diff --git a/src/compiler/prepare_grammar/extract_tokens.cc b/src/compiler/prepare_grammar/extract_tokens.cc
index 7510ff71..c63cb968 100644
--- a/src/compiler/prepare_grammar/extract_tokens.cc
+++ b/src/compiler/prepare_grammar/extract_tokens.cc
@@ -18,7 +18,6 @@
 namespace tree_sitter {
 namespace prepare_grammar {
 
-using std::dynamic_pointer_cast;
 using std::make_shared;
 using std::make_tuple;
 using std::map;
@@ -122,8 +121,8 @@ tuple<InitialSyntaxGrammar, LexicalGrammar, const GrammarError *> extract_tokens
    */
   size_t i = 0;
   for (const Variable &variable : processed_variables) {
-    auto symbol = dynamic_pointer_cast<const Symbol>(variable.rule);
-    if (symbol.get() && symbol->is_token && !symbol->is_built_in() &&
+    auto symbol = variable.rule->as<Symbol>();
+    if (symbol && symbol->is_token && !symbol->is_built_in() &&
         extractor.token_usage_counts[symbol->index] == 1) {
       lexical_grammar.variables[symbol->index].type = variable.type;
       lexical_grammar.variables[symbol->index].name = variable.name;
@@ -160,8 +159,8 @@ tuple<InitialSyntaxGrammar, LexicalGrammar, const GrammarError *> extract_tokens
       continue;
     }
 
-    auto symbol = dynamic_pointer_cast<const Symbol>(rule);
-    if (!symbol.get())
+    auto symbol = rule->as<Symbol>();
+    if (!symbol)
       return make_tuple(syntax_grammar, lexical_grammar,
                         ubiq_token_err(rule->to_string()));
 
diff --git a/src/compiler/rule.cc b/src/compiler/rule.cc
index b4617257..8cb8ce95 100644
--- a/src/compiler/rule.cc
+++ b/src/compiler/rule.cc
@@ -1,5 +1,5 @@
 #include "compiler/rule.h"
-#include <set>
+#include <memory>
 
 namespace tree_sitter {
 
diff --git a/src/compiler/rule.h b/src/compiler/rule.h
index 55cf09e8..2dbe4046 100644
--- a/src/compiler/rule.h
+++ b/src/compiler/rule.h
@@ -22,6 +22,11 @@ class Rule {
   virtual std::string to_string() const = 0;
   virtual void accept(rules::Visitor *visitor) const = 0;
   virtual ~Rule();
+
+  template<typename T>
+  const T * as() const {
+    return dynamic_cast<const T *>(this);
+  }
 };
 
 }  // namespace tree_sitter
diff --git a/src/compiler/rules/blank.cc b/src/compiler/rules/blank.cc
index b5eee146..6348bf62 100644
--- a/src/compiler/rules/blank.cc
+++ b/src/compiler/rules/blank.cc
@@ -13,7 +13,7 @@ rule_ptr Blank::build() {
 }
 
 bool Blank::operator==(const Rule &rule) const {
-  return dynamic_cast<const Blank *>(&rule) != nullptr;
+  return rule.as<Blank>() != nullptr;
 }
 
 size_t Blank::hash_code() const {
diff --git a/src/compiler/rules/character_set.cc b/src/compiler/rules/character_set.cc
index d18808ee..f5618a07 100644
--- a/src/compiler/rules/character_set.cc
+++ b/src/compiler/rules/character_set.cc
@@ -64,7 +64,7 @@ CharacterSet::CharacterSet()
     : includes_all(false), included_chars({}), excluded_chars({}) {}
 
 bool CharacterSet::operator==(const Rule &rule) const {
-  const CharacterSet *other = dynamic_cast<const CharacterSet *>(&rule);
+  const CharacterSet *other = rule.as<CharacterSet>();
   return other && (includes_all == other->includes_all) &&
          (included_chars == other->included_chars) &&
          (excluded_chars == other->excluded_chars);
diff --git a/src/compiler/rules/choice.cc b/src/compiler/rules/choice.cc
index b4b08e9e..975adbef 100644
--- a/src/compiler/rules/choice.cc
+++ b/src/compiler/rules/choice.cc
@@ -10,18 +10,17 @@ using std::string;
 using std::make_shared;
 using std::vector;
 using std::set;
-using std::dynamic_pointer_cast;
 
