Optimisations to do

[L-as]

• Case of known constructors
  • Let-bind if term is used more than once
  • Otherwise inline
• η-reduction (for all types)
• Merging matches on same thing (choose the top-most one)
• User-defined rewrite rules (not through RULES pragma) (hard)
• Common Expression Elimination (not subexpression elimination) / hoisting
• Detect partial updating with pcon and pmatch/pcase