Create ambiguity nodes when joining stack heads

src/compiler/build_tables/build_parse_table.cc

@@ -69,6 +69,7 @@ class ParseTableBuilder {
 
     parse_table.symbols.insert(rules::ERROR());
     parse_table.symbols.insert(rules::DOCUMENT());
+    parse_table.symbols.insert(rules::AMBIGUITY());
 
     return { parse_table, nullptr };
   }

src/compiler/generate_code/c_code.cc

@@ -315,8 +315,12 @@ class CCodeGenerator {
         return "ts_builtin_sym_error";
       else if (symbol == rules::END_OF_INPUT())
         return "ts_builtin_sym_end";
-      else
+      else if (symbol == rules::DOCUMENT())
         return "ts_builtin_sym_document";
+      else if (symbol == rules::AMBIGUITY())
+        return "ts_builtin_sym_ambiguity";
+      else
+        return "";
     } else {
       string name = sanitize_name(rule_name(symbol));
       if (symbol.is_auxiliary())

src/compiler/rules/built_in_symbols.cc

@@ -7,6 +7,7 @@ Symbol END_OF_INPUT() { return Symbol(-1, SymbolOptionToken); }
 Symbol ERROR() { return Symbol(-2, SymbolOptionToken); }
 Symbol START() { return Symbol(-3); }
 Symbol DOCUMENT() { return Symbol(-4); }
+Symbol AMBIGUITY() { return Symbol(-5); }
 
 }  // namespace rules
 }  // namespace tree_sitter

src/compiler/rules/built_in_symbols.h

@@ -10,6 +10,7 @@ Symbol ERROR();
 Symbol START();
 Symbol END_OF_INPUT();
 Symbol DOCUMENT();
+Symbol AMBIGUITY();
 
 }  // namespace rules
 }  // namespace tree_sitter