Field input nodes evaluate in a context, but currently they give no warning if they do not support
a particular context. The initial goal is to add a warning like "Input node does not support geometry type: Mesh" on the spline parameter node in the following situation:

Implementation

A potential implementation isn't clear.
It seems there needs to be a way to keep track of which node (bNode, NodeRef, DNode, etc.) the field input node came from.
Then the field evaluation system should have a way to collect errors and return them to the caller. Or maybe the caller can pass a
"logger" class to the field evaluation system. That generalization could allow more specific breakdowns of node timing in the future.