Reproduces on latest master (f69c63c668)

Repro steps:

1. Create a new Unlit shader
2. Create a custom function node, with an input "In" and an output "Out"
3. Make the body of the custom function node "Out = In;" (no quotes)
4. Plug a vector1 node into the "In" input
5. Right click the edge between the two nodes and add a redirect node
Expected result: no error
Actual result: the custom function node errors (see comment for error)