 Choice::Choice(const vector<rule_ptr> &elements) : elements(elements) {}
 
 void add_choice_element(vector<rule_ptr> *vec, const rule_ptr new_rule) {
-  auto choice = dynamic_pointer_cast<const Choice>(new_rule);
-  if (choice.get()) {
+  auto choice = new_rule->as<Choice>();
+  if (choice) {
     for (auto &child : choice->elements)
       add_choice_element(vec, child);
   } else {
-    for (auto &el : *vec)
-      if (el->operator==(*new_rule))
+    for (auto &element : *vec)
+      if (element->operator==(*new_rule))
         return;
     vec->push_back(new_rule);
   }
@@ -38,7 +37,7 @@ rule_ptr Choice::build(const vector<rule_ptr> &inputs) {
 }
 
 bool Choice::operator==(const Rule &rule) const {
-  const Choice *other = dynamic_cast<const Choice *>(&rule);
+  const Choice *other = rule.as<Choice>();
   if (!other)
     return false;
   size_t size = elements.size();
diff --git a/src/compiler/rules/metadata.cc b/src/compiler/rules/metadata.cc
index d3d56748..63334a2e 100644
--- a/src/compiler/rules/metadata.cc
+++ b/src/compiler/rules/metadata.cc
@@ -13,8 +13,12 @@ using std::map;
 Metadata::Metadata(rule_ptr rule, map<MetadataKey, int> values)
     : rule(rule), value(values) {}
 
+rule_ptr Metadata::build(rule_ptr rule, map<MetadataKey, int> values) {
+  return std::make_shared<Metadata>(rule, values);
+}
+
 bool Metadata::operator==(const Rule &rule) const {
-  auto other = dynamic_cast<const Metadata *>(&rule);
+  auto other = rule.as<Metadata>();
   return other && other->value == value && other->rule->operator==(*this->rule);
 }
 
diff --git a/src/compiler/rules/metadata.h b/src/compiler/rules/metadata.h
index 48b856cc..d93bbc9f 100644
--- a/src/compiler/rules/metadata.h
+++ b/src/compiler/rules/metadata.h
@@ -19,6 +19,7 @@ enum MetadataKey {
 class Metadata : public Rule {
  public:
   Metadata(rule_ptr rule, std::map<MetadataKey, int> value);
+  static rule_ptr build(rule_ptr rule, std::map<MetadataKey, int> value);
 
   bool operator==(const Rule &other) const;
   size_t hash_code() const;
diff --git a/src/compiler/rules/named_symbol.cc b/src/compiler/rules/named_symbol.cc
index b5afe89f..d846580b 100644
--- a/src/compiler/rules/named_symbol.cc
+++ b/src/compiler/rules/named_symbol.cc
@@ -11,7 +11,7 @@ using std::hash;
 NamedSymbol::NamedSymbol(const std::string &name) : name(name) {}
 
 bool NamedSymbol::operator==(const Rule &rule) const {
-  auto other = dynamic_cast<const NamedSymbol *>(&rule);
+  auto other = rule.as<NamedSymbol>();
   return other && other->name == name;
 }
 
diff --git a/src/compiler/rules/pattern.cc b/src/compiler/rules/pattern.cc
index 83d44698..5ac8f97b 100644
--- a/src/compiler/rules/pattern.cc
+++ b/src/compiler/rules/pattern.cc
@@ -12,7 +12,7 @@ using std::hash;
 Pattern::Pattern(const string &string) : value(string) {}
 
 bool Pattern::operator==(tree_sitter::Rule const &other) const {
-  auto pattern = dynamic_cast<const Pattern *>(&other);
+  auto pattern = other.as<Pattern>();
   return pattern && (pattern->value == value);
 }
 
diff --git a/src/compiler/rules/repeat.cc b/src/compiler/rules/repeat.cc
index 40f41ed3..64d793bb 100644
--- a/src/compiler/rules/repeat.cc
+++ b/src/compiler/rules/repeat.cc
@@ -6,22 +6,21 @@
 namespace tree_sitter {
 namespace rules {
 
