User reported trying to use a Vector Parameter with a Custom Expression and the parameter was only registered as a Float3 and would give the X3017 error when compiling.
I confirmed this and tested the same node with a component mask set to RGBA and again the Material Editor threw a warning about not enough arguments from Parameter (float3) to mask.
Constant4 Vector works without error in both cases.
This is contradictory to documentation which says that "The VectorParameter expression is identical to the Constant4Vector"
RESULTS: Error regarding arguments in Vector Parameter
EXPECTED: Vector Parameter to retain a 4 vector output and no errors generated.
Head over to the existing Questions & Answers thread and let us know what's up.