Temporary structure used when parsing variable declarations.
(vl-vardeclassign-p x) is a defaggregate of the following fields.
Source link:
This captures something like a
variable_type ::= identifier { range } | identifier '=' expression
Or
variable_decl_assignment ::= identifier { variable_dimension } [ '=' expression ] | identifier unsized_dimension { variable_dimension } [ '=' dynamic_array_new ] | identifier [ '=' class_new ]