-using std::dynamic_pointer_cast;
 using std::make_shared;
 using std::string;
 
 Repeat::Repeat(const rule_ptr content) : content(content) {}
 
 rule_ptr Repeat::build(const rule_ptr &rule) {
-  auto inner_repeat = dynamic_pointer_cast<Repeat>(rule);
-  if (inner_repeat.get())
-    return inner_repeat;
+  auto inner_repeat = rule->as<Repeat>();
+  if (inner_repeat)
+    return rule;
   else
     return make_shared<Repeat>(rule);
 }
 
 bool Repeat::operator==(const Rule &rule) const {
-  const Repeat *other = dynamic_cast<const Repeat *>(&rule);
+  auto other = rule.as<Repeat>();
   return other && (*other->content == *content);
 }
 
diff --git a/src/compiler/rules/seq.cc b/src/compiler/rules/seq.cc
index 54dc5821..cc934a5c 100644
--- a/src/compiler/rules/seq.cc
+++ b/src/compiler/rules/seq.cc
@@ -2,6 +2,7 @@
 #include <string>
 #include "compiler/rules/visitor.h"
 #include "compiler/rules/blank.h"
+#include "compiler/rules/metadata.h"
 
 namespace tree_sitter {
 namespace rules {
@@ -14,14 +15,25 @@ Seq::Seq(rule_ptr left, rule_ptr right) : left(left), right(right) {}
 
 rule_ptr Seq::build(const std::vector<rule_ptr> &rules) {
   rule_ptr result = make_shared<Blank>();
-  for (auto &rule : rules)
-    result = (typeid(*result) != typeid(Blank)) ? make_shared<Seq>(result, rule)
-                                                : rule;
+  for (auto &rule : rules) {
+    auto blank = rule->as<Blank>();
+    if (blank)
+      continue;
+
+    auto metadata = rule->as<Metadata>();
+    if (metadata && metadata->rule->as<Blank>())
+      continue;
+
+    if (result->as<Blank>())
+      result = rule;
+    else
+      result = make_shared<Seq>(result, rule);
+  }
   return result;
 }
 
 bool Seq::operator==(const Rule &rule) const {
-  const Seq *other = dynamic_cast<const Seq *>(&rule);
+  const Seq *other = rule.as<Seq>();
   return other && (*other->left == *left) && (*other->right == *right);
 }
 
diff --git a/src/compiler/rules/string.cc b/src/compiler/rules/string.cc
index 075a4267..8a77b169 100644
--- a/src/compiler/rules/string.cc
+++ b/src/compiler/rules/string.cc
@@ -11,7 +11,7 @@ using std::hash;
 String::String(string value) : value(value) {}
 
 bool String::operator==(const Rule &rule) const {
-  const String *other = dynamic_cast<const String *>(&rule);
+  auto other = rule.as<String>();
   return other && (other->value == value);
 }
 
diff --git a/src/compiler/rules/symbol.cc b/src/compiler/rules/symbol.cc
index 33472874..cdfb78cf 100644
--- a/src/compiler/rules/symbol.cc
+++ b/src/compiler/rules/symbol.cc
@@ -19,7 +19,7 @@ bool Symbol::operator==(const Symbol &other) const {
 }
 
 bool Symbol::operator==(const Rule &rule) const {
-  const Symbol *other = dynamic_cast<const Symbol *>(&rule);
+  auto other = rule.as<Symbol>();
   return other && this->operator==(*other);
 }