Well, this is a short test case :
kernel void k_test(out float4 bb<>, float4 aa<> ) {
int4 i2d = instance(bb);
bb=aa;
}
and the associated compiler error (coming from StreamKernelAnalyzer)
Line (9) : Error (parse error) before 'Identifier'
int4 i2d = instance(bb); ^
1 errors found.
***Unable to parse Line