpts.ProviderResolver = providerResolver
-	ctxOpts.Destroy = true
 	ctx, diags = NewContext(ctxOpts)
 	if diags.HasErrors() {
 		t.Fatalf("err: %s", diags.Err())

terraform/testdata/plan-destroy-interpolated-count/main.tf

@@ -3,9 +3,18 @@ variable "list" {
 }
 
 resource "aws_instance" "a" {
-  count = "${length(var.list)}"
+  count = length(var.list)
+}
+
+locals {
+  ids = aws_instance.a[*].id
+}
+
+module "empty" {
+  source = "./mod"
+  input = zipmap(var.list, local.ids)
 }
 
 output "out" {
-  value = "${aws_instance.a.*.id}"
+  value = aws_instance.a[*].id
 }

terraform/testdata/plan-destroy-interpolated-count/mod/main.tf

@@ -0,0 +1,2 @@
+variable "input" {
+}