Consider the following test case:
module issue_042(y); output [3:0] y; localparam [3:0] p11 = 1'bx; assign y = ~&p11; endmodule
Quartus 15.0 sets y to constant 4'b0000. The correct value for y would be 4'b0001.
Crosscheck: Vivado 2015.1, XSim 2015.1, Modelsim 10.3d, Icarus Verilog (git 02ee387), and Verilator (git e5af46d) all agree on the correct behavior.
History:
2015-05-15 Reported via Altera mySupport (SR #11146970)
2017-07-01 Still broken in Quartus II 17.0