ID:10464 VHDL Unsupported Feature error at <location>: can't declare signals with unconstrained scalar or array type

CAUSE: In a signal declaration at the specified location in a VHDL Design File (.vhd), you declared a signal with an unconstrained scalar or array type. A unconstrained scalar type has an undefined range (no fixed bounds or direction) as indicated by the box (<>) symbol. An unconstrained array type has an undefined index range, also indicated by the box symbol. Quartus Prime Integrated Synthesis does not support signals with unconstrained types.

ACTION: Declare the signal with a constrained type, or specify a defined range constraint after the type name in the signal declaration's subtype indication.