Hoist slow binops incorrectly hoists

[rachitnigam]

The following program with --lower flag does not typecheck:

decl q: ubit<32>[20][20];
let q_i_j_1 = q[0][1];
---
q[1][0] := (((0-1) * 1 + (2*2) * 2 - 1*1 - 1*2) as ubit<32>);