Synopsis A type other than void is needed.
Description This error is generated when a non-void value is needed, but only void is provided. The most prominent examples are splicing for Rascal:List, Rascal:Set, and Rascal:Map.

Remedy: replace the expression that computes void by an expression that computes a non-void value.
Examples First define a dummy function that returns void:
rascal>void dummy() { return; }
void (): void dummy();
rascal>[1, *dummy(), 2]
|stdin:///|(4,8,<1,4>,<1,12>): Non-void type required
rascal>{1, *dummy(), 2}
|stdin:///|(5,7,<1,5>,<1,12>): Non-void type required
A solution could be:
rascal>int dummy() { return 17; }
int (): int dummy();
rascal>[1, *dummy(), 2]
list[int]: [1,17,2]
rascal>{1, *dummy(), 2}
set[int]: {1,2,17}
Is this page unclear, or have you spotted an error? Please add a comment below and help us to improve it. For all other questions and remarks, visit