message: `const IRInstruction*` for key of type environments
diff: @@ -189,7 +189,8 @@ class TypeInference final
  void traceState(TypeEnvironment* state) const;
  - std::unordered_map<IRInstruction*, TypeEnvironment>& get_type_environments() {
  + std::unordered_map<const IRInstruction*, TypeEnvironment>&
  + get_type_environments() {
  return m_type_envs;
  }
  @@ -197,7 +198,7 @@ class TypeInference final
  void populate_type_environments();
  const cfg::ControlFlowGraph& m_cfg;
  - std::unordered_map<IRInstruction*, TypeEnvironment> m_type_envs;
  + std::unordered_map<const IRInstruction*, TypeEnvironment> m_type_envs;
  TypeDomain refine_type(const TypeDomain& type,
  IRType expected,
  