Use slang $info in a module to constant-fold 4-state SV expressions

To get a third opinion on SystemVerilog 4-state semantics without a simulator, put the operands in localparams and print the expression with an elaboration-time $info("%b", expr) directly in the module body, then run slang --quiet file.sv. slang's constant evaluator applies the LRM rules, e.g. {3{1'bz}} == 3'b001 gives x. Include a known-0/1 control line so you can tell real folding from a pattern that never matched. It only covers constant operands: control flow, flops and dump-dependent behaviour still need a 4-state simulator such as Icarus (iverilog -g2012). Verilator can't help there, since it's 2-state and turns x/z into 0.