1 files changed, 32 insertions, 5 deletions

diff --git a/src/grammar.cc b/src/grammar.cc
index 25c4d64..6ed2766 100644
--- a/src/grammar.cc
+++ b/src/grammar.cc
@@ -127,11 +127,6 @@ class GrammarLoader {
     auto it = second_pass_elements.begin();
     for (auto const& pair : first_pass_elements) {
       auto const& element = *it++;
-      if (pair.second.definitions.empty()) {
-        errors_.err(pair.second.loc,
-                    std::format("No definitions for {}", pair.first));
-        continue;
-      }
       std::vector<std::string_view> in_symbols;
       for (auto const& in_definition : pair.second.definitions) {
         str::split(in_definition, in_symbols);
@@ -247,10 +242,42 @@ class GrammarLoader {
           "No root element found");
     }
 
+    optimize(second_pass_elements);
+
     return std::make_unique<GrammarImpl>(std::move(second_pass_elements));
   }
 
  private:
+  static void optimize(std::vector<std::unique_ptr<Element>> const& elements) {
+    merge_terminals(elements);
+  }
+
+  static void merge_terminals(std::vector<std::unique_ptr<Element>> const& elements) {
+    for (auto const& element : elements) {
+      for (auto& definition : element->definitions) {
+        auto it = definition.symbols.begin();
+        while (it != definition.symbols.end()) {
+          if (it->type != Symbol::Type::kTerminal) {
+            ++it;
+            continue;
+          }
+
+          auto it2 = it + 1;
+          if (it2 == definition.symbols.end())
+            break;
+          if (it2->type != Symbol::Type::kTerminal ||
+              it->optional != it2->optional) {
+            ++it;
+            continue;
+          }
+
+          it->value += it2->value;
+          definition.symbols.erase(it2);
+        }
+      }
+    }
+  }
+
   std::unique_ptr<line::Reader> reader_;
   std::vector<std::string> const& character_classes_;
   src::Errors& errors_;