diff --git a/code/compiler/13/ast.cpp b/code/compiler/13/ast.cpp
index 7efe9b1..1f1eb31 100644
--- a/code/compiler/13/ast.cpp
+++ b/code/compiler/13/ast.cpp
@@ -3,6 +3,7 @@
 #include <type_traits>
 #include "binop.hpp"
 #include "error.hpp"
+#include "type.hpp"
 #include "type_env.hpp"
 #include "env.hpp"
 
@@ -275,9 +276,11 @@ struct case_strategy_bool {
     using tag_type = bool;
     using repr_type = bool;
 
+    case_strategy_bool(const type* type) {}
+    
     tag_type tag_from_repr(repr_type b) { return b; }
 
-    repr_type from_typed_pattern(const pattern_ptr& pt, const type* type) {
+    repr_type repr_from_pattern(const pattern_ptr& pt) {
         pattern_constr* cpat;
         if(!(cpat = dynamic_cast<pattern_constr*>(pt.get())) ||
                 (cpat->constr != "True" && cpat->constr != "False") ||
@@ -297,12 +300,11 @@ struct case_strategy_bool {
         into.push_back(instruction_ptr(new instruction_slide(1)));
     }
 
-    size_t case_count(const type* type) {
+    size_t case_count() {
         return 2;
     }
 
     void into_instructions(
-            const type* type,
             case_mappings<case_strategy_bool>& ms,
             std::vector<instruction_ptr>& into) {
         if(ms.defined_cases_count() == 0) {
@@ -321,16 +323,23 @@ struct case_strategy_data {
     using tag_type = int;
     using repr_type = std::pair<const type_data::constructor*, const std::vector<std::string>*>;
 
+    const type_data* arg_type;
+
+    case_strategy_data(const type* t) {
+        arg_type = dynamic_cast<const type_data*>(t);
+        assert(arg_type);
+    }
+
     tag_type tag_from_repr(const repr_type& repr) { return repr.first->tag; }
 
-    repr_type from_typed_pattern(const pattern_ptr& pt, const type* type) {
+    repr_type repr_from_pattern(const pattern_ptr& pt) {
         pattern_constr* cpat;
         if(!(cpat = dynamic_cast<pattern_constr*>(pt.get())))
             throw type_error(
                     "pattern cannot be interpreted as constructor.",
                     pt->loc);
         return std::make_pair(
-                &static_cast<const type_data*>(type)->constructors.find(cpat->constr)->second,
+                &arg_type->constructors.find(cpat->constr)->second,
                 &cpat->params);
     }
 
@@ -349,19 +358,17 @@ struct case_strategy_data {
         into.push_back(instruction_ptr(new instruction_slide(repr.second->size())));
     }
 
-    size_t case_count(const type* type) {
-        return static_cast<const type_data*>(type)->constructors.size();
+    size_t case_count() {
+        return arg_type->constructors.size();
     }
 
     void into_instructions(
-            const type* type,
             case_mappings<case_strategy_data>& ms,
             std::vector<instruction_ptr>& into) {
         instruction_jump* jump_instruction = new instruction_jump();
         instruction_ptr inst(jump_instruction);
 
-        auto data_type = static_cast<const type_data*>(type);
-        for(auto& constr : data_type->constructors) {
+        for(auto& constr : arg_type->constructors) {
             if(!ms.case_defined_for(constr.second.tag)) continue;
             jump_instruction->branches.push_back(
                     std::move(ms.get_specific_case_for(constr.second.tag)));
@@ -372,7 +379,7 @@ struct case_strategy_data {
         if(ms.default_case_defined()) {
             jump_instruction->branches.push_back(
                     std::move(ms.get_default_case()));
-            for(auto& constr : data_type->constructors) {
+            for(auto& constr : arg_type->constructors) {
                 if(ms.case_defined_for(constr.second.tag)) continue;
                 jump_instruction->tag_mappings[constr.second.tag] =
                     jump_instruction->branches.size();
@@ -385,29 +392,29 @@ struct case_strategy_data {
 
 template <typename T>
 void compile_case(const ast_case& node, const env_ptr& env, const type* type, std::vector<instruction_ptr>& into) {
-    T strategy;
+    T strategy(type);
     case_mappings<T> cases;
     for(auto& branch : node.branches) {
         pattern_var* vpat;
         if((vpat = dynamic_cast<pattern_var*>(branch->pat.get()))) {
-            if(cases.defined_cases_count() == strategy.case_count(type))
+            if(cases.defined_cases_count() == strategy.case_count())
                 throw type_error("redundant catch-all pattern", branch->pat->loc);
             auto& branch_into = cases.make_default_case();
             env_ptr new_env(new env_var(vpat->var, env));
             branch->expr->compile(new_env, branch_into);
             branch_into.push_back(instruction_ptr(new instruction_slide(1)));
         } else {
-            auto repr = strategy.from_typed_pattern(branch->pat, type);
+            auto repr = strategy.repr_from_pattern(branch->pat);
             auto& branch_into = cases.make_case_for(strategy.tag_from_repr(repr));
             strategy.compile_branch(branch, env, repr, branch_into);
         }
     }
 
-    if(!(cases.defined_cases_count() == strategy.case_count(type) ||
+    if(!(cases.defined_cases_count() == strategy.case_count() ||
                 cases.default_case_defined()))
         throw type_error("incomplete patterns", node.loc);
 
-    strategy.into_instructions(type, cases, into);
+    strategy.into_instructions(cases, into);
 }
 
 void ast_case::compile(const env_ptr& env, std::vector<instruction_ptr>& into) const {