We were running Next's state constructors through the same validation of user-registered constructors, but that's inappropriate. It's OK for them to hold &mut references, since they might be needed later in the pipeline.
There was a bug in our code to determine which request scoped components should be built. The set of prebuilt ids didn't include components that might later become relevant because they are "passed through" without being touched.
Two issues combined:
Next
's state constructors through the same validation of user-registered constructors, but that's inappropriate. It's OK for them to hold &mut references, since they might be needed later in the pipeline.