read_rtlil << EOT
module \top
   wire width 4 input 1 \a
   wire width 2 input 2 \b
   wire input 3 \clk
   wire width 4 output 4 \q
   wire input 5 \en
   wire width 4 \nq
   process \p
     assign \nq \a
     assign \nq [1:0] \b
     switch \en
       case 1'1
         assign \nq [3] 1'0
     end
     sync posedge \clk
       update \q \nq
   end
end
EOT
proc
check -assert