here's a cursed verification trace that fails:
```
thread 'main' panicked at netlist/src/design.rs:261:13:
verification failed!

design:
 %0:2 = input "i_insn"
 %2:2 = match %0:2 { 00 XX }
-%4:2 = match en=%2+0 %0+0 { X X }
+%4:2 = match en=%_8 %0+0 { X X }
-%6:2 = match en=%2+0 %0+0 { 0 0 }
+%6:2 = match en=%_8 %0+0 { 0 0 }
+%_8:1 = eq %0:2 00
+%_9:1 = eq %0:2 10
+%_10:1 = buf %0+0
+%_11:1 = or %_9 %_10
+%_12:1 = not %_8
+%_13:1 = buf %_8
+%_14:1 = eq { %0+0 %_8 } 01
+%_15:1 = eq { %0+0 %_8 } 11

counterexample:
%0:2 = 1X
%2:2 = 10
%4:2 = 00
%6:2 = 00
%_8 = 0
%_9 = X
%_10 = X
%_11 = X
%_12 = 1
%_13 = 0
%_14 = 0
%_15 = 0

possible cause: replacing net %2+1 with net %_11 is not valid
possible cause: replacing net %4+1 with net 0 is not valid
possible cause: replacing net %6+1 with net 0 is not valid
```