- Use a hash table to canonicalize instances/arrays to avoid having to iterate over a linear list a…

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
diff --git a/runtime/vm/parser.cc b/runtime/vm/parser.cc
index 6848e74497ae76201ed9492029a75659e475ea37..1e9f97f8b83387980c4fec9a7aa54c87acfc620b 100644
--- a/runtime/vm/parser.cc
+++ b/runtime/vm/parser.cc
@@ -12062,7 +12062,7 @@ RawInstance* Parser::TryCanonicalize(const Instance& instance,
   }
   const char* error_str = NULL;
   Instance& result =
-      Instance::Handle(Z, instance.CheckAndCanonicalize(&error_str));
+      Instance::Handle(Z, instance.CheckAndCanonicalize(thread(), &error_str));
   if (result.IsNull()) {
     ReportError(token_pos, "Invalid const object %s", error_str);
   }
@@ -12747,6 +12747,9 @@ AstNode* Parser::ParseListLiteral(TokenPosition type_pos,
 
   if (is_const) {
     // Allocate and initialize the const list at compile time.
+    if ((element_list.length() == 0) && list_type_arguments.IsNull()) {
+      return new(Z) LiteralNode(literal_pos, Object::empty_array());
+    }
     Array& const_list = Array::ZoneHandle(Z,
         Array::New(element_list.length(), Heap::kOld));
     const_list.SetTypeArguments(